Green removal and waste valorization of ciprofloxacin from water using zinc–iron LDH–chia seed biocomposites: integrated adsorption, computational modeling, and electrochemical conversion

Abstract

The contamination of water with pharmaceuticals like ciprofloxacin (CFX) presents serious environmental challenges, necessitating efficient and sustainable treatment methods. This study introduces a novel green adsorbent based on zinc–iron layered double hydroxides (Zn–Fe LDH) encapsulated with chia seed mucilage for effective CFX removal. The synthesized Zn–Fe LDH/chia seed composite demonstrated exceptional efficacy, achieving 98.5% removal of CFX from water at pH 8. The adsorption process was best described by the Langmuir model, revealing a remarkably high maximum capacity of 850.05 mg g⁻¹. Thermodynamic studies confirmed the process was spontaneous and exothermic. The composite exhibited excellent regenerability, retaining 85.2% of its initial adsorption capacity after five consecutive cycles using a simple 0.1 M NaOH eluent. The composite proved to be cost-effective, with a synthesis cost of $2.033 per gram. Quantum chemical modeling revealed strong interactions (ΔE_int = −32.5 kcal mol⁻¹) between CFX and the chia-modified LDH surface, validating the experimental results. Furthermore, the material exhibited excellent potential for waste valorization, showing current densities of 18.71 mA cm⁻² and 15.45 mA cm⁻² for methanol electro-oxidation before and after adsorption, respectively. A semi-pilot filtration system successfully demonstrated practical scalability, achieving >80% CFX removal from raw wastewater within 20 minutes. Greenness assessment tools (AGREEprep, BAGI, RGB12) confirmed the eco-friendly nature of the entire process, supporting circular economy goals through this low-cost, dual-function material design.