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A novel poly(methacrylic acid)-grafted-cellulose/bentonite (Cellu-g-PMAAc/Bent) superabsorbent composite was prepared through graft copolymerization reaction among cellulose, methacrylic acid, and bentonite in the presence of N,N 0 -methylenebisacrylamide as a crosslinker and potassium peroxydisulphate as an initiator. The structural and morphological characteristics of the graft copolymer were determined using Fourier transform infrared spectra, scanning electron microscopeenergy dispersion analysis, and X-ray diffraction. The effectiveness of the Cellu-g-PMAAc/Bent, as adsorbent for the removal and recovery of uranium(VI) from aqueous media, was studied. The effects of pH, contact time, and initial sorbate concentration were studied to optimize the conditions for maximum adsorption. The adsorption process, which was pH dependent, shows maximum removal (>99.0% ) at pH 6.0. Kinetic study showed that 180 min of contact at 100 mg/L could adsorb about 99.2% of U(VI) onto Cellu-g-PMAAc/Bent. A pseudosecond-order kinetic model successfully described the kinetics of sorption of U(VI). Adsorption equilibrium data were correlated with the Langmuir, Freundlich, and Redlich-Peterson isotherm models. The best fit was obtained with Freundlich model. Desorption of U(UI) was studied by using 0.1M HCl. Adsorption/ desorption for more than six cycles showed the possibility of repeated use of this graft copolymer for the recovery of U(VI) from aqueous solutions.

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This study concerns with the development of a new adsorbent, iron(III) complex of an amino-functionalized polyacrylamide-grafted coconut coir pith (CP), a lignocellulosic residue, for Cr(VI) in water and industry effluents. The adsorbent (AM-Fe-PGCP) was characterized by FTIR, EDS, Mö ssbauer, surface area analyzer, TG/DTG, and potentiometric titration. The effects of contact time, initial sorbate concentration, pH, dose of adsorbent, and temperature on Cr(VI) adsorption were studied to optimize the conditions for maximum adsorption. The kinetics of sorption was investigated using pseudo-first-order and pseudo-second-order rate equations with the later giving a better fit to the experimental data. The mechanism of sorption was found to be film diffusion controlled. The Langmuir isotherm model yields a much better fit than the Freundlich and Dubinin-Radushkevich models with maximum adsorption capacity of 142.76 mg/g at 30 C. Simulated industry wastewater sample was treated with AMFe-PGCP to demonstrate its efficiency in removing Cr(VI) from wastewater. The alkali treatment (0.1M NaOH) and re-introduction of Fe 3þ lead to a reactivation of the spent adsorbent and can be reused through many cycles of water treatment and regeneration without any loss in the adsorption capacity.