(2ij) Enhanced Electrochemical Struvite Precipitation from Phosphate-Rich Wastewater Using Pulsating Voltage

Fatigue failure of thin film under fluctuating electrical stress has been reported to occur at relatively lower electric field strength than in constant field experiments. An analogy may be extended to an electrochemical system where pulsating (dynamic) potential may be hypothesized to aggravate rupture of passive magnesium hydroxide film on pure magnesium anode. Enhanced rupture of the passivating film on applying a dynamic versus constant voltage may be expected to increase magnesium dissolution and subsequently, phosphate recovery as struvite (MgNH₄PO₄.6H₂O) precipitates during electrolysis of phosphate rich wastewater with a chloride background. Present investigation was attempted in an electrochemical cell consisting of pure magnesium anode using both simulated and real wastewater feedstock. The mean potential was tentatively chosen at a voltage just above the pitting potential. Frequency of the voltage waveform (1-100 Hz) was varied to maximize phosphate recovery per unit magnesium dissolution and energy consumption. Overall, a 40% increase in precipitate yield was obtained in the pulsating voltage. Outcomes of this study may be anticipated to demonstrate the advantage of dynamic anode potential in combatting electrode fouling and enhancing struvite precipitation.