Competitive Adsorption Removal of Heavy Metals From Aqueous Solutions Using Ecofriendly Sodium Alginate/Sulfhydryl‐Modified Chitosan@ZIF‐8 Gel Beads

ABSTRACT In this study, halloysite@polydopamine/chitosan/sodium alginate@ZIF‐8 (HNTs@PDA/CS/SA@ZIF‐8) gel beads were prepared via in situ growth technology for the competitive adsorption of Cd 2+ + Ni 2+ from aqueous solutions. The gel beads were characterized by FT‐IR, SEM, BET and XPS. Through batch experiments, the effects of pH, initial concentration, and adsorption time were evaluated. Adsorption kinetics studies revealed that adsorption followed a pseudo‐second‐order kinetic model. The isothermal adsorption conformed to the modified competitive Langmuir (MCL) isotherm model. The maximum adsorption capacities of Cd 2+ +Ni 2+ were 262.90 mg/g and 107.01 mg/g, respectively. Regeneration experiments indicated that the gel beads maintained 88% and 96% of their initial adsorption capacities for Cd 2+ and Ni 2+ , respectively, after four adsorption/desorption cycles. The DFT calculations indicated that the gel beads had the highest uptake and selectivity for Cd 2+ over Ni 2+ due to better chemical affinity. The adsorption mechanism was attributed mainly to chelation coordination and electrostatic interactions. The results proved that HNTs@PDA/CS/SA@ZIF‐8 had excellent adsorption capacity, were environmentally friendly, and exhibited vast potential in wastewater treatment applications.