Sustainable electrochemical process for recovery of metal ions in synthetic mining wastewater and their utilization in photocathodic CO2 reduction into formic acid

The recovery and utilization of metal ions from mining and industrial wastewater are highly desirable to turn waste into wealth. Herein, polyaniline decorated date seed-derived activated carbon (PANI-DSAC) has been successfully used as an electrode for the capacitive deionization of Fe2+ and Cu2+ ions in synthetic mining wastewater. Symmetrical assembly of the PANI-DSAC CDI electrodes recovered 99% of the Fe2+ and Cu2+ ions from synthetic mining wastewater via several redox reactions. The mechanism of redox reactions and electrosorption of multiple metal ions has been demonstrated. In addition, the recovered metal ions by PANI-DSAC were then successfully converted to CuFe2O4/CFs-DSAC via the thermochemical conversion process. Further, CuFe2O4/CFs-DSAC was successfully used as a photocathode to reduce CO2 into formic acid. The results demonstrate that recovered valuable metal ions from mining wastewater can be utilized to fabricate high-performing functional electrocatalytic materials for energy conversion and storage applications.