"REMOVAL AND RECOVERY OF PHOSPHATE FROM CONTAMINATED WATER"

Abstract

Phosphate, being a harmful chemical for aquatic life results in the reduction of biodiversity due to the process of eutrophication and therefore, it becomes essential to remove phosphate from water. On the other hand, recovering phosphate from phosphate-containing wastewater becomes an alternative source of phosphorous which ultimately helps in overcoming the global challenge of phosphorus scarcity. Many studies deal with the biological and physico-chemical treatment processes of removing phosphate from contaminated water/wastewater. Present study deals with a viable fixed-bed process which can essentially eliminate phosphate from contaminated water/wastewater. A phosphate selective adsorbent (HFO-lRA67) has been prepared by using a weakly basic anion exchanger 1RA67 as the host material in which 1-IFO nanoparticles have been dispersed. The resulting hybrid sorhent combines durability, chemical stability and mechanical strength of polymeric weak base anion exchange resins with high sorption affinity of dispersed nanoparticles of Ferric hydroxide. It is also amenable to efficient regeneration. Phosphate adsorption in batch study satisfactorily fitted to the Freundlich isotherm, whereas the adsorption kinetics can he best described by inter-particle diffusion process. Phosphate adsorption is optimal at around p1-I 7.0 i.e. typical secondary wastewater p1-I conditions. Phosphate adsorption, which is driven by the fbrmation of Inner-sphere complexes. is observed to he not much affected by the presence of other competing anions....lie tests on Column which use synthetic phosphate solution confirmed the phosphate removal ability of hybrid adsorbent in the presence of other competing anions, for more than 3000 bed volumes. The exhausted bed is observed to be amenable to efficient regeneration with a NaOH-NaCI solution l'or repeated use without any significant loss of capacity. Similar results were obtained when the tests were carried out for secondary effluents of different wastewater treatment plants.