Solar photoelectrocatalytic degradation of Acid Orange 7 with ZnO/TiO2 nanocomposite coated on stainless steel electrode

Dyes, especially azo dyes, are among the most applicable compounds in textile and dyeing industries. Using the photoelectrocatalytic method for degrading wastewaters has recently attracted researchers' attention. By using the potential difference between anode and cathode in these systems, the lifetime of electron-hole pairs formed by photocatalysts increases, and the possibility of their recombination decreases to the least possible extent. In this investigation, the photoelectrocatalytic process was used for removing synthetic wastewater under solar irradiation with graphite cathode and stainless steel anode coated by ZnO/TiO2 nanocomposite. A LC-Mass test was performed on wastewater to investigate its products; the energy consumption was also calculated and optimized. The results showed that the process' optimum condition of the effective parameters included current density = 1 mA/cm2, pH 6.5, without aeration, dye concentration = 100 mg/L and electrode area = 30 cm2. Under these conditions, the dye removal efficiency after 180 min and COD removal after 270 min were 97% and 99%, respectively, and the energy consumption was 0.19 kWh/kg. Based on the results, the photoelectrocatalytic method is a powerful method for removing organic compounds especially in wastewater degradation containing the dye and persistent pollutants because it enhances hydroxyl radical production.