Adsorption/desorption performance of Pb²⁺ and Cd²⁺ with super adsorption capacity of PASP/CMS hydrogel

Super-absorbent polyaspartic acid/carboxymethyl Salix psammophila powder (PASP/CMS) hydrogel was prepared by aqueous solution polymerization. PASP/CMS hydrogel was characterized by Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results showed that PASP/CMS hydrogel is prepared by graft copolymerization of the -COOH of polyaspartic acid (PASP) and the -CH₂OH of CMS. The surface of the hydrogel became dense from loose porosity, and Pb²⁺ and Cd²⁺ were adsorbed onto the surface of hydrogel. The crystallinity of CMS was destroyed by the addition of PASP. The initial concentration of Pb²⁺ and Cd²⁺, pH, adsorption time and adsorption temperature on the adsorption effect were studied through experiments. Results showed that hydrogel has a good removal effect on Pb(II) and Cd(II) ions. Pseudo-second-order kinetics and Langmuir isotherm models are represented in the process, which are spontaneous, exothermic and decreased in randomness, and it is a single layer chemical adsorption. At the same time, the effect of desorption experimental parameters (HNO₃ initial concentration, desorption time, and desorption temperature) on the experiment was studied and optimized.