Effect of ammonium/phosphate molar ratio on struvite production via electrolysis using a sacrificial magnesium anode
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Abstract
Excessive ammonium and phosphate levels in aquatic environments potentially cause eutrophication, leading to water quality imbalance, algal blooming, and disturbance of biodiversity status. Electrolysis using a sacrificial magnesium anode effectively removes and recovers ammonium and phosphate, producing struvite (MgNH4PO4.6H2O). The present study investigated the optimum current density and the effect of the ammonium/phosphate molar ratio on struvite production. The current density was controlled at 10, 50, and 100 mA/cm2. An artificial wastewater containing [NH4+]:[PO43-] in a molar ratio of 1:10, 1:1, and 10:1 was used as the test solution. The optimum current density was determined as 50 mA/cm2. The ammonium and phosphate reduction ratios at a 1:1 molar ratio was approximately 46.91% and 74.26%, respectively. Increasing the ammonium molarity in the test solution to 10:1 increased the phosphate reduction ratio to 96.38% while decreasing the ammonium reduction ratio to 26.28%. The maximum precipitation of 4.1914 g was generated at a molar ratio of 10:1 with a specific energy consumption of 0.011 Wh/mg-P, out of the three ammonium/phosphate molar ratio variations. Microscopes and SEM-EDS were used to characterize the precipitates produced, and Visual MINTEQ 3.1 was then used for modeling.
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