Removal of nitrate and phosphate anions from aqueous solutions using strong base anion exchange resin

The present study investigates the potential of a commercially available anion exchange resin namely Duolite A 171 (DA 171) as an adsorbent for the removal of nitrate and phosphate from the anionic aqueous solutions in batch mode. Effects of various parameters such as contact time, dosage of adsorbent, pH of the aqueous solutions, competitive co-anions, and temperature on the sorption capacity of the sorbent were studied. Adsorption from the nitrate/phosphate binary coexisting system was also done. Regeneration of the sorbent was carried out using 0.025M NaCl solution. The desorption study showed that even after fifth regeneration cycle, the adsorption efficiency of DA 171 resin for nitrate and phosphate remained as 99.8 and 99.5%, respectively. The negative H degrees values revealed that the adsorption of nitrate and phosphate is exothermic processes. Fitting of Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) adsorption models to the equilibrium data were investigated. The adsorption capacity of nitrate (Q degrees) derived from Langmuir isotherm was 123.63mg/g and of phosphate derived from D-R isotherm was 43.95mg/g. The pseudo-second-order and particle diffusion kinetic models were the applicable kinetic models in both the cases. The adsorbent was characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy.