Modified Corn Straw Hydrogel Adsorbent Fabricated via Embedding for Removing Cu2+ and Pb2+ from Wastewater

In this study, a modified corn straw hydrogel adsorbent (CSHA) was fabricated via the embedding method. The adsorbent facilitates phase separation after adsorbing lead ions (Pb2+) and copper ions (Cu2+) from wastewater. A set of experiments verified that metal ions formed coordination bonds with the carboxyl functional groups on the adsorbent surface. The influences of pH, contact time, initial metal ion concentration and temperature on adsorption performance were systematically explored. The results revealed that the adsorption capacities for Cu2+ and Pb2+ were 396.43 mg/g and 151.96 mg/g, respectively, under the given experimental conditions. The adsorption process followed the pseudo-second-order kinetic model and the Langmuir isotherm model. The thermodynamic calculations indicated that the adsorption was an endothermic and spontaneous process accompanied by increased system disorder. After five adsorption–desorption cycles, the removal efficiency of CSHA remained above 65%. This work offers a low-cost, eco-friendly and high-performance adsorbent for heavy-metal-containing wastewater treatment.