Effect of pH on the Ammonia-nitrogen Removal Rate by Chemical Precipitation

摘要

The effect of pH on ammonia nitrogen removal rate was studied theoretically and experimentally by chemical precipitation with MgCl<,2>·6H<,2>O and Na<,2>HPO <,4>·12H<,2>O as precipitator and with simulative wastewater and coking wastewater after ammonia still. The theoretical calculation shows that the optimal pH is 8.89 by chemical precipitation, which has nothing to do with initial concentration of ammonia nitrogen. The results show that, for the simulative wastewater, when pH=9.0 and the mol ratio of PO<'3-><,4>/NH<,4 +>/Mg<'2>+ is 1.3/1/1.2, the removal rate of ammonia nitrogen is maximal (97.3%), the ammonia nitrogen concentration decreases from 592.8 mg/L to 15.8 mg/L. For the coking wastewater after distillation with ammonia nitrogen concentration of 851.6mg/L, at condition of pH=9.0 and the mol ratio of PO<'3-> <,4>/NH<,4+>/Mg<'2+>/is 1.4/1/1.4, the maximal removal rate of ammonia nitrogen is 86.7%.