Electrochemical destruction of RB5 on Ti/PtOx-RuO2-SnO2-Sb2O5 electrodes: a comparison of two methods for electrode preparation

The studies were performed with 100 mg/L of Reactive Black 5 dye (RB5) in batch reactors on Ti/PtOx-RuO2-SnO2-Sb2O5 electrodes prepared indigenously. The electrodes were fabricated using titanium substrate (plate) and coated with mixed metals of a fixed composition by standard thermal decomposition (STD) and polymeric precursor thermal decomposition (PPTD) methods. The electrolysis up to 1 h was accomplished at a constant current density of 50 mA/cm(2). For the process, an initial pH of 2 was maintained with the dosage of 4 g/L NaCl as supporting electrolyte. The effects of electrodes on colour, chemical oxygen demand, and total organic carbon removal were investigated for destruction of RB5. In this comparative study, while complete decolourizations of water containing RB5 were achieved on the electrodes prepared by STD and PPTD methods, but COD and TOC removal was found to be different for different electrodes at operating conditions. The 87% COD and 83% TOC removals were achieved on Ti/PtOx-RuO2-SnO2-Sb2O5 electrode prepared by PPTD method, in comparison to 83% COD and 80% TOC removals on the electrode prepared by STD method. The two types of electrodes were compared based on removal rate constant, mass transfer coefficient, instantaneous current efficiency, energy consumption, and accelerated life test. The energy demand for RB5 removal in this study was less than 250 kWh/kg COD, which is much lower than the reported values in similar studies. Further, the performance of electrodes was compared employing scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction analysis for coating deposited on Ti substrate, and also by cyclic voltammetry.