Cu2+, Cd2+, and Pb2+ ions adsorption from wastewater using polysaccharide hydrogels made of oxidized carboxymethyl cellulose and chitosan grafted with catechol groups

Heavy metal pollution is a global environmental threat that jeopardizes both human health and ecosystems. To combat this issue, the adsorption method has emerged as a cost-effective, efficient, and environmentally friendly solution. Hydrogels, three-dimensional hydrophilic polymer networks, display remarkable swelling and adsorption capabilities, making them superior to other adsorbents. They facilitate easier adsorbate transfer, resulting in enhanced adsorption efficiency. This study introduces a novel, energy-efficient approach for crafting metal-ion hydrogel adsorbents. The process involved grafting catechol groups onto chitosan (CS-CH) and then forming a hydrogel through a Schiff base reaction between CS-CH and oxidized carboxymethyl cellulose (OCMC). Successful hydrogel formation was confirmed using FTIR and UV–Vis spectroscopies. The hydrogel’s dual interaction mechanism, facilitated by catechol and amine groups, enhanced its pollutant-binding capacity. Under optimal conditions (pH = 7) and a 180-min adsorption period, the OCMC/CS-CH hydrogels exhibited significant practical adsorption efficiencies: 89.6% for Cu 2+ , 80.5% for Cd 2+ , and 91.8% for Pb 2+ ions. Subsequent experiments reaffirmed its exceptional adsorption performance for these ions. Notably, the hydrogel maintained its efficacy even after five cycles of adsorption and desorption in 0.1 mol/L HCl, showcasing its impressive regeneration potential. Collectively, the straightforward fabrication process, consistent performance, and negligible secondary pollution make this hydrogel a promising candidate for a wide array of applications in addressing heavy metal contamination. Graphical abstract