Simultaneous removal of ammonia and phosphate by electro-oxidation and electrocoagulation using RuO-IrO/Ti and microscale zero-valent iron composite electrode.

Electro-oxidation using RuO-IrO/Ti plate anode and electrocoagulation using iron plate anode were widely applied to remove ammonia and phosphate in an aquatic environment, respectively. In this work, we designed magnetically bound ZVI microparticles on RuO-IrO/Ti plate as a composite electrode for the simultaneous removal of ammonia and phosphate from aqueous solution via combined EO and EC (EO/EC) processes. We present a series of experiments to study such simultaneous removal under an electric field via the EO/EC process. In the electrochemical unit, mZVI-RuO-IrO/Ti, mZVI-graphite, and RuO-IrO/Ti electrodes were used as anodes. The influence of applied voltage, initial pH, zero-valent iron dosage, reaction temperature, and organic compounds on the EO/EC process was also examined. Ammonia and phosphate could be completely removed at an applied voltage of 10 V, pH of 7, zero-valent iron dosage of 0.1 g, and reaction temperature of 35 °C using mZVI-RuO-IrO/Ti anode when influent ammonia and phosphate concentrations is 200 and 100 mg L. Ammonia degradation was consistent with pseudo-zero-order kinetic model. The characterization was analyzed by scanning electron microscope-energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Hence, the mZVI-RuO-IrO/Ti electrode can be used for efficient simultaneous removal of ammonia and phosphate.