Effects of storage conditions, pH and Mg:P ratio on the precipitation process for phosphate recovery

Abstract

Phosphorus (P) is an essential yet non-renewable nutrient, so recovering it from urine is getting more attention since it has a high concentration of nutrients. This study aimed to investigate the impacts of temperature, storage condition on urine's characteristics, and the effects of pH, Mg:P ratio, and calcium (Ca) ion on yielded magnesium phosphate hydrate (Mg3(PO4)2•xH2O) crystallization from fresh urine. The results indicated that the urine stored at 4 °C in a sealed environment created less spontaneous precipitation. The findings showed that the favorable condition for Mg3(PO4)2•xH2O recovery was at pH 10.5 and Mg:P of 1.3. The XRD analysis confirmed that P was crystallized as Mg3(PO4)2•xH2O phase with an average particle size of 0.5 mm. Furthermore, SEM-EDS images suggested the Ca and K might co-precipitate with Mg3(PO4)2•xH2O. These findings indicate that the potential of P recovery from nutrient-rich wastewater can both reduce environmental pollution and profit from phosphate fertilizers.

Keywords

• Urine
• Phosphate recovery
• Crystallization
• Wastewater treatment
• Magnesium phosphate hydrate