Removal of Pb²⁺ from wastewater using composite microspheres based on chitosan crosslinked with aminated silica

The emission of hazardous lead (Pb²⁺) from industrial effluents presents significant environmental and public health risks, necessitating the creation of effective and sustainable remediation materials. This study generated chitosan-aminated silica (C-ASi) composite microspheres via covalent crosslinking with sebacoyl chloride to improve the adsorption efficiency and structural integrity of chitosan. Adding aminated silica to the microspheres boosted their specific surface area to 134.54 m²/g, which is over 200 times more than that of pure chitosan. It also added a lot of amino functional sites for Pb²⁺ binding. The best C-ASi-3 microspheres could hold up to 80.5 mg/g of Pb²⁺ and could still remove more than 80 % of it even when other ions (Zn²⁺, Ca²⁺) were present. Adsorption kinetics and isotherm studies demonstrated that Pb²⁺ uptake conformed to a pseudo-second-order and Langmuir model, signifying monolayer chemisorption mostly governed by coordination between Pb²⁺ and amino groups. FTIR and XPS tests also showed that amide linkages and coordination connections had formed between Pb²⁺ and nitrogen and oxygen atoms on the surface. Regeneration testing demonstrated that the materials were reusable, with HCl rapidly eliminating them and EDTA maintaining their stability over an extended period. The findings indicate that the amalgamation of organic chitosan with inorganic aminated silica enhances adsorption efficacy synergistically. This study presents a simple, cost-effective, and sustainable method for the creation of hybrid bioinorganic adsorbents with considerable potential for heavy metal wastewater treatment.