Electrocatalytic Upcycling of Nitrate Wastewater into an Ammonia Fertilizer via an Electrified Membrane

摘要

Electrochemically upcycling wastewater nitrogen such as nitrate(NO_3~-)and nitrite(NO_2~-)into an ammonia fertilizer is a promising yet challenging research topic in resource j recovery and wastewater treatment.This study presents an electrified membrane made of a CuO@Cu foam and a polytetrafluoroethylene(PTFE)membrane for reducing NO3~ to ammonia(NH3)and upcycling NH3 into(NH4)2SO4,a liquid fertilizer for ready-use.A paired electrolysis process without external acid/base consumption was achieved under a partial current density of 63.8 ± 4.4 mA·cm~(-2)on the cathodic membrane,which removed 99.9% NO_3~-in the feed(150 mM NO_3~-)after a 5 h operation with an NH3 recovery rate of 99.5%.A recovery rate and energy consumption of 3100 ± 91 g·(NH4)2SO4·m~(-2)·d~(-1)and 21.8 ± 3.8 kWh·kg~(-1)·(NH4)2SO4,respectively,almost outcompete the industrial ammonia production cost in the Haber-Bosch process.Density functional theory(DFT)calculations unraveled that the in situ electrochemical conversion of Cu~(2+)into Cu~(1+)provides highly dynamic active species for NO_3~-reduction to NH3.This electrified membrane process was demonstrated to achieve synergistic nitrate decontamination and nutrient recovery with durable catalytic activity and stability.