Cu (II) removal from aqueous solution and real textile wastewater: mechanistic insights, process optimization, and theoretical modeling using advanced Chitosan–EDTA beads

Abstract

Copper ions (Cu2⁺) are highly toxic and persistent pollutants in industrial wastewater, posing serious environmental and health risks. This study develops a sustainable chelating adsorbent based on ethylenediaminetetraacetic acid-functionalized chitosan beads (Chitosan@EDTA) for efficient Cu2⁺ removal from aqueous solutions and real textile wastewater. The material was designed by integrating EDTA chelation chemistry with chitosan bead structure. Characterization analyses confirmed successful EDTA grafting and the formation of a mesoporous network with a surface area of 8.81 m2/g and an average pore diameter of 3.19 nm, promoting ion diffusion. Batch adsorption experiments showed a high Langmuir monolayer adsorption capacity of 184.16 mg/g at pH 5 (R2 = 0.990), outperforming several conventional adsorbents. Thermodynamic analysis indicated that the adsorption process was spontaneous, endothermic, and entropy-driven. Response Surface Methodology based on Box–Behnken Design was applied to optimize operational parameters and obtain a highly accurate predictive model (R2 = 0.9996). Density Functional Theory analysis revealed enhanced chemisorption through coordination interactions between Cu2⁺ and amine and carboxylate groups, supported by reduced HOMO–LUMO energy gaps. Practical application demonstrated 98.2% Cu2⁺ removal from real textile wastewater. Overall, Chitosan@EDTA shows strong potential as an efficient and sustainable adsorbent for industrial wastewater treatment.