Removal of Pb(II) ions from aqueous solutions using functionalized cryogels

In this study, a poly(allylamine-co-methacrylamide-co-acrylic acid) (p(AA-co-MA-co-AAc)) cryogel containing amine and carboxyl groups was prepared and subsequently functionalized with thiourea using methyl isothiocyanate. The functionalized p(AA-co-MA-co-AAc) cryogel was then applied to the adsorption of lead (Pb) ions from aqueous solution, and the amount of Pb adsorption was measured. The functionalized p(AA-co-MA-co-AAc) cryogel was analyzed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), and its chemical structure, pore shape, pore distribution and specific surface area were confirmed. To determine the effect of the solution pH and initial concentration on Pb adsorption by the functionalized p(AA-co-MA-co-AAc) cryogel, Pb adsorption tests were performed. The functionalized p(AA-co-MA-co-AAc) cryogel exhibited the highest adsorption amount at pH 7 and 400 mg L^-1. The Pb adsorption process was determined to occur through chemical adsorption because the experimental data were fit well by a pseudo-second-order model. In addition, the equilibrium isotherm data fit the Langmuir isotherm better than the Freundlich model, indicating that the functionalized p(AA-co-MA-co-AAc) cryogel surfaces were uniform and that a lead adsorbate monolayer formed at equilibrium.