Bio-Based Composites of Alginate, Cellulose, and Moringa Oleifera for Heavy Metal Removal in Water Purification: A Comprehensive Review of Mechanisms, Fabrication, and Performance

Abstract

The escalating prevalence of heavy metal contamination in aquatic ecosystems, driven by industrialisation, urbanisation, and population growth, has necessitated the development of sustainable and efficient water purification technologies.Although widely adopted, conventional treatment approaches, including chemical precipitation, ion exchange, and membrane filtration, are often limited by high operational costs, secondary pollution, and limited efficacy in treating mixed or low-concentration contaminants. In response to these limitations, biopolymerbased adsorbents have emerged as promising alternatives due to their biodegradability, low toxicity, and high density of functional groups. This review critically evaluates recent advances in developing and applying bio-based composites comprising sodium alginate, cellulose, and Moringa oleifera to remove heavy metals from aqueous systems. The review examines the physicochemical characteristics, adsorption mechanisms, and synergistic properties of these biopolymers, emphasising the role of the active compounds in each. The incorporation of Moringa oleifera seed extracts, rich in cationic proteins and bioactive compounds, is discussed in the context of its dual functionality as a natural biosorbent. This review identifies potential applications, highlights key research gaps, and outlines future directions for advancing biobased composite materials as viable solutions for sustainable water treatment.HighlightsI.Alginate, Cellulose, and Moringa oleifera composite systems exhibit synergistic binding interactions with heavy metal ions.II.Electrostatic attraction, ion exchange, and surface complexation govern metal-biopolymer interactions.III.Moringa oleifera introduces bifunctional groups enhancing metal ion affinity in hybrid biopolymer matrices.IV.Hydroxyl and carboxyl groups in alginate and cellulose facilitate coordinated multi-site adsorption.