Amberlite IRA-900 Ion Exchange Resin for the Sorption of Selenate and Sulfate: Equilibrium, Kinetic, and Regeneration Studies

The synthetic strong base anion-exchange resin Amberlite IRA-900 was investigated for its adsorption capacity to simultaneously remove selenate (${\mathrm{SeO}}_4^{2-}$) and sulfate (${\mathrm{SO}}_4^{2-}$) from single and binary anion solutions at pH 7.5 and 20°C. At an initial ${\mathrm{SeO}}_4^{2-}$ and ${\mathrm{SO}}_4^{2-}$ concentration of 428.9 and $\mathrm{1,441.1}\mathrm{mg}/\mathrm{L}$, respectively, IRA-900 adsorbed 85 ($\pm 1$)% ${\mathrm{SeO}}_4^{2-}$ and 75 ($\pm 5$)% ${\mathrm{SO}}_4^{2-}$ from single anion solutions at 2% ($w/v$) resin dosage. In binary anion solutions, a 20% decrease for both the ${\mathrm{SeO}}_4^{2-}$ and ${\mathrm{SO}}_4^{2-}$ adsorption efficiency was observed. Batch kinetic experimental data indicated that the adsorption rate of IRA-900 for both ${\mathrm{SeO}}_4^{2-}$ and ${\mathrm{SO}}_4^{2-}$ in the single and binary anion solutions fitted well to the pseudo-second-order kinetic model ($R^2=0.99$). The modified Langmuir isotherm complete competition model best fitted the experimental data for binary anion solutions, showing 24% and 10% average relative error from theoretical calculations for ${\mathrm{SeO}}_4^{2-}$ and ${\mathrm{SO}}_4^{2-}$, respectively. Exhausted resin was regenerated for the next cycle of adsorption using either 0.25 or 0.5 M HCl for 20 min and was tested for 30 adsorption-desorption cycles. Results showed that the resin was suitable for reuse at an optimal adsorption-desorption of 6 cycles without compromising the removal efficiencies. Efficient and fast adsorption of both ${\mathrm{SeO}}_4^{2-}$ and ${\mathrm{SO}}_4^{2-}$ is promising for developing an IRA-900 based ion-exchange process for the remediation of Se-contaminated (waste)waters.