Selective adsorption of lead(II) from aqueous solution by ion-imprinted PEI-functionalized silica sorbent: studies on equilibrium isotherm, kinetics, and thermodynamics

摘要

A new ion-imprinted poly(ethyleneimine)(PEI)-functionalized silica sorbents were synthesized by a hydrothermal-assisted surface grafting technique with Pb(II) as the template, PEI as the functional molecular, and epichlorohydrin as the cross-linking agent for the selective adsorption of Pb(II) from aqueous solution, and was characterized by FTIR, SEM, TGA-DTA, nitrogen adsorption, and the static batch experiment. Static adsorption experiment results showed that Pb(II)-imprinted PEI-functionalized silica sorbents had high static adsorption capacity of 60.4mgg(-1), reached an equilibrium state within 20min, displayed stable adsorption ability for Pb(II) ions in the range of pH 4-8, had satisfactory selectivity toward Pb(II) and could be used repeatedly. Compared with Freundlich and Dubinin-Radushkevich isotherms, equilibrium data fitted to Langmuir adsorption model. The kinetic process of adsorption followed a pseudo-second-order model compared to pseudo-first-order, Elovich and intraparticle diffusion models. Negative values of G degrees indicated spontaneous adsorption and the degree of spontaneity of the reaction increased with increasing temperature. Positive values of H degrees showed that the adsorption process was endothermic in the experimental temperature range. The results indicated that Pb(II)-imprinted PEI-functionalized silica sorbents could be employed as an effective material for the selective adsorption of Pb(II) ions from aqueous solutions.