Waste biomass based sodium lignosulfonate/chitosan/polyvinyl alcohol/polyacrylic acid hydrogel for the synergistic adsorption of Levofloxacin and Cu2+ with copper recovery.

Antibiotic and heavy metal contamination in livestock wastewater poses escalating environmental challenges, while conventional adsorption methods are hindered by low efficiency, poor reusability, and potential secondary pollution. In this study, a sustainable sodium lignosulfonate/chitosan/polyvinyl alcohol/poly(acrylic acid) (SLS/CS/PVA/PAA) hydrogel was synthesized by free-radical polymerization using chitosan that had been functionally enhanced with sodium lignosulfonate. The experimental results showed that the hydrogel exhibited high adsorption capacities for levofloxacin (LEV) and Cu2+, reaching 1146.73 mg·g-1 and 70.6 mg·g-1, respectively. The adsorption mechanisms were elucidated through kinetic and isothermal models, fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS). The density functional theory (DFT) calculations reveal that the key binding sites involve -OH and -NH2 groups of CS and -COOH and -SO3H groups. Synergistic interactions between LEV and Cu2+, including ion bridging and complexation, significantly enhanced LEV removal. The molecular dynamics simulation confirm that Cu2+ modulates surface charge via -SO3- binding and enhances LEV adsorption through ionic bridging. Moreover, copper recovery was achieved by combustion with a recovery rate of 77.31 ± 1.3 %. This study offers a green and cost-effective strategy for pollutant removal and metal recovery, highlighting the potential of SLS-functionalized chitosan hydrogels in environmental remediation.