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Bentonite has been studied extensively because of its strong sorption and complexation ability. In this work, the sorption of Se(IV) on purified GMZ bentonite was investigated under ambient temperature as functions of contact time, pH, Se(IV) concentration and co-existing ion Eu(III) using batch techniques. Sorption kinetics of Se(IV) was successfully described by the pseudo-second-order rate equation. The sorption amount of Se(IV) was strongly dependent on the solution pH, and a positive effect was observed on Se(IV) and Eu(III) co-sorption when these two elements existed in the same system under high surface coverage of sorbent. Double layer model was set up and used to quantitatively interpret the sorption experimental data collected in binary and ternary sorption systems. From the experimental results, one can conclude that GMZ bentonite may have good potentialities for immobilizing selenium in nuclear wastes. [ABSTRACT FROM AUTHOR]

Abstract: Novel magnetic organo-bentonite-Fe3O4 poly(sodium acrylate) (OB-Fe3O4 PSA) superabsorbent nanocomposites were synthesized in aqueous solution through the copolymerization of partially neutralized acrylic acid (SA) on OB-Fe3O4 nanoparticle by using N,N′-methylenebisacrylamide as crosslinker and ammonium persulfate as initiator. This new superabsorbent was characterized by FTIR, TGA, FE-SEM and XRD. Its iron content and magnetic properties were studied by using inductively coupled plasma (ICP) and a vibrating sample magnetometer (VSM), respectively. The water retention test of OB-Fe3O4 PSA was also performed. The introduced OB-Fe3O4 could form a loose and coarse surface and improve the water absorbency of OB-Fe3O4 PSA superabsorbent. The effects of pH, ionic strength, and humic substances (HS) on the adsorption of Th(IV) were investigated in detail through batch experiments. The maximum adsorption capacity (Qmax ) of Th(IV) on OB-Fe3O4 PSA 3.6 superabsorbent at pH 3.0±0.05 and T=298K was about 6.55mmol/g, higher than any value previously reported. The thermodynamic parameters calculated from temperature-dependent adsorption isotherms suggested that Th(IV) adsorption on OB-Fe3O4 PSA superabsorbent was an endothermic and spontaneous process. Furthermore, OB-Fe3O4 PSA superabsorbent could be regenerated through the desorption of Th(IV) using 0.1mol/L HCl solution and the adsorption capacity was still higher than 3.6mmol/g after five consecutive adsorption–desorption processes. [Copyright &y& Elsevier]