Through converting the surface complex on TiO₂ nanorods to generate superoxide and singlet oxygen to remove CN

Cyanide (CN^-) is extensively used in the process of plating devices and for surface treatment in the electroplating industry and is extremely hazardous to humans and the environment. Peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) hold considerable promise for CN^- removal. However, the activity of sulfate radical and hydroxyl radical generated in the PMS activation process is low in the base condition, leading to a drop in its efficiency in CN^- removal. Thus, a photo-electrocatalytic system (PEC), developed using a TiO₂ photoanode and a carbon aerogel cathode, was used to activate PMS for the removal of CN^- from wastewater through the generation of radicals and non-radicals. The PEC/PMS system could effectively remove CN^-, with the removal efficiency reaching 98.5% within 2 min, when PMS concentration was at the 0.25 mmol/L level, and the applied bias voltage was -0.5 V. The main active species in the PEC/PMS system were superoxide radicals and singlet oxygen, which was proved through electron paramagnetic resonance detection and quenching experiments. Results obtained through in-situ Raman measurements, photocurrent tests, and electrochemical impedance spectroscopy measurements indicated that the TiO₂ could activate PMS to generate active species. Following many cycles of experimentation, it was discovered that the system displayed high catalytic performance and possessed satisfactory stability to remove CN^- economically and efficiently.