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

Abstract

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.