Removal of nitrate and Cr(VI) from drinking water by a macroporous anion exchange resin

Nitrate and hexavalent chromium (Cr(VI)) are potentially hazardous to human health and ecosystems. In this study, an anion exchange resin (PBO-8) was synthesized for the removal of nitrate and Cr(VI) from aqueous solution. The PBO-8 resin was characterized with Fourier transform infrared spectroscopy, scanning electron microscopy and BET surface area analyses. The results of batch adsorption experiments indicated that the maximum equilibrium uptake of nitrate and Cr(VI) in single solute solutions were 21.13 and 45.02 mg/g, respectively. The maximum quantity of PBO-8 resin for the adsorption of nitrate and Cr(VI) were, respectively, decreased to 14.17 and 27.03 mg/g in a nitrate and Cr(VI) binary solution. The increase in temperature and decrease of pH enhanced the capacity of the PBO-8 resin for Cr(VI) adsorption, but such effects were less significant for nitrate. The Gibbs free energy change, enthalpy change, and entropy change illustrated that the adsorption of aqueous nitrate and Cr(VI) were feasible, endothermic, and spontaneous. Furthermore, the behaviors of the nitrate and Cr(VI) adsorption onto the PBO-8 resin showed a better fit to the Langmuir isotherm and pseudo-second-order kinetic models. Intraparticle diffusion was the rate-limiting step.