Abstract
Using Pearson’s hard and soft acids and bases (HSAB) principle as the design guideline, a novel chitosan/poly(ethylene glycol)/poly(acrylic acid) (CS/PEG/PAA) hydrogel adsorbent containing hard Lewis base adsorption site (i.e., amino group, hydroxyl group, ether linkage, carboxylate ions) was prepared by glow-discharge electrolysis plasma (GDEP) technique and then applied for the selective adsorption of Pb2+. A copolymerization mechanism initiated by GDEP was proposed. The structure, thermal stability, and morphology of CS/PEG/PAA adsorbent were characterized by FT-IR, thermogravimetry/differential thermogravimetry (TG/DTG), and SEM. The effects of the solution pH and contact time on the single-component adsorption were examined by batch experiments. Competitive adsorptions of Pb2+ and Cd2+ were carried out under equal mass concentration and equal molar concentration. In addition, regeneration and reusability of adsorbent were also investigated in detail. The results showed that the maximum adsorption capacities for Pb2+ and Cd2+ are 431.7 and 265.0 mg g−1, respectively. The kinetic behaviors of the adsorption and the fourth desorption for single component and the competitive adsorption for Pb2+ follow the pseudo-second-order model with pH = 4.8. The CS/PEG/PAA adsorbent has good adsorption selectivity for Pb2+ with the coexistence of Cd2+. The adsorbent displays excellent regeneration and reusability in the EDTA-4Na solution.
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