Isotherm adsorption studies of Ni(II) ion removal from aqueous solutions by modified carboxymethyl cellulose hydrogel

This paper reports the removal of nickel ions from aqueous solutions using carboxymethyl cellulose-graft-poly(acrylic acid) CMC-g-PAA hydrogel as an adsorbent. The hydrogel was prepared through graft copolymerization of acrylic acid monomer onto a carboxymethyl cellulose backbone in the presence of N,N'-methylenebisacrylamide as a crosslinking-agent using benzoyl peroxide initiator system. Isotherm for the adsorption of nickel on CMC-g-PAA hydrogel was developed and the equilibrium data fitted to the Langmuir and Freundlich isotherm models. The result showed that at pH of 5 and shaker speed of 100 rpm, Freundlich model was better fitted than Langmuir model, of which R-2 = 0.999 and R-2 = 0.935, respectively. The constant of Langmuir model was K-L value = 0.003 and q(max)= 1000 mg/g, whereas the constant of Freundlich model n = 1.2 and K-F = 4.614. The CMC-g-PAA hydrogel before and after Ni(II) adsorption were characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR).