Development of an effective operation system in a magnesium-air desalination cell for electricity production with nitrogen and phosphorus removal

Abstract

A magnesium-air desalination cell system is developed for electricity production alongside concurrent desalination and wastewater treatment. Synthetic wastewater at three concentrations is used as an anolyte and catholyte with and without a recirculation system to investigate effective operation methods. The operation time was 20 h, and the anolyte was changed every 3 h. The maximum conductivity reduction efficiency (desalination efficiency) at a high concentration of synthetic wastewater was 77.4 % and 51.6 % in operation systems with and without recirculation, respectively. Measured concurrently, the maximum electric energy production (EEP) was 23.8 Wh m−3 in the system with recirculation and 15.6 Wh m−3 in the system without recirculation. The increase of voltage drop in operation without recirculation was due to the high internal resistance of the membrane induced to lower EEP in contrast to the membrane in operation with recirculation. During operation, struvite was produced at high initial concentration of synthetic wastewater in bulk solution and confirmed through Fourier transform-infrared spectroscopy and X-ray diffraction. Ammonia and phosphorous removal was high at high initial concentration of synthetic wastewater. The results indicate that the magnesium-air desalination cell holds great potential for electricity production, salt reduction, and wastewater treatment.