Novel Zwitterionic Inorganic−Organic Hybrids: Kinetic and Equilibrium Model Studies on Pb2+Removal from Aqueous Solution

Pb 2+ removal from aqueous solution using zwitterionic hybrid polymers as adsorbents was studied. Influence factors such as solution temperature, initial pH, adsorption time, and solution concentration on Pb 2+ adsorption were investigated. Adsorption kinetics data were modeled using four two-parameter kinetic equations (i.e., Lagergren first-order and second-order, Ritchie modified second-order, and intraparticle diffusion models). It was indicated that Pb 2+ adsorption on these zwitterionic hybrid polymers followed the Lagergren second-order kinetic model. Meanwhile, the equilibrium adsorption data were analyzed using four two-parameter isotherm equations (i.e., Langmuir, Freundlich, Dubinin−Radushkevich, and Temkin isotherm models). The results reveal that the adsorption of Pb 2+ ions followed the Langmuir isotherm model. The thermodynamic parameters Δ G, Δ H, and Δ S for Pb 2+ removal from aqueous solution were also calculated. The negative values of Δ G and the positive values of Δ H are evidence that Pb 2+ adsorption on these zwitterionic hybrid polymers is spontaneous and an endothermic process in nature. Moreover, the zwitterionic hybrid polymers produced reveal relatively high desorption efficiency in 1.0 mol·dm −3 aqueous HNO 3 solution, indicating that they can be recycled in industrial processes. These findings suggest that the zwitterionic hybrid polymers are promising adsorbents for Pb 2+ removal from contaminated water.