Multi-win situation of wastewater purification, carbon emission reduction and resource utilization: Conversion of refractory organics and nitrate to urea and ammonia in a flow-through electrochemical integrated system.

The advanced oxidation process is an efficient technology for the degradation and detoxification of refractory organics to ensure water safety. However, most researches focus on improving pollutant degradation but overlook carbon emission and resource utilization. In this study, a flow-through electrochemical integrated system was constructed to simultaneously realize bisphenol A (BPA) oxidation into small non-toxic organics and CO, and generated CO coupled with nitrate-containing wastewater conversion to urea and ammonia on a porous cathode (Zr-Fe/CN). The synergistic effect between anodic BPA oxidation with cathodic CO and NOreduction improves the electron utilization efficiency and thus increasing the BPA degradation, urea yield rate (UYR) and NH yield rate (NYR) by 13.4 % 18.4 % and 8.3 %, respectively. Furthermore, the flow-through operation mode significantly increased the mass transfer efficiency and quickly carried generated CO from the anode into the cathode to improve CO utilization efficiency. Compared to the parallel plate electrode reactor, the BPA degradation efficiency, UYR and NYR in the flow-through reactor increased from 59.46 % to 84.49 % (the initial concentration of BPA was 40 mg/L), 9.94 mmol hg to 19.55 mmol hg, and 80.31 mmol hg to 106.06 mmol hg within 60 min, respectively. Moreover, the total carbon conversion efficiency (from BPA to urea) increased from 20.2 % to 42.4 % and the total Faraday efficiency (FE) increased from 78.6 % to 96.3 %. This work provides a multi-win strategy of harmless, resource-based and carbon emission reduction for wastewater treatment.