Adsorption of perchlorate from aqueous solutions by anion exchange resins: Effects of resin properties and solution chemistry

In this study, the perchlorate sorption behaviors of three various representative anion resins were systematically investigated with respect to sorption kinetics, equilibrium capacity, perchlorate selectivity, thermodynamics and isotherms. Results showed that the equilibrium capacity of the three investigated resins followed the order of Purolite A530E≈magnetic ion exchange resin > Purolite A532E due to the effect of structure type, while magnetic ion exchange resin (MIEX) reached the equilibrium much faster than Purolite A530E and Purolite A532E, which can be attributed to its smaller particle size and larger surface area. Furthermore, the two Purolite resins showed superior perchlorate selectivity than MIEX resin because of matrix and functional groups. The adsorption kinetics for each of three selected resins fitted best with the pseudo-second-order model, indicating the adsorption process was controlled by chemical sorption. While the fitting of intra-particle model implied that intra-particle diffusion was not the only rate-limiting step of the whole process. The isotherm data can be best described by the Freundlich isotherm and the value of intensity of adsorption was larger than 1, suggesting the process was heterogenous and favorable adsorption. The negative ΔG° manifested that the adsorption of perchlorate by each of the three resins was a spontaneous process, and the positive indicated it was also an endothermic and entropy driven process. Besides, the effects of independent variables on the perchlorate sorption of the three resins were also evaluated completely. Results suggested that the removal of perchlorate increased with the increase of resin dosage and temperature for each of the three resins, and the sorption process was nearly independent of solution pH in a wide range of 4–10 for each of the resins.