Kinetics, equilibrium and thermodynamic study of Cr(VI) sorption into toluidine blue o-impregnated XAD-7 resin beads and its application for the treatment of wastewaters containing Cr(VI)

The paper presents a novel support for Cr(VI) sorption and its removal from wastewaters. The support is a new extratant-impregnated resin, EIR. Toluidine blue o as an extractant was impregnated onto/into Amberlite XAD-7 beads, and kinetics, equilibrium and thermodynamic aspects of Cr(VI) sorption were investigated. An eluent solution having concentration of 0.1 M respect to NH3 and NaCl was used for regenerating new EIR and the concentration of Cr(VI) was measured spectrophotometrically. The maximum adsorption of Cr(VI) on/in TBO-impregnated XAD-7 occurs at pH range of 3.0–4.0. The results obtained from equilibrium adsorption studies were fitted in Langmuir model of adsorption. The thermodynamic parameters of Cr(VI) adsorption onto/into EIR beads were estimated. The kinetic studies were showed that t1/2 was less than 5 min and equilibrium could be obtained in 50 min. The pseudo-second-order kinetics model fitted with kinetic data. It also was observed that after rapid saturation of surface and big pores, the intra-particle diffusion is the only mechanism of Cr(VI) sorption into new EIR. The performance of new EIR under flow conditions was also studied and the results indicate that columns packed with TBO-impregnated XAD-7 beads can be effectively used for treating wastewaters containing Cr(VI).