Energy-Efficient Electrocoagulation Under Pulsed Voltage: Toward Sustainable Phosphate Capture and Water Circularity

Electrocoagulation (EC) is an electrochemical wastewater treatment technique that removes contaminants via in situ generation of metal (oxy)hydroxide coagulants from anode dissolution. This work investigates the effects of electrode pairing, waveform, and pulse frequency, and their synergy on phosphate removal. An SS-304 anode was paired with an SS-304 or Al6061 cathode, and the hybrid SS(A)-Al(C) combination achieved accelerated removal (69.9%) in 20 min compared to the similar SS(A)-SS(C) (45.2%) configuration. Pulsed direct voltage (PDV) waveforms outperformed direct current (DC) and pulsed direct current (PDC) waveforms, and among 1, 5, and 10 Hz, 5 Hz PDV delivered the best balance between enhanced dissolution and capacitive losses. In PDV mode, phosphate removals of 80.0% ± 1.3% and 99.9% ± 0.1% were achieved within 20 and 120 min, respectively, with a removal efficiency of 186.5-208.7 g PO₄ ^3-/kWh at 20 min, approximately threefold that achieved by DC/PDC. Moreover, the PDV setup achieved a Faradaic efficiency exceeding 74.0%, substantially outperforming the PDC (5.6%) and DC (4.7%) modes, demonstrating that voltage pulsing mitigates anode passivation and improves energy efficiency. These findings reveal that combining a 5 Hz PDV waveform and dissimilar SS(A)-Al(C) electrode configuration offers an energy-efficient and scalable approach for rapid phosphate removal and water circularity.