Adsorption performance of polysaccharide-based hydrogel SCAS for heavy metal ions

Polysaccharide-based hydrogel SCAS was synthesized from cornstarch （St） and sodium carboxymethyl cellulose （CMC-Na） as raw materials, acrylamide （AM）, acrylic acis （AA） and 2-acrylamido-2-methylpropane sulfonic acid （AMPS） as graft monomers. Another polysride-based hydrogel StAS was synthesized from St by using the same graft monomers. Two kinds of hydrogels were used to adsorb Cu²⁺ in solution, and their adsorption performances were compared. Due to the addition of CMC-Na, the adsorption performance of SCAS was superior to that of StAS. The adsorption kinetics and adsorption isotherm data of the two hydrogels were fitted, and the results showed that the adsorption process of Cu²⁺ on the two hydrogels was consistent with Langmuir model and quasi-second-order kinetic model, which belonged to monolayer adsorption and chemical adsorption. At 25 ℃, the adsorption capacity of StAS was 85.47 mg·g⁻¹, while that of SCAS was 99.90 mg·g⁻¹. Using SCAS as a Cu²⁺ adsorbent, it was suitable for water quality conditions with 4.0<pH<5.5. When the solution contained high valence cations （Fe³⁺）, the adsorption effect was significantly reduced. When several heavy metal ions were present simultaneously in the solution, SCAS selectively adsorbed the heavy metal ions in the order of Cu²⁺>Cd²⁺>Ni²⁺. Research on the adsorption mechanism showed that the adsorption of Cu²⁺ by SCAS was mainly through coordination. SCAS had good recyclability, and after 4 regenerations, the Cu²⁺ removal rate could still reach 83.2%. The research results provide ideas and references for the research and development of polysaccharide-based hydrogels.