Influence of Phosphate Concentration and PH Crystallization of Magnesium Ammonium Phosphate (MAP)

The influence of initial phosphate concentration and pH on reactants molar ratio in the process of magnesium ammonia phosphate (MAP) crystallization was investigated by using single factor analysis, and the crystal products with different reaction condition were also characterized through the XRD analysis to evaluate the MAP formation in the crystallization process. The experimental results showed that the optimum reactants molar ratio of n(NH4+):n(Mg2+):n(PO43-) were 90:25:1, 4:1.6:1 and 3:1.4:1 when pH value was 9.5 and initial phosphate concentrations were 8mg/L, 50mg/L and 100mg/L, respectively, resulted in the phosphate removal efficiencies were 95.5%, 97.6% and 99.0% correspondingly. It was observed that the phosphate removal increased with the improving of the initial phosphate concentration or pH value, even the reactants molar ratio of n (NH4+): n (PO43-) or n (Mg2+): n (PO43-) was lower than the optimum values. The XRD analysis revealed that the best MAP crystal could be produced with initial phosphate concentration 50mg/L and pH 9.0.