Alleviating Na effect on phosphate and potassium recovery from synthetic urine by K-struvite crystallization using different magnesium sources.

Author(s) Huang, H.; Zhang, D.; Wang, W.; Li, B.; Zhao, N.; Li, J.; Dai, J.
Journal Sci Total Environ
Date Published 2019 Mar 10

Human urine is characterized by high concentrations of nitrogen (N), phosphorus (P) and potassium (K), of which the P and K can be recovered as K-struvite crystals. This study first investigated the formation of Na-struvite because of the high Na present in the urine. From the results, the optimal pH for the Na-struvite crystallization was observed to be 12, and the rise in the Na concentration distinctly favored the Na-struvite formation. As magnesium needed to be added to induce the K-struvite crystallization, several magnesium sources including MgCl, Mg sacrificial electrode and Mg(OH) were applied to recover P and K from synthetic urine. The findings indicated that when MgCl was used as the magnesium source, the K removal could be slightly enhanced by prolonging the reaction time, which would correspondingly decrease the Na concentration in the precipitates; besides, the intermittent addition of MgCl could noticeably improve the removal efficiency of K by 6%, but simultaneously raise the Na content in the precipitates recovered. With respect to the use of the Mg sacrificial electrode, the recovery efficiencies of the P and K from synthetic urine were close to those with the use of MgCl. However, when Mg(OH) was used as the magnesium source, the recovery efficiencies of P and K achieved only roughly 50%, which was much lower than those noted when MgCl and the Mg sacrificial electrode were employed. A comprehensive analysis revealed that the MgCl was the best magnesium source for the K-struvite crystallization, followed by the Mg sacrificial electrode and Mg(OH).

DOI 10.1016/j.scitotenv.2018.11.259
ISSN 1879-1026
Citation Sci Total Environ. 2019;655:211219.

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