Formic acid recovery from EDTA wastewater using coupled ozonation and flow-electrode capacitive deionization (Ozo/FCDI): Performance assessment at high cell voltage

Carbon resource recovery from toxic organic wastewater to reduce unnecessary energy loss and greenhouse gas emissions is rarely pursued. In the present study, a promising approach for formic acid (FA) recovery from EDTA wastewater was proposed by coupling ozonation and flow-electrode capacitive deionization (Ozo/FCDI). In the ozonation process, a FA productivity of 25% was obtained with the complete degradation of EDTA. The FA recovery from wastewater was compared under electrodialysis (i.e., without the use of flowable carbon electrodes, 0 wt%) and FCDI (i.e. using 5 wt% flowable carbon electrodes) processes and the results demonstrated the superiority of the FCDI process. After 390 min of operation, the accumulated FA concentration in the anode chamber of the FCDI system had increased to 633.6 mg/L with a low energy consumption of 8.0 kWh/kg FA, which was 1.8 times of the FA concentration in the electrodialysis (ED) process and nearly 6.4 times in the feed stream. These findings suggest the effective acquisition of high value-added FA in the Ozo/FCDI system; may provide new opportunities and challenges for the recovery of organic compounds.