Simultaneously converting synthetic fresh urine into high-quality artificial phosphate ores and urea solution: A novel coupled system of electrochemical selective separation plus induced precipitation

Both the sustainable development and environmental protection urge a demand of new paradigm to recover high-quality nutrients from source-separated urine, but the simultaneous recovery of phosphorus and nitrogen is difficult due to the complex composition. Herein, a coupled system consisting of a flow-electrode capacitive desalination and magnesium-air fuel cell (FCDI-MAFC) was proposed to accomplish electrochemical selective separation plus induced precipitation. The results showed that ionic species in urine were effectively separated from the non-ionic components to generate a urea solution with purity up to 99.7%. Ionic species were converted into artificial phosphate ores (APOs) with a phosphate content of 98.2%. The mass proportion of struvite in the APOs exceeded 90%. The energy consumption also decreased by 13% over five batches of operation. The overall results provide a novel method for the electrochemical selective separation and recovery of high-quality nutrients from complex wastewater.