No abstract

Katira gum-graft-poly(N-vinyl imidazole) was synthesized in a water medium with potassium perdisulfate as the freeradical initiator at 70 6 1 8C. The graft copolymer was sulfated by chlorosulfonic acid in the presence of pyridine and formamide. Various characterization techniques, including Fourier transform infrared (FTIR) spectroscopy and field emission scanning electron microscopy, were used to characterize both the unsulfated and sulfated graft copolymers. The sulfated graft copolymer was used for the adsorption of Hg(II) ions from its aqueous solution. The operating variables affecting the Hg(II) adsorption, including the solution pH, amount of sulfated graft copolymer, contact time, and concentration of Hg(II), were investigated extensively. The sulfated graft copolymer was also used for competitive metal-ion removal with Pb(II), Cd(II), Cu(II), and Zn(II). Metal complexation was studied with FTIR spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, and cyclic voltammetry analysis. The Hg(II) adsorption data of the sulfated graft copolymer were described well by the pseudo-second-order rate equation. The Langmuir adsorption isotherm provided the best correlation for the adsorption data. Various thermodynamic parameters for the adsorption were calculated. FTIR and UV-vis spectroscopy and cyclic voltammetry analysis before and after the adsorption of Hg(II) on the sulfated graft copolymer showed that columbic attraction was mainly responsible for the binding of the Hg(II) ions with the ASO 2 3 groups present in the sulfated graft copolymer. The sulfated graft copolymer showed a better adsorption performance than the graft copolymer itself under optimized conditions.