Characterization and evaluation of a macroporous anion exchange resin for nitrate removal from drinking water

The traditional drinking water purification process is inefficient in removing nitrate significantly. Ion exchange may be the most practical method for the removal of nitrate from drinking water. In this study, an anion exchange resin (PBE-8) was synthesized for selective nitrate removal. The PBE-8 resin was characterized by Fourier transform infrared spectrometry, scanning electron microscopy, and BET surface area analyses. Batch adsorption experiments were carried out to evaluate the thermodynamic and kinetic behaviors of the PBE-8 resin for the adsorption of nitrate. The results indicated that the maximum equilibrium nitrate uptake of PBE-8 was 26.19 mg N/g, which was higher than that of Purolite A 520E (23.07 mg N/g), but lower than that of HZ-222 (33.57 mg N/g). PBE-8 and Purolite A 520E demonstrated better adsorption of nitrate than HZ-222 in the presence of competing anions, such as sulfate, chloride, and bicarbonate in aqueous solution. The Gibbs free energy change (-12.15 to -1.15 kJ/mol), enthalpy change (0.35-7.73 kJ/mol), and entropy change (0.005-0.066 kJ/mol K) indicated that the adsorption of aqueous nitrate by PBE-8 was feasible, endothermic, and spontaneous. Furthermore, the nitrate adsorption by the PBE-8 resin showed a better fit to the Langmuir isotherm and pseudo-second-order kinetic models. Intraparticle diffusion was the main rate-limiting step.