NITRATE AND PHOSPHATE RECOVERY FROM ANION-EXCHANGE RESINS

The recovery of nitrate and phosphate from two anion exchange resins was determined. A general purpose and nitrate-selective resin were extracted with potassium chloride (KCl), acidified ammonium chloride (NH4Cl), and sodium sulfate (Na2SO4). The recovery of both nitrate and phosphate were significantly affected by the choice of resin and extractant. The combination of Na2SO4 extractant and nitrate-selective resin resulted in less than half as much nitrate recovery as any other combination of resin and extractant. Consequently, if it is important to recover nitrate from the resins, Na2SO4 should not be used. Greater quantities of phosphate were recovered from the nitrate selective resin with all extractants. However, phosphate recovery was not significantly affected by choice of extractant. More rigorous extraction was required for the nitrate-selective resin to achieve a level of nitrate recovery comparable to the general purpose resin. The nitrate selectivity also resulted in less phosphate being adsorbed from solutions high in nitrate. Finally, new batches of resin should be tested because differences between them can be significant.