Graft Copolymerization of Crosslinked Polyvinyl Alcohol with Acrylonitrile and Its Amidoxime Modification as a Heavy Metal Ion Adsorbent

Polyvinyl alcohol (PVA) hydrogel was crosslinked with glutaraldehyde. The crosslinked polyvinyl alcohol (CPVA) was grafted with acrylonitrile using cericammonium nitrate as an initiator (CPVA-PAN), and then modified by hydroxylamine hydrochloride (CPVA-AO-PAN). CPVA, CPVA-PAN, and CPVA-AO-PAN were characterized by Fourier Transform Infrared spectroscopy. Cu2+ adsorption by CPVA-AO-PAN reached the equilibrium at contact time of 40 h with a adsorption capacity of 40.7 mg g(-1). The effects of initial metal concentration, adsorption time, and pH on adsorption capacity were investigated, respectively. Pseudo-first-order and pseudo-second-order models were employed to evaluate the adsorption kinetics, with the R-2 values of 0.9524 and 0.9972, respectively. Langmuir and Freundlich isotherm models were compared, and the Langmuir model shows high goodness-of-fit. The adsorption process was endothermic and spontaneous, as evidenced by the positive increment H and the negative increment G.