Innovative green nanotechnology for sustainable water purification under climate change: tackling antibiotic contaminants

Abstract

Antibiotic contamination represents a pressing environmental crisis affecting aquatic ecosystems globally, a challenge that climate change only intensifies. Key culprits of this pollution include pharmaceutical discharges, agricultural runoff, and improper waste disposal. These antibiotics persist in our water systems due to their stable chemical structures, while climate-related factors like rising temperatures and extreme weather can exacerbate their impact. The accumulation of these substances poses significant threats to aquatic life, human health, and the broader environment, as they facilitate the alarming spread of antimicrobial resistance among microorganisms. Unfortunately, traditional water treatment methods remain largely ineffective against these stubborn pollutants. In response to this growing issue, green nanotechnology emerges as a promising and sustainable solution. By harnessing plant extracts, microbes, and agricultural waste for the synthesis of nanoparticles, this approach minimizes environmental harm while effectively addressing contamination. Metal oxide nanoparticles, carbon-based materials, and biopolymeric nanomaterials have proven to be highly efficient in eliminating antibiotics through processes such as adsorption, photodegradation, and redox reactions. However, the effectiveness and applicability of these nanoparticles under varying climate conditions warrant further exploration. This review highlights the transformative potential of green nanotechnology for safe and sustainable water remediation. It underscores recent advancements in eco-friendly nanomaterials, elucidating their removal mechanisms, environmental behavior, and the critical need for climate-resilient, safe-by-design strategies. To combat antibiotic pollution effectively amid shifting climatic conditions, we must investigate green nanotechnology for future water treatment practices. This proactive approach not only safeguards our water systems but also ensures a healthier future for both aquatic ecosystems and human communities.

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Environmental significance

Green nanotechnology represents a transformative and sustainable approach to tackling climate-driven antibiotic contamination, utilizing eco-friendly nanomaterials to efficiently remove pollutants, safeguard aquatic ecosystems, and protect human health through resilient and safe-by-design water remediation strategies.

1. Introduction

Antibiotic residues have become one of the major contaminants in the water system and soil worldwide. These antibiotics are widely used not only in human healthcare but also in veterinary care and agriculture.^1,163 The presence of these antibiotic contaminants in the natural environment is due to different pathways, including excretions from humans and animals, the pharmaceutical industry, hospital effluents, improper disposal of unused medicines and run-offs from aquaculture, agricultural and livestock farm lands.¹ These residues not only act as pollutants but also exert selective stress on microbial communities, which accelerates the emergence and spread of antimicrobial resistance (AMR) by being biologically active and contributing to the proliferation of antibiotic-resistant bacteria (ARB). Multidrug-resistant tuberculosis (MDR-TB), methicillin-resistant Staphylococcus aureus (MRSA) and extended-spectrum β-lactamase (ESBL) producing Enterobacteriaceae are common examples of AMR pathogens.² AMR is a major global health risk that occurs due to the ability of microorganisms such as bacteria, viruses, fungi, etc. to survive against the effective antimicrobial treatments, including antibiotics.³ According to the World Health Organization (WHO) reports in 2022, AMR is classified as one of the greatest threats to human health, which approximately causes 700 000 deaths annually as a result of infections caused by antimicrobial-resistant microorganisms.⁴

Climate change and AMR are cross-linked global concerns that threaten the health of living organisms and the environment.⁵ Climate change adds a complex layer of stress to already susceptible ecosystems. Climate change, such as rising temperatures, altered precipitation patterns, increased frequency of floods and droughts, and changing hydrological cycles, intensifies the health risks by changing the mobility, concentration, transformation, and bioavailability of antibiotic residues in soil and water systems.⁵ As an example, heavy rainfall can cause combined sewer overflows, increasing the discharge of untreated or partially treated effluents into surface waters. Warmer temperatures may accelerate microbial activity and resistance gene exchange, while drought conditions can reduce dilution capacity, leading to higher contaminant loads in water bodies.⁶ These combined stressors increase the environmental and public health risks associated with antibiotic contamination by increasing the risk of AMR development, biodiversity loss and human exposure through water and food chains.⁶

There are many types of conventional treatment methods, including filtration, ozonation, and chlorination for the purification of wastewater and drinkable water.⁷ These methods are inadequate and inefficient in removing emerging contaminants, including antibiotic residues, as they do not effectively degrade these complex compounds or may produce toxic byproducts.⁸ These treatment systems may be challenged due to the variable flow rates, energy limitations and increasing contaminant loads caused by climate change.⁹ There is an urgent need for adaptive, low-energy and environmentally friendly technologies to overcome these challenges.

Fig. 1 illustrates the interactions among key themes discussed in the manuscript. Antibiotics such as tetracyclines, sulfonamides, and fluoroquinolones are targeted by nanomaterial-based water treatment technologies. The efficacy of these treatments is influenced by climate stressors, including UV exposure, temperature, pH, salinity, and extreme events, which can alter removal kinetics, adsorption capacity, and overall performance. The framework also highlights current knowledge gaps, including long-term performance, formation of degradation byproducts, and life-cycle effects. Together, this schematic provides a roadmap for understanding how antibiotics, nanomaterials, and environmental stressors intersect to influence water purification outcomes.

Fig. 1 Conceptual framework of antibiotic removal using nanomaterial-based water treatment under climate stressors. Source: created by the author using Canva elements (http://www.canva.com).

Green nanotechnology is the use of nanomaterials that are synthesised using environmentally friendly methods. This concept presents a viable path forward to address the problems of pollution and climate challenges by combining efficiency with sustainability.¹⁰ Green synthesised nanoparticles and nanocomposites offer unique physicochemical properties, including high surface area and reactivity, allowing efficient degradation, high adsorptive and catalytic properties and the capability to convert antibiotic pollutants without introducing additional secondary environmental hazards.¹⁰

An important, yet underaddressed, dimension is the climate resilience of these green nanomaterials. Climate-resilient nanomaterials are those engineered to maintain structural integrity and functional efficacy under environmental stresses such as shifts in temperature, wide pH ranges, and varying salinity. Unlike conventional green nanomaterials, which primarily emphasize non-toxic synthesis and biodegradability, climate-resilient nanomaterials are explicitly engineered to withstand dynamic environmental conditions expected under climate change, ensuring long-term stability and functionality in real-world water treatment settings. Measurable indicators of resilience include thermal stability, such as resistance to aggregation or performance loss under elevated or fluctuating temperatures; pH stability, shown by retention of adsorption capacity, maintenance of surface charge, and minimal dissolution or structural alteration over the acid–alkaline spectrum; and salinity tolerance, evidenced by stable dispersion and negligible functional decline in brackish or saline waters. Some recent studies already illustrate progress: silica nanoparticles modified with hydrophilic silanes remain thermally stable in 3.5% NaCl brine at 60 °C over a month, indicating promising salinity and thermal resilience.¹⁷¹ Green synthesised carbon dots from Aloe vera show pH-stable fluorescence and structure in both acidic and neutral media, suggesting possible robust behavior under pH variability.¹⁷²

Table 1 presents a concise summary of quantitative resilience metrics for selected nanomaterials, including parameters such as thermal stability, pH tolerance, salinity limits, and biological recovery. These research data provide a benchmark for assessing and comparing the climate-resilience potential of nanomaterials, thereby informing the design and testing of future systems under environmental stress.

Table 1 Resilience indicators for nanomaterials

Nanomaterial	Resilience metric	Quantitative value/range	Interpretation	Reference
Silica nanoparticles (hydrophilic)	Thermal & salinity stability	Stable for about 1 day at 80 °C in 42 g L^−1 NaCl (4.2% w/v)	In silica nanofluids, high ionic strength strongly destabilizes; but at low pH (≈1.5), stability extends to around 3 weeks	213
	pH tolerance	Very low pH near the isoelectric point (IEP ∼2–3.5) improves stability in brine	At very acidic pH (close to IEP) and high salt, steric/hydration repulsion helps stabilize silica	213
Carbon nanotubes (CNTs)	Thermal stability	Stable up to 500 °C (e.g., CNTs coated with mesoporous silica; metal sintering not observed at 500 °C)	For CNT-based catalysts, a silica shell prevents agglomeration even at high temperatures	214
	Colloidal/rheological stability	Maintain colloidal stability in hydrocarbon-based drilling fluids exposed to 150 °C during thermal ageing tests	In drilling-fluid systems, adding 0.1 wt% single-walled CNT reduces destabilization rate. CNTs help stabilize emulsions even under high temperature	215
Quantum dots (QD) (CdSe/CdSe–ZnS)	pH stability	Linear sensor response from pH 2 to 12 (CdSe/ZnS QD in an EIS sensor)	This shows that certain QDs retain functional stability in a very broad pH range	216
	Ionic strength (aggregation)	Stability/aggregation kinetics strongly depend on ionic strength/electrolyte type	In a colloidal study, CdSe–ZnS QDs aggregated depending on salt concentration and electrolyte	217
Carbon quantum dots (CQDs)	Colloidal stability (pH)	Best stability at pH 7.4, moderate at pH 7.2, and worst at pH 4.1	CQDs showed decreased colloidal stability in acidic pH, likely due to protonation of their functional surface groups	218
Polymeric nanocomposites/gels	High temperature, high salinity stability	Some polymer nanocomposites remain stable in high temperature, high salinity, and extreme pH when properly stabilized	Polymers stabilized via cross-linking, or with appropriate backbone design, can resist degradation or aggregation under harsh conditions	219
Silica nanoparticles	Thermal stability	60 °C for 1 month	In 3.5% NaCl brine and synthetic seawater (SSW), silane + GLYMO-modified silica remained stable, without aggregation for 1 month at 60 °C	171
	Salinity tolerance	3.5% NaCl (w/v)	The same system maintained colloidal stability at high salinity	171
	pH tolerance	pH 4–7	Stability of the modified silica nanoparticles was demonstrated over pH 4–7 under the above salinity and temperature	171

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Despite the promising potential of green nanotechnology in water purification, several critical research gaps hinder its widespread application. Key challenges include insufficient climate resilience, as many nanomaterials exhibit reduced efficacy under varying environmental conditions.¹¹ Additionally, engineering complexities arise in scaling up green nanoparticle (NP) synthesis and integrating them into existing water treatment infrastructures. Environmental impact assessments remain limited, particularly concerning the long-term effects of nanomaterial release into aquatic ecosystems. Furthermore, there is a lack of standardized protocols for evaluating the performance and safety of green NPs, leading to inconsistencies in research findings. Addressing these gaps is essential to realize the full potential of green nanotechnology in sustainable water purification.²¹²

Recent reviews have extensively covered antibiotic contamination and the use of green nanomaterials for water purification.¹¹ However, these studies largely focus on individual aspects such as material synthesis, pollutant removal efficiency, or laboratory-scale applications, with limited attention to climate-related challenges. In contrast, the present review provides a comprehensive perspective that integrates the environmental and public health implications of antibiotic contamination, how climate changes affect sustainable water purification, and the integration of climate resilience with green nanotechnology.

This review highlights the role of biocompatible, multifunctional nanoparticles derived from renewable resources in mitigating antibiotic contamination under changing climatic conditions. Emphasising a safe-by-design approach, it integrates climate resilience with green nanotechnology to reduce pollution and ecological risks. By combining insights from environmental science and nanotechnology, the review advocates for eco-friendly strategies to address antibiotic pollution and antimicrobial resistance in a warming world.

Fig. 2 explains that household wastewater, pharmaceutical manufacturing plants, agricultural farmlands and livestock farms are the major sources of antibiotic contaminants. Due to climate change, including elevated temperatures and extreme weather events, these antibiotic contaminants are concentrated in reservoirs and groundwater system. This water is treated using conventional treatment plants, which are not adequate to remove antibiotic contaminants in water. However, the treated water contains antibiotic residues and antibiotic-resistant bacteria. Researchers have been growing attention to develop green synthesised nanomaterials to remove these contaminants from water. Finally, integration of green nanotechnology with wastewater treatment provides safe water for consumption.

Fig. 2 Graphical illustration of the review. Source: created by the author using Canva elements (http://www.canva.com).

2. Antibiotics: a major contaminant in the water system

Antibiotics are a complex group of medicines that are used to treat bacterial infections in humans, animals and agricultural systems.¹⁹ Antibiotics have emerged as significant pollutants in aquatic environments due to their widespread and often unregulated use in human medicine, agriculture, and aquaculture.^12,13 A substantial portion of administered antibiotics, ranging from 30% to 90% is excreted unmetabolized or as active metabolites, entering water systems through municipal sewage and agricultural runoff.¹⁴ Conventional wastewater treatment plants (WWTPs) are typically ineffective in removing these compounds, allowing them to persist in treated effluents discharged into rivers, lakes, and coastal waters.^15,18 A wide variety of antibiotics, including β-lactams, sulfonamides, tetracyclines, fluoroquinolones and macrolides, have been frequently detected in surface waters, groundwaters, and even drinking water sources at concentrations ranging from nanograms to several micrograms per litre.^16,30 These findings bring attention to the chronic and global nature of antibiotic contamination in aquatic ecosystems, affecting not only human beings but also animals and the environment.³² While many pollutants degrade or dilute over time, antibiotics are capable of being biologically active at low concentrations and exert selective stress on environmental microbiota, which is particularly concerning given their role in the evolution of antimicrobial resistance.¹⁷ The complex mixture of antibiotics and other co-contaminants in these water systems challenges conventional water treatment techniques, and urgent attention is needed for enhanced wastewater treatment strategies and regulatory frameworks, which are focused specifically on emerging pharmaceutical contaminants.¹⁸

Depending on their chemical structure and mechanism of action, these antibiotics are classified into several types.²⁰ β-lactams are one of the most widely used classes of antibiotics in both human and veterinary medicines, which include antibiotics such as penicillins, cephalosporins, carbapenems, monobactams, etc.²¹ These β-lactams inhibit the synthesis of bacterial cell wall. They are commonly used in a multitude of infections, including respiratory, urinary tract and skin infections.²¹ Tetracyclines inhibit protein synthesis and are used in both human medicine and livestock farming, while sulfonamides are used in the treatment of urinary and gastrointestinal infections.²² Fluoroquinolones such as ciprofloxacin, norfloxacin act by inhibiting DNA replication and are applied in both clinical and veterinary settings.²³ Macrolides, including erythromycin, clarithromycin and azithromycin, target protein synthesis and are used for respiratory and soft tissue infections.²⁴

The presence of antibiotics in water systems poses significant ecological and public health risks. These substances can exert selective pressure on microbial communities, promoting the development of AMR and the spread of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs). Such resistance can compromise the efficacy of existing treatments for both human and veterinary infections, leading to increased morbidity and mortality. A study conducted in Sri Lanka has investigated the contribution of sources of antibiotic contaminants, including the unregulated use of antibacterial drugs in plant protection, animal husbandry, aquaculture, veterinary medicine and human therapy, to the increased prevalence of antibiotic-resistant bacteria in the environment.^28,29 That study recorded that antibiotic residues and resistant bacteria in surface and groundwater aquifers and pristine environments as well.^13,29

The residues of these antibiotics are transported via municipal wastewater systems to wastewater treatment plants (WWTPs), where conventional biological treatment methods are applied for the removal of these antibiotic contaminants.²⁵ Due to the inefficiency of these conventional treatment methods, antibiotic residues enter the receiving surface waters.²⁶ Several monitoring studies have reported the occurrence of commonly used antibiotics such as sulfamethoxazole, trimethoprim, ciprofloxacin, tetracycline, and amoxicillin with concentrations ranging from ng L⁻¹ to several μg L⁻¹ in rivers, lakes, and even drinking water sources.²⁷ These findings highlight the widespread and continuous loading of diverse antibiotic classes into aquatic systems and the need for improved management of their environmental release.

A study conducted in Sri Lanka recorded the presence of antibiotics, including 5 μg L⁻¹ of oxytetracyclines, 4 μg L⁻¹ of tetracyclines and 3 μg L⁻¹ of amoxicillin in the wastewater discharge drains in large-scale livestock and poultry farms.¹⁶⁴ Additionally, aquaculture effluents contain higher concentrations of antibiotics, including tetracyclines and oxytetracyclines. As an example, oxytetracyclines were detected in effluents from shrimp hatcheries, food fish farms and ornamental fish farms in 56 ± 1 μg L⁻¹ to 234 ± 14 μg L⁻¹, 8 ± 12 μg L⁻¹ to 221 ± 12 μg L⁻¹, and 9 ± 11 μg L⁻¹ to 31 ± 5 μg L⁻¹, respectively.¹³ The same study detected tetracycline concentrations of 12 ± 19 μg L⁻¹ to 112 ± 17 μg L⁻¹ in shrimp hatcheries, 1 ± 2 μg L⁻¹ to 2 ± 31 μg L⁻¹ in ornamental fish farms, and 1 ± 31 μg L⁻¹ to 76 ± 22 μg L⁻¹ in food fish farms. A study conducted to detect antibiotic residues in effluents released from aquaculture farms in Thailand reported that the concentrations of erythromycin and tetracyclines were up to 0.18 μg L⁻¹.²⁹ Likewise, most of the studies worldwide have recorded the presence of antibiotic residues in various water systems while highlighting the emergent need of better treatment methods to address these issues.

2.1 Sources of antibiotic contaminants in the environment

Table 2 shows the common sources of antibiotic contaminants and examples of antibiotics found in the environmental system worldwide. Collectively, the sources mentioned in Table 2 result in the continuous release of antibiotics into terrestrial and aquatic environments, establishing hotspots for the emergence and spread of antibiotic resistance and posing significant challenges to current treatment and regulatory systems.

Table 2 Sources of antibiotic contaminants

Source	Pathway/mechanism	Examples of antibiotics	Environmental impact	Reference
Human and animal excretion	Excretion into sewage or manure by incomplete metabolism	General classes (e.g., ciprofloxacin, erythromycin)	Discharge of effluents and biosolids into natural systems and spread AMR	14, 15
Municipal wastewater treatment plants (WWTPs)	Ineffective removal during treatment	Ciprofloxacin, erythromycin, sulfamethoxazole, tetracyclines	Discharge of effluents and biosolids into natural systems and spread AMR	15, 16, 27
Livestock farming	Use of antibiotics for growth & disease prevention, excretion in manure, and application as fertilizer	Oxytetracycline, tetracyclines	Leaching into water systems via rain or irrigation and spreading AMR	22, 164
Aquaculture	Direct addition to feed/water, excretions and uneaten feed release antibiotics into the water	Tetracyclines	Contaminates sediments and aquatic ecosystems	165
Hospital and veterinary wastewater	Discharge of unused/partially metabolized drugs from medical facilities	Multiple antibiotic classes	Discharge of effluents and biosolids into natural systems and WWTPs	164, 165
Improper disposal of unused medicines	Throwing into the regular garbage or flushing into toilets	General classes	Leads to leaching into soil and water	167
Agricultural plant protection	Off-label use of antibiotics in crops	Streptomycin, oxytetracycline	Contributes to soil and water contamination	166
Poultry farms	Use of antibiotics for growth & disease prevention, excretion in manure, and application as fertilizer	Tetracyclines	Leaching into water systems via rain or irrigation	164

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2.2 Environmental behavior of antibiotic residues

Antibiotic residues in the environment undergo various processes, including sorption, photodegradation, hydrolysis, and biodegradation, that influence their persistence and impact (Table 3).³³

Fig. 3 indicates the different processes, such as sorption, photolysis, hydrolysis and biodegradation, that antibiotic residues undergo when they enter the environment. Sorption is a combination of adsorption and absorption mechanisms through which contaminants such as antibiotics interact with soil and sediment particles.³⁴ Antibiotics like fluoroquinolones and tetracyclines readily bind to soil and sediment particles due to their affinity for organic matter and metal ions. For instance, ciprofloxacin achieves rapid sorption to sediment particles, with equilibrium reached within hours. However, its retention efficiency is significantly affected by pH and ionic strength.^33–35 Photodegradation is a significant abiotic process for the removal of sulfonamides, macrolides, and fluoroquinolones.³⁶ Indirect photolysis via hydroxyl radicals and excited triplet state dissolved organic matter plays a crucial role. In estuarine systems, photodegradation is dominant as sorption reduces aqueous concentrations. The presence of natural organic matter and suspended particles increases photolysis rates in natural waters.³⁷ Hydrolysis plays a relatively minor role for most antibiotics due to the stable chemical structures of most antibiotics. Hydrolysis is a minor process related to antibiotics, though some β-lactams may degrade more readily under alkaline conditions.³⁸ Biodegradation is an important biological process in wastewater treatment systems. The removal efficiencies of these systems can be altered widely due to the structure of the compound and system design. Studies have demonstrated that conventional activated sludge processes remove nearly 50–80% of macrolides but are less efficient in the removal of fluoroquinolones and tetracyclines, which can persist in effluents and sludge.^39,40 Antibiotics such as sulfamethoxazole and chlortetracycline possess the ability for bioaccumulation and chronic exposure risks in biosolid-modified agricultural soils.⁴¹

Fig. 3 Environmental behavior of antibiotic residues: source: created by the author using Canva elements (http://www.canva.com).

Table 3 Transformation mechanisms of common antibiotic classes in the environment

Antibiotic class	Sorption potential	Photodegradation	Hydrolysis	Biodegradation efficiency	Key influencing factors
Fluoroquinolones	High	Moderate	Low	Low	pH, ionic strength, organic matter^33
Tetracyclines	High	Low	Low	Low–moderate	Metal ions, sediment composition^33
Sulfonamides	Low–moderate	High	Low	Moderate	Sunlight^36
Macrolides	Moderate	Moderate–high	Low	Moderate–high	Temperature, sludge retention time^36,39
β-Lactams	Low	Low	High (alkaline)	Variable	pH, enzymatic activity in WWTPs^38,39

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2.3 Risk of antibiotic contaminants to human health and aquatic life

According to a recent UN report, the most prevalent water quality challenge is nutrient loading, industrial and anthropogenic activities, and unregulated uses and disposal of antibiotics and other xenobiotic chemicals, which frequently lead to deterioration of the surface and groundwater quality.⁴² A wide spectrum of antibiotics is used in human medication, animal therapy, fish farms, and the agriculture sector, etc., as chemotherapy for controlling infectious diseases.¹³ However, pathogenic bacteria possess the ability to survive under antibiotic exposure by developing resistance against antibiotics.⁴³

Antibiotic contamination in aquatic environments has an impact on not only the ecosystem stability but also the human health.¹³ Even at residual antibiotic concentrations, these antibiotic contaminants disrupt native microbial communities and promote selection of antibiotic-resistant bacteria (ARB) by facilitating horizontal gene transfer (HGT) of antibiotic resistance genes (ARGs) among environmental and pathogenic microbes.^31,43 Several investigations have identified ARGs that confer resistance to antibiotic agents such as β-lactams, fluoroquinolones and tetracyclines in surface waters, sediments and drinking water sources.⁴⁴ A study conducted in Sri Lanka detected 5–15% of surface water with penicillin-resistant genes (bla_TEM, bla_OXA, OPR D, amp a, amp b) and 10% of ground water samples with tetracycline resistance genes (tet A, tet M, tet S, tet B) related to the water samples collected from the Kelani river.¹⁷⁰ These resistant pathogens re-enter human populations via different ways, including recreational water use, consumption of contaminated seafood or irrigation of crops with reclaimed water.⁴⁵

Table 4 shows the environmental residues of antibiotics that cause a potential toxicological risk on susceptible groups, including infants, pregnant women, and immunocompromised individuals. Long-term exposure to low concentrations of these compounds, often through contaminated food or drinking water, has been linked to disruptions in the gut microbiome. Some studies recorded that even trace amounts of antibiotics like tetracyclines and macrolides can change the composition of intestinal bacteria and lead to reduced microbial diversity.⁴⁶ Those antibiotic residues contribute to inflammation and metabolic disorders.⁴⁶ Further, chronic exposure to complex mixtures of antibiotics may produce synergistic effects that enhance overall toxicity and modulate gene expression associated with carcinogenicity and endocrine disruption.⁴⁷

Table 4 Environmental and biological effects of antibiotic contamination

Category	Examples	Impacts	References
Human health risks	Tetracycline, macrolides in water/food	Gut dysbiosis, reduced immunity, endocrine disruption, and AMR development	14, 51–54
Microbial disruption	Sulfamethoxazole, erythromycin, oxytetracycline	Impaired enzyme function, reduced biomass, and ARG transfer	48–50, 57
ARG transmission pathways	blaCTX-M, mcr-1, NDM-1 genes via plasmids	Spread of resistance in hospitals and communities	54, 169
Aquatic organism effects	Ciprofloxacin, erythromycin, sulfamethoxazole	Oxidative stress, immunosuppression, endocrine/reproductive toxicity	55, 56
Ecological impacts	Antibiotic accumulation in sediment and organisms	Bioaccumulation, biomagnification, and reduced biodiversity	56, 60, 61
Disruption of ecosystem services	Alteration of microbial biofilms and nitrifying bacteria	Eutrophication, hypoxia, food web collapse	58, 59

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There is also increasing concern about the transfer of antibiotic resistance genes (ARGs) from environmental microbes to human pathogens via mobile genetic elements such as plasmids and transposons. Wastewater-derived ARGs have been found in clinical isolates of Escherichia coli, Klebsiella pneumoniae, and Acinetobacter baumannii, suggesting that environmental exposures can directly contribute to multidrug-resistant infections.⁴⁸ ARGs such as blaCTX-M, mcr-1, and NDM-1, originally detected in environmental samples, have now been identified in hospital outbreaks worldwide, emphasizing the public health threat posed by unchecked environmental dissemination.^54,169 This gene flow increases the likelihood of community-acquired infections that are difficult to treat, requiring last-resort antibiotics such as colistin or carbapenems, which themselves are increasingly compromised by resistance mechanisms.⁵⁴ Without stronger surveillance and control of environmental ARGs, the effectiveness of antimicrobial therapies may continue to erode, with serious consequences for modern medicine.

Aquatic organisms are also at massive risk. Physiological and developmental impairments in fish, amphibians and invertebrates may occur due to the continuous exposure to antibiotics. Studies have shown that antibiotics such as sulfamethoxazole, ciprofloxacin and erythromycin can cause oxidative stress, immunosuppression, endocrine disruption and reproductive toxicity in non-target species.⁴⁹ These effects impact biodiversity and compromise ecological functions, including food web dynamics and nutrient cycling. Additionally, bioaccumulation of antibiotics in aquatic organisms raises concerns over biomagnification through trophic levels, ultimately impacting human consumers.⁵⁰

The enduring presence and harmful nature of antibiotic residues, along with their contribution to antimicrobial resistance (AMR), highlight the critical necessity for thorough risk evaluations, enhanced wastewater treatment technologies and international regulatory frameworks to mitigate their environmental discharge.⁵⁰ Without immediate interventions, antibiotic contamination could undermine both environmental health and the effectiveness of modern medicine.

Apart from their toxic effects on human health, antibiotic contaminants also cause substantial threats to ecological processes by disrupting the structural and functional integrity of microbial and trophic networks in aquatic ecosystems.⁴⁹ Microbial biofilms play an important role in processes such as nutrient cycling, organic matter breakdown and primary production. These microbial biofilms are particularly susceptible to antibiotics such as oxytetracycline, erythromycin and sulfamethoxazole. Due to the prolonged exposure to these substances, essential ecosystem services become impaired by inhibiting microbial enzyme functions, reducing overall biomass and changing species composition.⁵¹ As an example, disruption in nitrogen cycling, triggering eutrophication and hypoxic conditions, can occur by the interference with nitrifying bacterial populations in sediments.⁵² Additionally, some research investigated the ability of sulfonamides to decline populations of algae and cyanobacteria, thereby reporting that oxygen production was reduced and food resources for organisms at higher trophic levels were limited.⁵³

Antibiotic contamination can also affect the aquatic food webs by disrupting trophic interactions and interspecies relationships. Even trace concentrations of antibiotics can stimulate behavioral modifications, including diminished predator evasion, altered feeding strategies and decreased reproductive success in both fish and invertebrates.⁵⁴ Some studies have recorded that fluoroquinolones and macrolides can accumulate in aquatic arthropods such as insects and crustaceans. Those accumulations interfere with their moulting cycles and hormonal pathways. On the other side, they may affect the population dynamics and biodiversity and lead to changes in the community composition and the potential loss of ecologically significant species by reducing the capacity of ecosystems to hold up against concurrent stressors such as climate change and chemical pollution.⁴⁹ In addition to that, persistent occurrence of antibiotic residues in sediments serves as a chronic source of contamination as they slowly release active compounds and antibiotic resistance genes (ARGs) back into the aquatic environment and cause the disruption of sustaining ecological systems over extended periods.⁵⁵

Generally, the continual presence and persistent exposure of antibiotic residues in aquatic environments poses substantial risks to human health and ecosystem stability by facilitating the development and distribution of ARB, ARGs, while compromising the effectiveness of clinical treatments,⁴³ disrupting essential ecological processes and food web interactions and threatening biodiversity and functioning of aquatic ecosystems.⁵⁶ To lower these dangers, we need better monitoring, better treatment of wastewater and stricter rules about how antibiotics are used and thrown away.

3. Climate change and its influence on antibiotic contaminants

The accelerating pace of climate change is significantly altering the environmental systems worldwide. These changes cause complex challenges for the management of antibiotics like emerging contaminants. Antibiotic residues and ARGs have become prevalent pollutants in aquatic ecosystems due to the extensive use in human medicine, agriculture, and aquaculture. Alterations in environmental factors, including temperature, rainfall patterns and extreme weather events like floods and droughts, affect the behavior, distribution and environmental consequences of these antibiotic contaminants (Table 5).¹¹ A comprehensive knowledge of the relationship between climate change and antibiotic pollution and threats of antibiotic resistance is essential for the identification of future environmental risks, preservation of ecosystem health, protecting human populations and biodiversity conservation.⁵⁷

Table 5 Climate change impacts on antibiotic contamination and resistance

Climate change factor	Impact on antibiotics and ARGs	Ecological/human consequences	References
High temperature	Faster degradation of some antibiotics (β-lactams, tetracycline, macrolides, sulfonamides, fluoroquinolones), increased microbial activity and HGT of ARGs	Resistance proliferation, unstable treatment outcomes	5, 63, 64
Altered Rainfall & Storms	Surface runoff increases antibiotic load into aquatic systems	Peak pollution events increase antibiotic exposure to humans and the environment	11
Flood events	Infrastructure damage in treatment plants, contamination of drinking water and habitats	Increasing disease outbreaks, overwhelmed healthcare systems	11, 70
Drought	Increase antibiotic/ARG concentration, increase sediment toxicity	High toxicity to aquatic life and humans	11, 65, 66
Sediment remobilization	Increase bioavailability of sorbed antibiotics, HGT enhancement from resuspended ARGs	ARG cycling and ecological toxicity	66, 11
Microbial reorganization	Increase biofilm formation, increase ARB selection	Malfunctioning natural degradation pathways, ARGs persistence	67
GHG emissions from livestock	Climate acceleration, such as global warming and increased temperature	Reinforces the feedback loop between AMR and climate change	5, 68
WWTP sensitivity to climate	Reduce microbial efficacy, increase risk of effluent release during storms	Environmental dissemination of ARGs and antibiotics	11, 69, 70

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Climate changes affect the variations in temperature and hydrology. It directly affects the environmental fate and transport mechanisms of antibiotic contaminants. Elevated water temperatures can accelerate photodegradation and microbial breakdown of some antibiotic compounds and potentially reduce their environmental stability.⁵⁸ However, microbial activity is increasing under warmer climate conditions. This condition simultaneously facilitates the horizontal gene transfer and amplification of ARGs among microbial communities. As a result of that, resistance proliferation may be intensified.⁵⁹ Rising temperatures associated with climate change contribute to the proliferation of ARB across various ecosystems such as soil, glaciers, rivers and clinical settings.⁵ MacFadden, D. R., et al. found a positive correlation between temperature and antibiotic resistance rates in E. coli, Klebsiella pneumoniae, and Staphylococcus aureus by researching antibiotic resistance and temperature. It is recorded that a 10 °C increase in temperature was associated with a significant increase in resistance across several antibiotic classes.⁶⁰ Additionally, changing precipitation regimes, including more frequent and intense storms, enhance surface runoff from agricultural and urban areas. It increases the mobilization and entrance of antibiotics into aquatic environments.¹¹ These hydrological disturbances often result in periodic pollution peaks, complicating contamination monitoring and mitigation efforts. Therefore, climate-driven hydrological variability is a key factor that influences the concentration and ecological impacts of antibiotic residues in freshwater systems.¹¹ Singer and the research team reviewed antimicrobial resistance and its relevance to environmental regulators and reported that field and lab studies show rain events increase runoff from agricultural lands, transporting both antibiotic residues and ARGs into surface waters.⁶¹

Sediments act as important deposition sites for antibiotics and ARGs in aquatic ecosystems, and those contaminants can exist for extended periods.⁶² Climate change affects sediment dynamics and the remobilization potential of these pollutants due to the changes that occur in temperature regimes and water flow patterns. Warmer temperatures can improve the metabolism of the microbes that exist in sediment. It promotes the biodegradation of some antibiotics but also potentially increases the release of bound contaminants back into overlying waters.⁶³ Climate-related droughts reduce water levels and flow rates of the water bodies. It enhances the concentration of antibiotics and resistant bacteria within sediments and the water column. This increases the toxic effects on benthic and pelagic organisms.¹¹ Alterations in sediment oxygenation and redox conditions, which are driven by climate variability, further influence antibiotic sorption–desorption processes and affect their bioavailability and ecological toxicity.¹¹

Structure and functions of microbial consortia play an important role in facilitating antibiotic degradation and resistance gene dynamics. Climate change can alter the microbial diversity and activity by modifying factors such as temperature, nutrient availability and moisture conditions in the aquatic environment. These environmental changes may selectively favor ARB or improve the formation of biofilms, which serve as a pool for ARGs and facilitate their horizontal gene transfer.¹¹ Changes in microbial assemblages can undermine natural attenuation processes, allowing antibiotic residues and resistance determinants to persist and propagate within aquatic ecosystems.⁶⁴ Understanding and managing antibiotic pollution is challenging due to this ecological reorganization driven by climate stressors.

The relationship between climate change and antibiotic contamination causes threats to human health through the enhanced proliferation and spread of antibiotic-resistant pathogens (Fig. 4). The survival rates, replication and spread of resistant bacteria and pathogenic microbes in water bodies are increased due to the high temperatures and altered rainfall patterns.¹¹ Floods promote the migration of contaminated water into drinking supplies and recreational areas. That increases the human exposure risks. This collective interaction increases challenges faced by healthcare systems worldwide by boosting the spread of resistance genes and hindering infection control measures.¹¹ Therefore, climate change indirectly contributes to the difficult-to-treat infections occurring due to antimicrobial resistance and influences environmental reservoirs of resistant organisms.¹¹ Additionally, recent studies recognized that greenhouse gas emissions also contribute in the development of antibiotic resistance and infectious diseases.⁵ The use of antibiotics in livestock exacerbates climate change effects and leads to high methane emissions.⁶⁵

Fig. 4 Climate antibiotic resistance nexus: a systems interaction framework – source: created by the author using Microsoft PowerPoint.

Climate change also compromises the effectiveness of wastewater treatment infrastructures designed to reduce antibiotic contamination. Increased temperatures and fluctuating influent characteristics can impair microbial processes critical for the degradation of antibiotics and the removal of ARGs within treatment plants.¹¹ Additionally, storms and floods often damage or devastate treatment facilities and lead to the unexpected discharge of untreated or partially treated effluents into natural water bodies. This aggravates the release of antibiotics and resistance genes by extending their environmental persistence and ecological harm.¹¹ To address these compounded risks, it is essential to develop adaptive wastewater management strategies and climate-resilient infrastructure that is able to maintain treatment performance under variable climatic conditions.⁶⁶ Accordingly, recent studies highlight the need for integrated health and climate policies with collective evidence that suggests a complex interplay between climate change, antibiotic use, and the spread of resistant pathogens.⁶⁷

4. Conventional water treatment systems

4.1 Stages of conventional treatment methods and their limitations

Conventional water treatment methods are designed to remove physical, chemical and biological contaminants such as nutrients, biodegradable organic matter, pathogens, metals, and refractory organic compounds from raw water sources to produce safe and potable water. These methods are comprised of a series of established processes, including coagulation, flocculation, sedimentation, filtration and disinfection that target different types of impurities to ensure compliance with health standards (Fig. 5).^68,76 Recent studies highlight the advancements in coagulant formulations, enhancing performance for diverse water qualities. It causes effective removal of turbidity and particulate contaminants through coagulation and flocculation processes.^69,70 Further reduction of suspended solids and microbial load can be achieved by the sedimentation and filtration processes. Unfortunately, these methods, such as conventional sand filtration, may be limited in removing emerging micropollutants such as antibiotic residues.⁷⁰ The disinfection stage removes pathogenic microorganisms from water. Chlorination-like processes are involved in this stage as they continue to be critical barriers against pathogenic microorganisms, unless they may produce toxic byproducts and are not efficient in the complete removal of antibiotic residues and antibiotic resistance genes.⁷¹ Additional processes such as pH adjustment, aeration, and removal of specific contaminants such as iron, manganese may be implemented in treatment systems depending on the water source and quality goals. Activated carbon adsorption and coagulation, flocculation can also be used to target organic pollutants and taste-odor compounds. These conventional treatment steps target most of the traditional contaminants in water and provide safe water by removing those contaminants. Emerging pollutants such as antibiotics and antibiotic resistance genes create new challenges requiring advanced technologies because conventional methods are inefficient in completely removing those contaminants.⁴

Fig. 5 Conventional water treatment process flow diagram – source: created by the author using Canva elements (http://www.canva.com).

A study conducted in Sri Lanka recorded that treated water contains high concentrations of fluoroquinolones in 02 sewage treatment plants in Colombo and Hikkaduwa areas. The dominant antibiotic in the treated water was ciprofloxacin. Additionally, the presence of norfloxacin, trimethoprim, and erythromycin in treated water was detected.¹⁶⁸ However, these recent studies emphasise the necessity for integrating advanced treatment technologies with the conventional treatment methods to remove these emerging contaminants.⁷²

While these methods are effective on traditional contaminants, they often face challenges such as high operational costs and excessive sludge generation.⁷⁴ In order to achieve consistently high-quality finished water and maximize the process efficiency, conventional treatment plants should be optimised.⁷⁷ The selection of appropriate treatment methods should consider factors such as water quality, removal efficiencies and costs.⁷³

These conventional water treatment methods consist of several limitations, as most of them are designed to remove suspended solids and natural organic matter like macro contaminants instead of removing micro contaminants and emerging contaminants (Table 6).⁷ These methods often require high energy and chemical inputs, hindering their application in vulnerable regions with limited resources.⁹⁰ Additionally, conventional disinfection techniques like chlorination and UV treatment have shown drawbacks in controlling antibiotic-resistant bacteria and genes, necessitating the development of new sterilization methods.⁹⁰ Further, chlorination, like chemical disinfection methods, generates some harmful disinfection byproducts (DBPs) such as trihalomethanes and haloacetic acids. Those byproducts are linked to adverse health effects, including carcinogenicity and reproductive toxicity in humans.^7,90 Another significant drawback of conventional methods is the energy and chemical intensity of some processes. It can lead to high operational costs and increased environmental footprints. Moreover, the performance of conventional treatment can be reduced under variable water quality conditions, such as during extreme weather events that cause turbidity spikes or contamination influxes.⁹⁰ The inability to effectively degrade or remove viruses, protozoan cysts, and nano-sized particles using standard filtration methods also poses a public health concern.⁸³ Additionally, aging infrastructure in many treatment plants may lead to inefficient contaminant removal or secondary contamination during distribution.⁶⁶

Table 6 Stages, function, advantages and limitations of conventional treatment stages

Treatment stage	Function/purpose	Advantages	Limitations	Reference
Coagulation & Flocculation	Neutralize and agglomerate suspended particles into flocs using coagulants as aluminium sulfate (alum) or ferric chloride^77	- Effective in turbidity removal	- Inefficient for micro-contaminants (e.g., antibiotics)	78
			- Sensitive to water chemistry and temperature
		- Removes colloidal particles
		- Enhances sedimentation
Sedimentation	Settle and remove suspended solids via gravity	- Cost-effective	- Slower at low temperatures	78–81
			- Not effective for dissolved pollutants
		- Low energy consumption
			- Reduced efficiency during storm events
Filtration	Remove fine particles, microorganisms, and remaining solids using sand, gravel, and GAC	- Enhances microbial removal	- Cannot remove nano-sized or dissolved contaminants (e.g., ARGs, pharmaceuticals)	82–85
		- Dual-media and GAC filters improve efficiency
		- Basis for integrating nanomaterials
			- Membrane fouling issues in advanced systems
Disinfection	Kill or inactivate pathogenic microorganisms (chlorination, UV, ozone, etc.)	- Crucial for microbial safety	- May produce disinfection by-products (DBPs)	71, 86–89
			- Not effective for ARGs or antibiotic residues
		- Chlorination provides residual protection
			- UV/ozone requires high energy and maintenance
Additional steps (pH, aeration, etc.)	Adjust water chemistry and target specific contaminants (Fe, Mn, taste, odor)	- Enhances aesthetic and chemical quality	- Adds complexity and does not address emerging contaminants	4

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Because of these limitations, there is a growing requirement to integrate advanced treatment technologies such as membrane processes, advanced oxidation and biofiltration into existing systems to enhance contaminant removal efficiency and adaptability.⁹¹ Advanced techniques, including membrane filtration and electrocoagulation, have been developed to improve treatment efficiency, but they also have drawbacks such as membrane fouling and energy dependency.⁷⁵ Addressing these challenges is essential for ensuring long-term water quality and safety in the face of emerging pollutants and climate-induced stresses. The limitations of conventional treatments have spurred research into advanced alternative technologies, such as solar disinfection, which is recognized by the WHO as an appropriate method for producing safe drinking water in developing countries. As water quality threats evolve, there is an urgent need for more effective and efficient treatment technologies.⁶⁶

4.2 Impact of climate stressors on treatment efficiency

Conventional water treatment systems face significant and layered obstacles as climate changes affect operational stability and water quality assurance. Increased frequency and intensity of extreme weather events, including floods, storms, and droughts, are the major concerns because those events considerably change the characteristics of water. Elevated turbidity, suspended solids, nutrients and organic matter are introduced into water bodies by heavy rainfall and surface runoff during storm events.¹¹ Due to that, treatment processes get severely damaged and reduce their efficiency in the coagulation, sedimentation and filtration stages. Those conditions not only complicate process optimisation but also increase the risk of microbial and chemical contaminants bypassing treatment barriers and impact the safety of treated water.⁹²

Rising global temperatures further worsen these issues by influencing the biological and chemical dynamics of water treatment systems. Microbial communities in biological treatment units are affected by the increased ambient and water temperatures, which negatively impact microbial processes and hinder processes such as nitrification, denitrification and activated sludge performance.⁹³ And also, thermal stress may increase the growth of algae and cyanobacteria. They release toxins and organic precursors that form harmful DBPs during chlorination.¹¹ Additionally, increased rainfall intensity and variability cause hydraulic overloading in wastewater treatment plants, diminishing hydraulic retention time and treatment efficiency, especially in systems lacking real-time flow control or flexible process design.

These climate-induced stressors increase the operational costs, energy demands, and potential violations of regulatory water quality standards. Water utilities focus on implementing strategies to enhance system resilience and performance as a solution for these challenges. Those implementations include the coagulant and disinfectant adjustment, real-time monitoring, automation of operations and developing treatment infrastructure to accommodate fluctuating loads and contaminant profiles.⁹³ Membrane bioreactors and low-energy UV systems become prominent as sustainable solutions to mitigate the dual pressures of climate change and resource scarcity (Fig. 6).⁹⁴

Fig. 6 Climate change impacts on water treatment and adaptive responses – source: Created by the author using Canva elements (http://www.canva.com).

Additionally, a proactive and integrated planning framework that combines climate risk assessments, system redundancy, and flexible design principles is essential for long-term adaptation. Awareness of water treatment facilities can be enhanced by establishing capacity reserves, investing in modular treatment units, and integrating early warning systems for extreme weather events. As climate change continues to challenge the reliability of traditional water management approaches, the transition towards climate-resilient, adaptive and technology-driven treatment systems becomes essential to safeguarding public health and environmental sustainability.^9,66,93

5. Green nanotechnology: principles and materials

Nanotechnology has become apparent as a transformative field in the sectors of medicine, agriculture, electronics and environmental remediation due to its capacity to manipulate matter at the nanoscale. However, green nanotechnology is a branch that corresponds to nanoscience innovations with sustainability. Green nanotechnology emphasises the design and application of nanomaterials and nano-processes that are not only efficient but also environmentally benign and socially responsible throughout their life cycle.⁹⁵

5.1 Definition and principles of green nanotechnology

Green nanotechnology is the development of nanostructures and nanomaterials using eco-friendly methods. It focuses on minimal use of hazardous substances and a strong emphasis on resource efficiency, safety and sustainability.⁹⁶ It merges the core principles of green chemistry and green engineering for the design, synthesis, application and disposal of nanomaterials. This concept reduces environmental risks and enhances performance and functionality. This approach aims to create a sustainable nanotechnology platform by minimizing energy consumption, utilizing renewable resources, reducing waste, and promoting safe-by-design principles.^96,97

The main key principles that are used to derive green nanotechnology are based on green chemistry including the use of renewable resources, minimizing waste, employing non-toxic and biodegradable materials and designing for degradation rather than immortality. It also highlights energy efficiency, safe disposal, recycling and reuse of nanomaterials.⁹⁸ Additionally, it encourages the use of biological systems, such as plant extracts, bacteria, fungi, and enzymes, as reducing and capping agents for the synthesis of metal and metal oxide nanoparticles, which provides a more sustainable alternative to conventional chemical synthesis.⁹⁵ Some studies have synthesised Ag nanoparticles using neem (Azadirachta indica) extract, which exhibit potent antibiofilm and antimicrobial activity useful in water purification and medical applications.¹⁶⁰ Additionally, green tea extracts have demonstrated efficacy in the formation of Ag nanoparticles with antimicrobial properties.¹⁶²

Green nanotechnology marks a fundamental change from traditional nanofabrication techniques toward a more responsible and sustainable future.⁹⁹ It aims to reduce the ecological footprint of nanomaterial production and utilize the unique properties of nanomaterials for solving global challenges, including water purification, renewable energy, and targeted drug delivery.⁹⁸ At every stage of the nanomaterial life cycle, integration of environmental consciousness is essential to ensure that the benefits of nanotechnology do not come at the expense of ecological or human health.¹⁰⁰

Green nanomaterials and nanoproducts are produced by applying the above key principles of green chemistry and engineering. Those nanomaterials are environmentally safe and sustainable with minimal impact on human health.⁹⁸ The main intentions of the green nanotechnology concept are to minimize energy consumption, reduce waste and emissions and utilize renewable resources. The main features of green nanotechnology are environmental friendliness, cost-effectiveness and biocompatibility. Green nanotechnology takes a holistic approach, considering the full life cycle of nanomaterials to minimize unforeseen consequences.⁹⁶

The efficiency of nanomaterial production can be assessed using metrics like the E-factor, which varies widely across different synthesis methods. The E-factor is a green chemistry measurement used to quantitatively analyze the environmental impact of nanomaterial synthesis processes. It measures the ratio of waste to desired product. The higher values for E-factor indicate less efficient processes, while lower values indicate highly efficient processes.¹⁰¹ As an example, for gold nanoparticles, E-factors range from 102 to 105, which indicates significant variations in resource efficiency¹⁰¹ Some studies have demonstrated that lower E-factors suggest greener synthesis routes, as MoS₂–RGO nanocomposite catalyst with an E-factor of 0.089 for indole alkaloid synthesis.¹⁰²

The E-factor measurement is also useful in assessing solvent waste in pharmaceutical and fine chemical production. Micellar catalysis using designer surfactant nanoparticles in aqueous environments can drastically reduce E-factors by eliminating organic solvent waste.¹⁰³

In addition to the aforementioned principles of green chemistry and engineering, green nanotechnology includes the utilization of harmless solvents such as water or supercritical fluids, as well as the application of eco-friendly additives such as polysaccharides. Green synthesis of nanomaterials offers advantages compared to traditional physical and chemical methods, including eco-friendliness, cost-effectiveness, and biocompatibility.¹⁰⁴

5.2 Green synthesis approaches

Plant extracts those rich in phenolics, alkaloids, flavonoids, and terpenoids act as both reducing and capping agents in the green synthesis of metal nanoparticles.¹⁰⁵ As an example, Curcuma longa flower extract was used to synthesize silver nanoparticles (AgNPs), which are nearly 5 nm in diameter. These AgNPs contain antibacterial activity against E. coli and M. smegmatis, which is indicated by the inhibition zones of from 13 mm to 26 mm with minimum inhibitory concentration (MIC) values ranging from 6250 to 39 000 μg L⁻¹.¹⁰⁶ A recent study has demonstrated that coffee (Coffea arabica) leaf extracts indicate rapid AgNPs synthesis in approximately in 10 minutes with excellent stability and ultra-sensitive cysteine detection down to 0.1 nM.¹⁰⁷ Reviews indicate that AgNPs synthesised from plant extracts offer eco-friendly processing, flexible arrangement, and equivalent or enhanced antibacterial and catalytic performance relative to chemically synthesised alternatives.¹⁰⁴

Microorganisms such as bacteria, fungi, yeasts and microalgae serve as “nanofactories” through enzymatic reduction of metal ions. Bacillus subtilis is a prominent example which utilize agro-industrial waste, including sugarcane molasses, to biosynthesised AgNPs that are as small fragments with 4.8 nm diameter and 15.6 nm dynamic light scattering (DLS). Microbial extracellular synthesis can produce wide-ranging metal nanoparticles such as silver (Ag), gold (Au), and zinc oxide (ZnO) in a non-toxic and low-energy process.¹⁰⁸ Microorganisms secrete enzymes or reducing agents extracellularly and then reduce metal ions in solution to form nanoparticles using extracellular synthesis. It facilitates downstream recovery because it is easier to extract and purify the nanoparticles without breaking open cells, as in intracellular synthesis.¹⁰⁹

Agri-food by-products from fruit peels to crop residues provide a rich biodiversity of reducing agents and polysaccharides such as cellulose, lignin, and polyphenols. AgNPs and ZnO-NPs synthesised from agro-wastes like cocoa pods, aloe leaf, vegetable peels, and pomegranate husks have successfully indicated antibacterial activity against E. coli, S. aureus, and P. aeruginosa.^109,110,159 A study has used watermelon rind extract to synthesize AgNPs. Those AgNPs have been effectively used in food packaging materials, biomedical and cosmetic products.¹¹¹

Combining green-synthesised nanomaterials with other matrices enhances functionality. As an example, silver montmorillonite composites fabricated using Satureja hortensis extract have shown a broad spectrum of antibacterial properties.^112,113 A biodegradable food packaging material with superior antimicrobial efficacy has been synthesised by embedding ZnO nanoparticles (∼32–36 nm) extracted from neem leaf extract into starch biofilms.¹¹⁴ The green-synthesised films inhibited E. coli and S. aureus more effectively than their chemically synthesised counterparts, with inhibition zones of 14 mm versus 6 mm.^114,115

Recent international studies illustrate diverse global efforts to advance green nanomaterials for antibiotic and organic pollutant removal, revealing both strong performance and remaining challenges.¹¹⁵ In Finland, iron-modified peat and magnetite-pine bark biosorbents achieved maximum adsorption capacities of ∼200 mg g⁻¹ for levofloxacin and ∼153 mg g⁻¹ for trimethoprim, with real wastewater effluent removal efficiencies between 56.6–84.3% under a dosage of ∼3 × 10⁶ μg L⁻¹.²⁰⁰ A study in Thailand, ZnO nanoparticles extracted from green tea leaves (N-gZnO(w), ∼14.9 nm size, band gap ∼2.92 eV) removed over 96% of several pollutants, including ciprofloxacin under simulated sunlight, demonstrating both rapid kinetics and high efficiency.²⁰¹ In Egypt, a green nanocomposite ZnO@polyaniline/bentonite (Zn@PA/BE) under visible light showed significant photocatalytic oxidation of levofloxacin residues, which underscores the benefits of using hybrid supports to improve visible-light activity.²⁰² Additionally, in China, a GO/ZnO/Ag composite achieved ∼82.1% degradation of ciprofloxacin (20 mg L⁻¹ concentration, 15 mg catalyst dose, pH ∼5) under visible light, highlighting that doped composites can maintain high performance under non-UV light conditions.²⁰³

In another example, a rGO/nZVI composite synthesised via Atriplex halimus leaf extract achieved ∼94.6% removal of doxycycline under moderate conditions, including 25 mg L⁻¹ antibiotic, 25 °C, 0.05 g adsorbent, outperforming pristine nZVI (∼90%) and showing the synergistic effect of combining carbon support with nZVI.²⁰⁴

These diverse datasets in different regions worldwide reflect that green nanomaterials can deliver high removal efficiencies, but also indicate variability depending on pollutant type, synthesis method, support, light source, and environmental matrix.

5.3 Types of green nanomaterials used in water treatments

Green nanomaterials can be used in water treatment due to their properties such as biocompatibility, minimum toxicity and high efficiency in pollutant removal. Nanomaterials possess some unique physicochemical properties such as high surface area, tunable reactivity and high adsorptive properties. Thus, they are applicable for addressing a wide range of contaminants, including heavy metals, dyes, pharmaceuticals and microbial pathogens.¹¹⁶

Green-synthesised metal and metal oxide nanoparticles. Metal nanoparticles such as silver (AgNPs), iron oxide (Fe₃O₄), and zinc oxide (ZnO) synthesised using plant extracts, microbes, and agro-waste have been extensively investigated for water purification. Green-synthesised AgNPs have been utilized in filters due to their excellent antibacterial characteristics that suppress microbial growth.¹⁰⁸ Extracts from Moringa oleifera and Azadirachta indica have been used to synthesize ZnO nanoparticles, which exhibit significant photocatalytic degradation of dyes such as methylene blue and rhodamine B when exposed to sunlight.^117,118 Magnetite-like iron oxide nanoparticles are distinctly effective in the removal of heavy metals such as arsenic, chromium and fluoride from drinking water, and magnetic separation can be used for the recovery.¹¹⁹ A study has reported the green synthesis of CuO nanoparticles by using eco-friendly and non-toxic Phyllanthus amarus leaf extract. These synthesised CuO nanoparticles were in monoclinic phase with an average particle size of 20 nm and possessed antibacterial activity against various multidrug-resistant bacteria, including both Gram-positive (B. subtilis and S. aureus) and Gram-negative (E. coli and P. aeruginosa). The highest antibacterial activity has been shown against B. subtilis.¹⁶⁰ Some studies have proven that green ZnO NPs contain more enhanced biocidal activity against various pathogens compared to chemical ZnO NPs.¹⁶¹

Green-synthesised AgNPs exhibit potent antimicrobial properties, effectively degrading dyes and inactivating pathogens. Their high reactivity and broad-spectrum efficacy make them suitable for diverse applications. However, concerns arise regarding their potential ecotoxicity, bioaccumulation, and the risk of promoting antibiotic resistance gene transfer in microbial communities. These issues necessitate careful consideration of their environmental impact and long-term sustainability.¹⁹⁴

Green-synthesised ZnO NPs offer photocatalytic activity under UV light, enabling the degradation of organic pollutants. Their effectiveness is enhanced under specific conditions, such as UV irradiation. Nevertheless, their limited photocatalytic efficiency under visible light and potential toxicity to aquatic organisms pose challenges to their widespread application.¹⁹⁶

TiO₂ NPs are favored for their high stability, low toxicity, and effectiveness in photocatalytic degradation processes. They are particularly advantageous in environments with abundant UV light. However, their requirement for UV activation and the potential formation of reactive oxygen species leading to secondary pollution highlight the need for further optimisation to enhance their applicability under diverse environmental conditions.¹⁹⁷

Biopolymer-based nanomaterials. Cellulose, chitosan, alginate and starch are the most prominent biopolymers that are used to synthesize nanomaterials with different sorption capacities. Nanocellulose can be derived from agro-waste or bacterial sources, possesses a high surface area and mechanical stability. Hence, these nanocellulose are suitable for heavy metal adsorption and membrane fabrication.¹²⁰ Chitosan-based nanomaterials, generally cross-linked or bonded with metal nanoparticles, demonstrate efficacy against negatively charged contaminants because of the presence of amino groups.¹²¹ Additionally, alginate-based nanobeads loaded with green-synthesised iron oxide or silver nanoparticles have been successfully tested for the removal of pathogens and heavy metals in real water matrices.¹²²

Chitosan-based nanomaterials are biodegradable and exhibit low toxicity. They serve as effective adsorbents for heavy metals and other pollutants, offering an eco-friendly alternative to synthetic materials. Despite their advantages, limitations such as limited reusability and the necessity for chemical modifications to enhance performance must be addressed to improve their practicality in large-scale applications.¹⁹⁸

Carbon-based green nanomaterials. The use of green synthesised biochar and graphene derivatives is more frequently observed in water treatment applications.¹²³ Biochar nanoparticles derived from agro-waste via pyrolysis or hydrothermal carbonization possess large surface areas, tunable porosity, and functional groups that favor the adsorption of antibiotics, pesticides, and dyes.^124,125 Green-reduced graphene oxide (rGO) synthesised using plant polyphenols or microbial reductants, exhibits high affinity toward aromatic pollutants and can act as a supporting material for photocatalysts. The characteristic of visible light-driven photocatalytic degradation of organic contaminants can be improved by integrating rGO-based composites with TiO₂ or ZnO.¹²³ A study has demonstrated that GO materials are active and affect pollutants in wastewater by direct interaction or by affecting the biological processes of activated sludge.¹⁵⁸

Graphene oxide (GO) and reduced graphene oxide (rGO) nanomaterials can be functionalized for specific contaminants, enhancing their versatility in wastewater treatment. However, the high production costs and potential environmental impact if not properly disposed of raise concerns regarding their economic feasibility and sustainability.¹⁹⁹

Nano-clays and hybrid nanocomposites. In water purification, nano-clays such as montmorillonite, bentonite and kaolinite are commonly used as an eco-friendly solution. They possess unique characteristics such as a layered structure, ion-exchange properties and large surface area. The affinity for heavy metals and dyes gets improved with the modification of nano-clays with natural extracts or polymers.¹²⁶ Green synthesised nanoparticles are integrated with biopolymers or carbon compounds in order to produce hybrid nanocomposites. In some studies, they have demonstrated synergistic effects which lead to superior performance in pollutant removal, reusability, and environmental safety.¹²⁷ A study has demonstrated the effective removal of heavy metals, including cadmium, chromium and lead in wastewater using green-synthesised clay–polymer nano-composite of M. oleifera seed and bentonite clay.¹⁶¹

Green-synthesised nanomaterials provide innovative and sustainable ways to address current challenges in water purification (Table 7). Future research should focus on optimizing synthesis processes, lifecycle assessment and combining these nanomaterials into modular, low-cost treatment systems for widespread application in both urban and rural circumstances.¹²⁸

Table 7 Summary of green-synthesized nanomaterials for water purification

Nanomaterial type	Source/precursor	Target contaminants	Key mechanism	Reference
AgNPs	Azadirachta indica leaf extract	E. coli, pathogens	Antimicrobial action	117
ZnO NPs	Moringa oleifera	Dyes – methylene blue (MB), rhodamine B (RhB)	Photocatalytic degradation	118
Fe3O4 NPs	Tridax procumbens	Arsenic, fluoride	Adsorption & magnetic recovery	149
Nanocellulose	Sugarcane bagasse	Pb^2+, Cd^2+	Adsorption	108, 120
Chitosan–AgNP	Shrimp shell & green AgNPs	Pathogens, dyes	Sorption & disinfection	120, 121
Alginate–Fe3O4 beads	Sodium alginate & Fe3O4	Fluoride, pathogens	Ion exchange & antimicrobial	122
Biochar NPs	Rice husk pyrolysis	Ciprofloxacin, tetracycline	Adsorption	123–125
rGO–ZnO composite	C. sinensis extract	RhB, antibiotics	Photocatalysis & adsorption	123, 160
Montmorillonite–neem clay	Clay & Azadirachta extract	Pb^2+, microbes	Ion exchange & antimicrobial	113
Chitosan–Ag–biochar	Agro-waste based	Heavy metals, pathogens	Hybrid synergy	121

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Strengths and weaknesses of nanomaterials used in water treatment. When considering the materials like zero-valent metal nanoparticles excel in reducing power and contaminant degradation, but their instability, including oxidation and aggregation, recovery challenges and toxicity limit real-world deployment. Metal oxides and photocatalysts share this pattern as they are good in controlled settings, but performance suffers when light conditions, water composition, or reuse demands increase.²⁰⁸ Carbon-based materials and nanocomposites can offer very high adsorption capacity and multifunctionality, but high cost of production, scale challenges, and complex synthesis pathways are frequent limitations.²⁰⁸ Nanocomposites improve functions but at the cost of more potential failure points and higher fabrication difficulty.²⁰⁸ The potential of combining strengths of adsorption, catalytic performance and recovery is clear as seen in the nanocomposites, but achieving those synergies without incurring high cost, synthesis complexity, or trade-offs is nontrivial.²⁰⁸ Recovery of almost all nanomaterials leads to regenerate them without large losses in performance, and ensuring low environmental toxicity is major hurdles.²⁰⁸ Membranes and nanofiber systems help with continuous flow and separation, but suffer from fouling, durability, and energy or maintenance demands.²⁰⁹

Many strengths mentioned in Table 8 derive from lab or model-water experiments, but when exposed to real waters, environmental conditions, and long-term operations, weaknesses often dominate. Thus, researchers should pay more attention to durability, regeneration, cost-effectiveness, and life-cycle environmental risk in future research.

Table 8 Comparison of nanomaterial types: strengths vs. weaknesses for water treatment

Type of nanomaterial	Strengths	Weaknesses	Reference
Zero-valent metal nanoparticles (nZVI, nZn, nAl, etc.)	– Very strong reducing ability	– Prone to oxidation	208
		– Aggregation
	– Useful for the degradation of redox-labile contaminants	– Difficulty in recovery/separation
		– Possible toxicity due to the release of metal ions
		– Stability issues in real water matrices
	– Good adsorption and precipitation for heavy metals
	– Relatively inexpensive (e.g. iron)
Metal oxide nanoparticles (TiO 2 , ZnO, Fe oxides, etc.)	– Useful photocatalytic properties	– Many require UV light or specific wavelengths	208
	– Good adsorption	– Expensive
	– Fe oxides are sometimes magnetic for easier recovery	– Photo-corrosion (e.g. some ZnO)
	– Versatile, depending on functionalization or composite formation	– Limited light absorption spectrum
		– Possibility of low efficiency under real conditions
		– Issues in separation/reuse
Carbon-based materials (CNTs, graphene, graphene oxide, etc.)	– Very high specific surface area	– High cost of production	208
		– Sometimes difficulty in large-scale manufacture
	– Strong adsorption capacity
		– Issues with dispersibility (aggregation), stability
	– Good for organic contaminants, dyes, and sometimes heavy metals
		– Possible toxicity/environmental persistence
		– Difficulty in regeneration/reuse
		– Potential clogging or fouling (in membranes)
	– Possibility of functionalization for selectivity
	– Can be used in composite systems
Nanocomposites (metal/metal oxide/carbon hybrids, magnetic composites, etc.)	– Can combine thebenefits of multiple materials (e.g. adsorption + photocatalysis + magnetic recoverability)	– More complex synthesis	208
		– Highly expensive
		– Potential for more points of failure
	– Enhanced efficiency due to synergistic effects	– Stability of the composite
		– Sometimes the parts interfere (e.g. light absorption blocked by certain components)
	– Can tailor properties to specific contaminants
		– Recovery and reuse remain challenging
	– Better separation if magnetic parts are included
		– Risk of leaching of dangerous components
Membrane-based nanomaterials/nanofiber/nanofiltration membranes	– Physically exclude many contaminants	– Membrane fouling	209
		– Durability (mechanical, chemical)
	– Tunable pore sizes
		– Possible release of nanomaterials if not firmly embedded
		– Cost of high-quality membranes
	– Provide continuous flow systems
		– Energy requirements
		– Regeneration/cleaning issues
		– Scale-up/lifespan concerns
	– When modified with nanomaterials, membranes may gain antimicrobial or anti-fouling properties
	– Useful for separation processes like desalination, micro/ultrafiltration etc.

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5.4 Mechanisms of antibiotics removal using nanomaterials

Nanomaterials are highly effective in the removal of antibiotic residues like emerging contaminants from the aquatic environment because they exhibit extraordinary physicochemical properties, such as high surface area, tunable porosity and unique surface chemistry. Adsorption, photocatalytic degradation, membrane filtration and redox reactions are the most common mechanisms by which nanomaterials remove antibiotics from contaminated water (Fig. 7 and Table 9).¹²⁹

Fig. 7 Mechanisms of nanomaterial-based antibiotic removal from water – source: Created by the author using Microsoft PowerPoint.

Table 9 Mechanistic overview of nanomaterials in eliminating antibiotic contaminants

Mechanism	Nanomaterials used	Efficiency/performance	Optimal conditions	Advantages	Limitations/considerations
Adsorption	CNTs, GO, biochar-based nanocomposites	High adsorption capacity for tetracyclines, sulfonamides	Modified with –COOH/–OH groups; ambient temperature; neutral pH	Simple process, reusable, no light required	Efficiency decreases in extreme pH/salinity; saturation limits capacity^123,129–131
Photocatalytic degradation	TiO2, ZnO, g-C3N4, TiO2/graphene composites	Complete degradation of ciprofloxacin within 60 min (TiO2/graphene)	UV/visible light exposure; aqueous solution; ambient to slightly elevated temperatures	Rapid degradation; mineralization of antibiotics; no sludge generation	Requires a light source; recombination of electron–hole pairs reduces efficiency without modification^132–134
Membrane filtration	Ag NP or GO-embedded membranes	High rejection (>90%) for pharmaceuticals	Neutral pH; moderate salinity; low to medium pressure	Anti-fouling, selective removal, easy integration into existing systems	Fouling still possible; membrane replacement/maintenance required^135,136
Redox-based transformations	nZVI, Fe3O4 nanoparticles	Effective reductive inactivation of nitroimidazoles and quinolones	Neutral to slightly alkaline pH; presence of a reducing environment	Dechlorination and nitro reduction; can treat complex contaminants	Sensitive to oxygen; particle aggregation; possible secondary iron precipitation^137
Combined/hybrid approaches	Combinations of the above nanomaterials	Enhanced removal efficiency and reduced secondary pollution	Optimised for target contaminant, pH, temperature, and salinity	Synergistic mechanisms improve robustness and adaptability	Requires careful design and operational control; higher material cost^138

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Nanomaterials such as carbon nanotubes (CNTs), graphene oxide (GO), and biochar-based nanocomposites use the adsorption mechanism.¹²³ These materials possess interactions including π–π electron donor–acceptor interactions, hydrogen bonding and electrostatic attraction between the nanomaterial surface and antibiotic molecules.¹³⁰ These interactions lead to high adsorption capabilities in those nanomaterials. Some studies have demonstrated that multi-walled CNTs possess enhanced adsorption of tetracycline when they are modified with –COOH and –OH groups because hydrogen bonding and electrostatic interactions are improved.¹³¹

Photocatalytic degradation is the second most common mechanism applied with nanomaterials. This mechanism is mostly employed with TiO₂, ZnO, and g-C₃N₄ like nanomaterials, which possess semiconductive properties. They produce reactive oxygen species (ROS) such as hydroxyl radicals (·OH) and superoxide anions (O₂·⁻), and break down antibiotic molecules into safer or mineralized end products once exposed to UV or visible light.¹³² As an example, when exposed to visible light, complete degradation of ciprofloxacin can be achieved within 60 minutes using TiO₂/graphene composites because of increased electron mobility and lowered recombination rates.^132–134

A further mechanism is membrane filtration with nanomaterial-embedded membranes. Fouling is one of the major obstacles that occur during membrane filtration. As an alternative to this issue, membranes with silver nanoparticles or GO layers have demonstrated inhibited biofouling with properties such as antibiotic removal through size exclusion, surface adsorption and antimicrobial activity. These nano membranes possess characteristics such as high sulfamethoxazole and amoxicillin rejection rates, good permeability and fouling resistance.^135,136

In addition to that, zero-valent metal nanoparticles such as nanoscale zero-valent iron (nZVI) and metal oxides, such as Fe₃O₄, use redox-based transformations as the mechanism in environmental remediation and hazardous waste treatment. This mechanism has demonstrated reductive inactivation of nitroimidazoles and quinolone antibiotics. The electron transfer that cleaves chemical bonds in antibiotic compounds can be amplified by the redox potential of these nanomaterials, facilitating dechlorination and the reduction of nitro groups in water treatment.¹³⁷

Both the efficiency of antibiotic removal and reduced secondary pollution can be enhanced by combining these mechanisms. In the real world, it is critical to enhance the removal processes due to the selection of nanomaterials, functionalization strategies and operational parameters.¹³⁸

5.5 Performance under climate-influenced conditions

Climate change affects the environmental parameters, including temperature, precipitation, pH, salinity and contaminated profiles. These changes directly impact the stability, reactivity and efficiency of green synthesised nanoparticles.¹³⁹ Plant extracts, microbes or agro waste-based green nanomaterials possess superior functional properties. Unfortunately, their behavior under vibrant environmental conditions is a crucial factor to consider.¹⁰⁴

Temperature is a main factor that affects the rate of pollutant degradation and the stability of nanoparticles. For instance, TiO₂ nanoparticles synthesised from Moringa oleifera leaf extract have demonstrated enhanced photocatalytic degradation of methylene blue dye at high temperatures (45 °C) due to enhanced mobility of ROS and high light absorption.¹⁴⁰ And also, thermolabile organic capping agents synthesised using plant extracts degrade due to persistent heat and lead to nanoparticle agglomeration and suppressed reactivity.¹⁴¹ While elevated temperatures can enhance certain catalytic reactions, such as improving the photocatalytic activity of TiO₂, they can simultaneously induce adverse structural changes in biogenic or plant-derived nanomaterials. This contrasting behavior underscores the need to explore strategies that can balance temperature-driven performance enhancement with stability preservation.¹⁷⁵ Recent studies have highlighted the importance of optimizing material design to mitigate the detrimental effects of temperature on nanomaterial stability. For instance, the incorporation of thermally stable supports and surface functionalization techniques can enhance the structural integrity of nanomaterials under varying temperature conditions.¹⁷⁵ Additionally, the development of hybrid composites and the use of protective coatings have shown promise in maintaining the performance and longevity of nanomaterials exposed to thermal stress.¹⁷⁶

Surface functionalization and nanoscale scaffolding in nanocellulose-based systems have proven highly effective in mitigating instability while preserving catalytic functionality. For instance, cellulose nanocrystals (CNCs) modified with polydopamine enabled in situ generation and anchoring of silver nanoparticles have successfully demonstrated a significantly enhanced colloidal stability by preventing aggregation, a boosted antibacterial catalytic activity more than 4-fold compared to unanchored AgNPs.²³⁶ In another study, CNC/CTAB (hexadecyl-trimethylammonium-bromide) was used as a support for AgNPs, and the resulting CNC–CTAB–Ag composite showed not only a narrower size distribution of silver nanoparticles but also a higher rate constant in the catalytic reduction of 4-nitrophenol than unsupported Ag NPs, due to better dispersion and immobilization of the active species.²³⁷ By exploiting the abundant surface hydroxyl groups of CNCs, silver ions were electrostatically bound and reduced to form AgNPs without added surfactants, yielding a highly stable catalytic system with minimal leaching during reactions.²³⁸

Composite engineering with nanocellulose further enhances thermal robustness and reusability under challenging conditions. A study reported that a nanocellulose/Fe₃O₄/Ag nanocomposite displayed peroxidase-mimetic activity even up to 65 °C, retaining structural integrity thanks to the strong anchoring of Ag and Fe₃O₄ on the cellulose scaffold.²³⁹ Similarly, in cellulose nanofiber (CNF) supports decorated with noble metal nanoparticles (Au, Ag, Ni), the high surface area and hydrogen-bonding network of CNFs prevented rapid nanoparticle agglomeration, enabling rapid (within ∼5 min) and efficient reduction of 4-nitrophenol even at low loadings.²⁴⁰ Moreover, the thermal stability and degradation behavior of functionalized nanocellulose are strongly influenced by metal loading. For instance, incorporation of Ag or Au nanoparticles into sulfonated cellulose nanofibers lowered the onset of thermal decomposition compared to bare nanocellulose, but the hierarchical network preserved enough stability to maintain nano-catalyst performance.²⁴¹

Acid rains and eutrophication cause pH fluctuations, which lead to influence the surface charge and aggregation behavior of nanoparticles. Green silver nanoparticles synthesised using Camellia sinensis extract exhibited excellent antimicrobial activity at neutral pH but suffered a 35% drop in performance in acidic media (pH 4), primarily due to particle aggregation and altered surface ionization.^142,143 Similarly, iron oxide nanoparticles synthesised from Eucalyptus globulus extract possess a significant adsorption capacity for arsenic(V) in slightly acidic to neutral pH, while their efficacy diminishes in very alkaline circumstances due to the repulsion between negatively charged surfaces and anionic species.¹⁴⁴

In coastal and estuarine environments, salinity is a critical factor that affects the nanoparticles. A study demonstrated a 20–30% decrease in dye degradation performance of green-synthesised ZnO nanoparticles in 3% NaCl (saline water). This may occur due to the ionic shielding effects that affect charge transfer mechanisms. It underscores the production of salt-resistant green nanomaterials.¹⁴⁵

During storms and flooding adsorption capacity of nanoparticles gets affected as they have to compete for active sites due to organic matter loading. At high levels of humus-derived substances (20 000 μg L⁻¹), green iron oxide nanoparticles produced from Psidium guajava leaf extract have shown a 40% reduction in phosphate removal efficiency. Steric hindrance and competitive binding may be the main causes for this instance. However, the particles have the potential to be reused as they have shown performance recovery after mild regeneration.¹⁴⁶

In addition to that, UV radiation exposure positively influences the photocatalytic performance of green nanomaterials. As an example, TiO₂ nanoparticles synthesised from Ocimum sanctum extract have shown more than 95% degradation of tetracycline under modelled solar radiation in less than 90 minutes. This result highlights the capability for solar-assisted wastewater remediation in sunny climates.¹⁴⁷

For instance, silica nanoparticles modified with zwitterionic and hydrophilic silanes retained colloidal stability and adsorption capacity for over one month in 3.5% NaCl brine at 60 °C, indicating robust tolerance to high salinity and thermal stress.¹⁷¹ In contrast, unmodified silica nanofluids exhibited rapid aggregation and loss of stability at elevated ionic strengths (42 × 10⁶ μg L⁻¹ NaCl) and 80 °C, unless stabilized by surface modification or pH adjustment.¹⁷³ Similarly, a g-C₃N₄/La–N–TiO₂ nanocomposite achieved complete ciprofloxacin degradation (∼5000 μg L⁻¹) within 60 minutes under simulated sunlight at pH 6.5, with only minor inhibition in the presence of common ions such as Na⁺, Ca²⁺, and Mg²⁺, though nitrate ions (NO₃⁻) significantly suppressed the degradation rate.¹⁷⁴ These examples underscore that nanomaterial functionality is highly sensitive to climatic and environmental variability, especially ionic composition, salinity, and temperature and that surface functionalization and compositional engineering play decisive roles in maintaining efficiency under stress. Incorporating such empirical evidence into the design and evaluation of climate-resilient nanomaterials is therefore essential to ensure consistent antibiotic removal performance in dynamic real-world water systems.

However, it is essential to study heat stability, pH tolerance, salinity resistance of nanoparticles and competition from organic matter when applying them in water treatment under climate-impacted conditions (Table 10).

Table 10 Impact of climate stressors on green nanomaterial performance

Climate stressor	Nanomaterial type	Effect on performance	Mechanistic insight	Reference
Temperature increase	Silver nanoparticles (AgNPs)	Enhanced antimicrobial activity	Elevated temperatures can accelerate the release of silver ions, increasing antimicrobial efficacy	205
pH fluctuations	Titanium dioxide (TiO2) nanoparticles	Altered photocatalytic efficiency	pH changes affect the surface charge and band gap of TiO2, influencing its photocatalytic activity	206
Extreme weather events (e.g., flooding)	Carbon nananotubes (CNTs)	Potential aggregation and reduced adsorption capacity	High flow rates can lead to the dispersion or aggregation of CNTs, reducing their surface area and adsorption efficiency	207
Salinity increase	Graphene oxide (GO) nanocomposites	Enhanced pollutant removal	Increased salinity can improve the stability and dispersion of GO, enhancing its adsorption properties	207
Heavy metal contamination	Iron oxide nanoparticles (Fe3O4)	Increased removal efficiency	Presence of heavy metals can promote the formation of reactive oxygen species, aiding in pollutant degradation	207

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6. Case studies, recent developments and research gap

6.1 Main practical applications of green-synthesised nanoparticles applied for antibiotic remediation

Green synthesised nanoparticles support the antibiotic remediation because they are eco-friendly, cost-effective and highly efficient in antibiotic removal (Table 11). Ag, Fe₃O₄, ZnO, and TiO₂, like metal and metal oxide nanoparticles derived from plant extracts, bacteria, fungi, and agro-waste, have the potential to remove antibiotics through adsorption, photocatalysis, and redox reaction mechanisms. As an example, Ag nanoparticles synthesised from Azadirachta indica extract have demonstrated high antibacterial and degradation efficiency opposed to tetracycline and ciprofloxacin via combined oxidative and membrane-disruption mechanisms.¹¹⁷ Similarly, ZnO nanoparticles produced using Moringa oleifera demonstrated 85–90% degradation of sulfamethoxazole under UV light in less than 120 minutes, facilitated by reactive oxygen species generation.¹¹⁸ Moreover, iron oxide nanoparticles derived from Psidium guajava have been employed successfully to adsorb fluoroquinolones, with Langmuir isotherm models confirming monolayer adsorption and high surface affinity.¹⁴⁶ These applications point to the strong potential of green nanomaterials for targeted antibiotic mitigation in wastewater treatment and environmental remediation.

Table 11 Comparative efficiency of green-synthesised nanomaterials for antibiotic degradation

Nanomaterial	Antibiotic targeted	Degradation efficiency	Kinetic model	Efficiency under different climate changes
CuO NPs	Rifampicin	High	Pseudo-second-order	Exhibits improved degradation efficiency compared to conventional methods^186
Fe 3 O 4 NPs	Rifampicin	High	Pseudo-second-order	Demonstrates high efficiency under varying pH and temperature conditions^187
ZnO NSs	Ciprofloxacin	∼90% within 2 hours	Pseudo-first-order	Shows excellent photocatalytic activity under sunlight^188
NiFe 2 O 4 /CeO 2 /GO NC	Tetracycline	95% in 90 minutes	Not specified	Exhibits high photocatalytic activity under visible light^189

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6.2 Field trials and laboratory-scale studies

In current literature, laboratory-scale studies on green-synthesised nanomaterials and their use in water remediation are dominant, while pilot-scale and semi-field applications are explored widely. A recent study conducted in rural India has incorporated biosynthesised TiO₂ nanoparticles into filtration units for household-level greywater. These nanoparticles have successfully reduced more than 70% of tetracycline and amoxicillin concentrations under natural sunlight.^133,148 And also, controlled experimental trials conducted in constructed wetlands using Fe₃O₄ NPs have demonstrated sulfamethoxazole and trimethoprim removal up to 80% without affecting aquatic plants or microbial activity.¹⁴⁹

A study reported that a pilot-scale industrial wastewater treatment system was developed using Eichhornia crassipes (water hyacinth) biomass modified with ethylenediaminetetraacetic acid (EDTA) to treat approximately 80 litres of Cr(VI)-contaminated water. The system demonstrated effective chromium removal, with a cost-effective setup priced around USD 10, showcasing the potential for low-cost, sustainable treatment options.¹⁹⁰ Another study conducted to synthesize magnetite-based magnetic nanofibers (MNFs) via electrospinning reported the application of a pilot-scale setup to degrade tetracycline in pig manure wastewater. That study revealed that the MNFs exhibited high stability and catalytic efficiency, with treatment efficiency increasing with hydrogen peroxide concentration up to an optimum point, offering a scalable solution for antibiotic-contaminated wastewater.¹⁹¹ A pilot-scale study evaluated the use of a coagulant extracted from Cassia fistula seeds for treating real domestic textile wastewater. The coagulant has achieved a 93.83% removal of pollutants, demonstrating its potential as an effective, natural coagulant in wastewater treatment.¹⁹²

Recent studies have highlighted the importance of considering cost factors, such as the price of raw materials and energy consumption, when scaling up nanomaterial-based water treatment systems. For instance, the synthesis of titania nanoparticles, a common material in water treatment, can cost between $16 per kg, which is significantly higher than conventional methods.¹⁸⁴ Addressing these cost challenges is crucial for the widespread adoption of nanotechnology in water treatment.

Nanomaterial loss during long-term operation can significantly impact the efficiency and sustainability of water treatment systems. Studies have explored various regeneration strategies to mitigate this issue. For example, electrostatic regeneration of functionalized adsorbents has been demonstrated as an effective method for removing nitrates from water, with up to 40% of the initial adsorption capacity being recoverable.¹⁸⁵ Implementing such regeneration techniques can enhance the longevity and cost-effectiveness of nanomaterial-based water treatment systems.

In spite of these findings, consistency under environmental and water chemistry conditions is challenging. Laboratory conditions often idealize parameters such as pH, temperature, and contaminant concentration, which do not always reflect real wastewater matrices.

6.3 Comparative efficiency with conventional methods

Green synthesised nanoparticles possess superior performance to conventional materials and methods, including activated carbon, ozonation and photocatalysis in the removal of antibiotic contaminants in water. As an example, instead of traditional adsorption methods, iron oxide nanoparticles produced from plant extracts have shown over 90% efficiency in the removal of tetracycline and ciprofloxacin.¹⁵⁰ Generally, Ag nanoparticles synthesised from Azadirachta indica extracts contain bactericidal and antibiotic degradation capacities with lower toxicity and lesser energy input compared to chemically synthesised other variants.¹¹⁷ Chlorination, UV degradation and like conventional methods generally require high energy input and toxic reagents. Green NPs are comparatively sustainable solutions in order to minimize the impact of those factors. In a comparative study, bio-synthesised ZnO NPs removed sulfamethoxazole from aqueous solution more efficiently than UV photolysis alone, with minimal sludge generation and no harmful by-products. Nevertheless, the synthesis method, pH, size and contaminant type affect the efficiency of green NPs. Thus, it highlights the optimisation of those parameters.¹⁵¹

6.4 Limited studies on combined climate-antibiotic-nanotechnology interactions

Despite growing interest in nanotechnology for environmental remediation, few studies have explored the triadic interaction between climate change, antibiotic contaminants, and nanomaterials (Table 12).¹⁵² Both behavior and fate of antibiotics and nanomaterials in the aquatic environment can be altered due to climate change. As an example, high temperatures and fluctuating pH impact the efficacy and transportation of NPs due to changes in nanoparticle stability and reactivity. Meanwhile, the antibiotic load in natural systems get increased by the rainfall-driven overflow and wastewater burden due to climate effects.¹⁵³ The current lack of research in this nexus limits the ability to predict performance and risks under future environmental scenarios. As an example, increased temperatures may enhance nanoparticle degradation rates or aggregation. And also, changes in redox potential due to flooding or drought cause modifications in the chemical speciation of both antibiotics and nanoparticles. Hence, integration of climate-resilience and the design of green nanomaterials is a critical, underexplored, research frontier.¹⁵⁴

Table 12 Climate change, antibiotic contamination and nanotechnology interactions in water treatment: Current insights and research gaps

Interaction aspect	Current status	Research gaps	Proposed research directions	References
Climate Change & Nanomaterial Stability	High temperatures and fluctuating pH can affect nanoparticle stability and reactivity, potentially altering their efficacy in water treatment	Limited studies on how climate stressors influence nanomaterial degradation and aggregation	Conduct controlled laboratory experiments to assess the impact of temperature, pH, and UV radiation on nanomaterial stability and performance	212
Climate Change & Antibiotic Contaminants	Climate effects, such as increased rainfall and flooding, can elevate antibiotic loads in natural water systems, exacerbating contamination levels	Insufficient data on the combined effects of climate change and antibiotic contamination on water quality	Implement long-term monitoring programs in ecosystems experiencing diverse climate stressors to track antibiotic concentrations and their environmental impacts	11
Nanomaterials & Antibiotic Degradation	Nanomaterials have shown potential in degrading antibiotic contaminants through mechanisms like photocatalysis and adsorption	Variability in nanomaterial performance under different environmental conditions	Investigate the effectiveness of various nanomaterials in degrading antibiotics under simulated climate stressors to identify optimal materials and conditions	210
Integrated climate-antibiotic-nanotechnology Nexus	The interplay between climate change, antibiotic contaminants, and nanomaterials is complex and not well understood	Lack of comprehensive studies integrating all three factors	Develop predictive models that incorporate climate variables, antibiotic concentrations, and nanomaterial behaviors to forecast treatment efficacy and risks under future environmental scenarios	211

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Conducting controlled laboratory experiments to assess how climate stressors, including temperature, pH, and UV radiation, influence the degradation efficiency of nanomaterials in antibiotic-contaminated water will help identify optimal conditions and potential limitations of nanomaterial performance under varying environmental stressors. Implementation of long-term monitoring programs in ecosystems experiencing diverse climate stressors, such as coastal wetlands or urban rivers, with regular sampling and analysis will provide real-world data on antibiotic concentrations, nanomaterial presence, and microbial community composition, facilitating the development of predictive models for nanomaterial performance in natural settings. Utilizing advanced techniques like transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) to examine structural and chemical changes in nanomaterials exposed to simulated climate stressors will enhance our understanding of nanomaterial stability and reactivity in dynamic environmental conditions.

By integrating these approaches, future research can elucidate the complex interactions between climate change, antibiotics, and nanomaterials, informing the design of climate-resilient nanomaterials for effective environmental remediation.

6.5 Need for long-term environmental impact assessments

Green synthesis is accepted as eco-friendly. However, assessments of long-term environmental impact are insufficient. Most studies focus on acute toxicity or short-term removal efficiency, with limited understanding of nanoparticle persistence, bioaccumulation, and ecosystem effects. As an example, even though plant-based AgNPs are synthesised from plant extracts, they may produce ionic silver over time, which can pose risks to aquatic species and microbial ecosystems.¹⁵⁵ Ecological trade-offs of installing green NPs at scale should be adequately analyzed using chronic exposure studies and life-cycle assessments (LCAs).¹⁵⁵ Incorporating ecotoxicological endpoints including effects on microbial diversity or antibiotic resistance gene propagation, is essential for thorough risk evaluation. Without such assessments, the large-scale application of green nanomaterials may accidentally introduce new environmental challenges.¹⁵⁶

A study reported that a comprehensive LCA was conducted to evaluate the environmental impacts of a green-synthesised nanomaterial-based adsorbent developed for cadmium (Cd²⁺) removal from wastewater. This study compared the impacts associated with the production, use, and recycling phases of the adsorbent. The findings revealed that the synthesis phase contributed significantly to the overall environmental footprint, primarily due to the energy-intensive processes involved. However, the use phase demonstrated substantial environmental benefits, with the adsorbent effectively removing Cd²⁺ ions from contaminated water, thereby reducing the need for chemical treatments. The recycling phase showed potential for minimizing environmental impacts, provided that efficient regeneration methods were employed. This case study underscores the importance of considering the entire life cycle of nanomaterials to assess their true environmental sustainability.¹⁸⁰

For instance, a comparative LCA of TiO₂ nanoparticles synthesised via green chemistry versus traditional methods highlighted the reduced environmental footprint of the green synthesis route, emphasizing its potential for sustainable production.¹⁸² However, it is important to note that many LCA studies have been limited to early life-cycle stages, with limited data on end-of-life impacts.¹⁸³

Comprehensive LCA studies are crucial to evaluate the environmental impacts of green nanomaterials throughout their life cycle, from raw material extraction to end-of-life disposal. These analyses can identify potential environmental hotspots and inform strategies to mitigate negative impacts.¹⁷⁹Table 13 provides a concise comparison of ecotoxicity data and cradle-to-gate life-cycle assessment (LCA) metrics for common green nanomaterials.

Table 13 Ecotoxicity and LCA for green nanomaterials

Nanomaterial class	Ecotoxicity	Key Ecotoxicity metrics	Life-cycle assessment (LCA) findings	LCA metrics/impacts	References
Cellulose nanomaterials (e.g., CNC, CNF)	Low direct acute lethal toxicity, but can interact with other NPs to modulate toxicity	Nanocellulose enhances the dispersion and toxicity of ZnO NPs toward green algae Eremosphaera viridis	LCA of different production routes (e.g., enzymatic, no-pretreatment, carboxymethylation) shows a large variation in environmental impact	Some studies reported that the no-pretreatment route (homogenization) vs. carboxymethylation route had very different energy demands. Also, LCRA (life cycle risk assessment) screening-level hazard assessment finds limited cytotoxicity/inflammation for second-generation cellulose materials, indicating favorable hazard profile	220–222
Silver nanoparticles (AgNPs) (green-synthesized)	High to moderate aquatic toxicity, strongly dependent on coating, dissolution	Classic LCA study shows upstream silver extraction dominates environmental burden. Also, synthesis and disposal of nano-silver in textiles strongly influence ecotoxicity	Comparative LCA (cradle-to-gate) of 7 AgNP synthesis routes (including bio-based/green) shows large differences, bio-based reduction trades off lower energy vs. increased ozone depletion or ecotoxicity potential	Up to > 90% of the life-cycle burdens come from silver metal production (not nanoparticle synthesis) in some routes	223, 224
				In textile LCA, for 1 kg AgNPs, green synthesis is not always lower-impact e.g., modified Tollens' method nearly produces 580 kg CO2-eq. per kg
Titanium dioxide (TiO 2 ) nanoparticles (green-synthesized)	Moderate ecotoxicity, relatively lower than silver, but size/coating matters	LC50 data for fish: in Oreochromis mossambicus (96 h) reported nearly 165 mg L^−1	LCA comparing green biosynthesis (e.g., plant-extract route) vs. traditional chloride route: green route reduces some impact, but energy-intensive steps (e.g., calcination) remain significant	According to LCA, calcination and centrifugation stages dominate CO2 emissions; the green route can reduce hazardous by-products	182
Iron oxide nanoparticles (FexO y ), green-synthesized	Some toxic effects on aquatic invertebrates and cyanobacteria	For example, chronic exposure of Biomphalaria glabrata (snail) to gluconic acid-functionalized IONPs (1.0–15.6 mg L^−1) resulted in bioaccumulation, morphological changes. Also, Nostoc ellipsosporum (cyanobacteria) exposed to FeO NPs (0–100 mg L^−1) showed cytotoxic effects	Cradle-to-gate LCA (green vs. coprecipitation method) using Cymbopogon citratus extract: green-synthesized IONPs have much lower normalized total environmental impact vs. conventional	In the green-synthesized route, the marine aquatic ecotoxicity indicator was 7.6 × 10^−10 (normalized), compared to 1.22 × 10^−8 for the coprecipitation route	225–227
Chitosan-based nanoparticles (e.g., chitosan NPs, silver–chitosan composite)	Variable toxicity, chitosan alone is less toxic, but composites can be very toxic	LC50 for zebrafish larvae exposed to chitosan (CS) nanoparticles was nearly 28.9 mg L^−1 (without ascorbic acid (AA)), 57.4 mg L^−1 (with AA)	Chitosan is a biopolymer derived from chitin, so generally favorable in resource depletion, specific LCA studies are scarce/underdeveloped	Because detailed cradle-to-gate LCA is sparse, one critical research gap is here	228, 229
				The environmental trade-offs of chitosan NP production (e.g., energy, sourcing) are not yet well characterized in LCA literature
		For silver–chitosan composites: 48 h EC50 (Daphnia magna) = 0.065–0.232 mg L^−1; 24 h LC50 (Thamnocephalus platyurus) = 0.25–1.04 mg L^−1

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7. Environmental risks, challenges and future perspective

Application of green synthesised NPs in the removal of antibiotic residues in water has acquired public recognition. However, before large-scale implementation, it is essential to address several environmental and technical risks.¹⁵⁷ A key concern is the uncertain ecotoxicity of green NPs in natural ecosystems. Although, green NPs are safer than chemically synthesised alternatives, they can trigger oxidative stress, interfere with microorganisms and bioaccumulate in aquatic organisms. As an example, plant-based AgNPs have shown antimicrobial effects that may unintentionally harm beneficial microorganisms and aquatic biodiversity.¹⁰⁹ Studies have shown that AgNPs, commonly used for their antimicrobial properties, can be toxic to aquatic organisms. For instance, exposure to AgNPs has been linked to oxidative stress and genotoxicity in fish and algae.¹⁰⁹ ZnO NPs have demonstrated cytotoxic effects on various aquatic species, including algae and crustaceans. Chronic exposure can lead to bioaccumulation and adverse ecological impacts.¹⁹³ While TiO₂ NPs are generally considered less toxic, long-term exposure studies indicate potential risks to aquatic ecosystems, including alterations in microbial communities and sediment-dwelling organisms.¹⁹⁴

Some studies on high-rate algae ponds (HRAPs) have revealed that microalgae can bioaccumulate pharmaceuticals and their metabolites from wastewater, suggesting that green nanomaterials could similarly accumulate in biota, potentially entering the food chain.¹⁹⁵ Recent studies indicate that nanoparticles can settle in sediments, where they may be taken up by benthic organisms, leading to long-term ecological consequences.¹⁹⁴

The use of antimicrobial nanomaterials like AgNPs may exert selective pressure on microbial communities, potentially promoting the proliferation of antibiotic-resistant genes. This underscores the need for comprehensive studies on the impact of nanomaterials on microbial resistance dynamics.¹⁹⁴

7.1 Scalability challenges in implementing green nanomaterials for water treatment

While pilot-scale studies and economic estimates strengthen the promise of green nanomaterials, their practical deployment in water treatment systems is impeded by several critical scalability issues, such as synthesis reproducibility, energy and cost demands, long-term stability in realistic water matrices, regeneration and reuse, integration with existing infrastructure, regulatory and environmental risk concerns, etc. Nanomaterials synthesis reproducibility remains a major issue because green routes often rely on biological or plant-derived reducing agents, which vary in composition from batch to batch, leading to inconsistencies in nanomaterial size, surface chemistry, and performance.^160,177,230 Additionally, laboratory syntheses often produce only small quantities, leading to variability among batches and making it difficult the scale up processes.²³¹ Without tight process control, such variability undermines both efficacy and quality assurance. The heterogeneity of bio-based feedstocks including plant extracts and biomass, further complicates standardization. Continuous-flow synthesis (e.g., microreactors) has been proposed to improve throughput and reproducibility by recycling solvents and maintaining more controlled reaction conditions.²³¹

Green synthesis offers benefits for the energy and cost demands of scaled-up production. For instance, in nanocellulose production, drying, homogenization, continuous mechanical fibrillation or thermal steps in nanoparticle calcination are energy-intensive, which leads to increased capital and operational costs. Green-synthesized nanomaterials must therefore balance eco-friendliness with economic viability.^232,233 In chitosan-based nanocomposites, in situ sol–gel or thermal methods may limit upscaling due to the cost of high-purity chitosan and process energy.²³⁴ The cost-effectiveness of green synthesis methods is a significant concern. While these methods may reduce the need for hazardous chemicals and energy-intensive processes, they can involve higher raw material costs or longer production times. Economic analyses are necessary to compare the total cost of green synthesis with conventional methods, considering factors like raw material availability, process time, and waste management. Studies have evaluated and compared the cost-efficiency of green versus traditional methods, focusing on factors such as material cost, energy consumption, yield, and compliance costs.¹⁷⁸ Emerging synthesis methods, such as microwave-assisted and sonochemical synthesis, have demonstrated high scalability from laboratory to industrial scale, with production costs for certain nanomaterials falling below €10 per kg.¹⁸¹ These advancements suggest that green nanotechnologies can be economically viable for large-scale applications.

Green nanomaterials can be destabilized due to aggregation, loss of surface charge, or decreased activity by the variable pH, high ionic strength, dissolved organic matter and competing ions in the natural and industrial waters.²³⁵ This instability may reduce treatment efficiency and shorten the usable life of the nanomaterial, making it a critical challenge for long-term stability in realistic water matrices.²³⁵ For chitosan-mediated nanoparticles, leaching and aggregation over repeated cycles under varying pH have been reported.²³⁴

Protocols for regeneration and reuse are not always well developed for green nanomaterials. Repeated cycles of adsorption–desorption or catalytic regeneration can lead to structural damage, loss of active sites, or irreversible aggregation, all of which compromise long-term performance. The absence of robust, scalable regeneration strategies threatens the cost-effectiveness and sustainability of these materials. Integrating life cycle assessment (LCA), safe-by-design synthesis, and predictive modelling is therefore essential to mitigate potential risks. For example, chitosan/Fe₃O₄ systems lose 20–40% of adsorption capacity after several cycles due to aggregation.²³⁴

Additionally, integration with existing infrastructure is non-trivial. Conventional water treatment systems may not accommodate free nanoparticles, requiring immobilization strategies including membrane embedding, magnetic separation, etc., to prevent nanoparticle losses, clogging, or pressure-drop issues.²³⁵ Scaling such hybrid systems involves complex engineering trade-offs.

Regulatory and environmental risk concerns remain underaddressed. Even green-synthesized nanomaterials raise questions about long-term ecotoxicity, potential nanoparticle release, and lifecycle environmental impacts. Comprehensive risk assessment frameworks and standardization are essential to enable safe, large-scale deployment.²³²

The lack of standardized protocols and environmental risk assessments further complicates regulatory oversight and public safety. Synthesis of nanomaterials from a collection of biogenic NPs with biochar, cellulose nanofibers like functional supports, may lead to higher stability, reusability and efficient removal of contaminants. However, lab-scale innovation should be converted into sustainable water treatment technologies by incorporating interdisciplinary approaches that are linked with climate resilience, socio-economic feasibility and circular economy.¹⁰⁵

LCA studies for green nanomaterials are currently limited and need to be expanded to provide a holistic understanding of their environmental footprint. Recent reviews have discussed the application of LCA in assessing the environmental impacts of nanomaterials and have highlighted the need for more comprehensive studies to evaluate the sustainability of green synthesis methods.¹⁷⁹

Addressing these challenges through interdisciplinary research and collaboration among academia, industry, and regulatory authorities will be critical to advancing the safe and scalable commercialization of green nanotechnology for sustainable water treatment.

8. Conclusion

Green synthesized NPs address the issue of water contamination due to emerging contaminants including antibiotics, through current ongoing research and have shown successful results for the challenges. Their unique characteristics, such as low-cost synthesis, biocompatibility, multifunctionality, high adsorptive capacities, and applicability across diverse water treatment scenarios, make these NPs a better alternative compared to conventional water treatment methods. To realize the potential of this, future research should focus on climate-integrated wastewater treatment plants, long-term field validation, harmonized ecotoxicity assessments and multi-dimensional evaluations including life cycle impacts, regulatory compliance, and socio-environmental safety while embedding safe-by-design principles in nanoparticle development to ensure efficacy under real-world conditions. Laboratory studies have consistently demonstrated their superior removal efficiencies, yet practical implementation remains constrained by knowledge gaps in environmental impact, performance under varying climatic conditions, and long-term toxicity. Case studies highlight promising results but also underscore the need for standardized methodologies and holistic impact assessments. Additionally, fostering interdisciplinary collaboration with climate scientists and translating scientific evidence into policy guidelines and integrated water management strategies will accelerate sustainable implementation. By addressing these gaps, green nanomaterials can drive innovative, scalable, policy-compliant and resilient solutions for antibiotic pollution control and global water sustainability.

Author contributions

Nawagamuwage Harshani Madushika: investigation, writing – original draft. Imalka Munaweera: conceptualization, writing, review, and editing, supervision. Gayani Yasodara Liyanage: conceptualization, writing, review, and editing, supervision. Pradeepa Jayawardane: conceptualization, writing, review, and editing, supervision. Pathmalal Manage: conceptualization, writing, review, and editing, supervision.

Conflicts of interest

The authors declare that there is no conflict of interest.

Data availability

As a review paper, this manuscript does not generate any new or original data. All data and information presented herein were obtained from previously published studies, which were cited and referenced within the manuscript.

Acknowledgements

Financial support for this study is acknowledged by the National Research Council, Sri Lanka under the research grant number IDG 24-023.

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