Electrochemical oxidation of tannic acid contaminated wastewater by RuO2/IrO2/TaO2-coated titanium and graphite anodes

Abstract

The electrochemical oxidation of tannic acid contaminated wastewater by RuO2/IrO2/TaO2-coated titanium and graphite anodes has been investigated. The effect of the process variables, such as initial pH, current density, processing time, concentration of the electrolyte and anode materials, on the degradation of tannic acid was studied. During the various stages of electrolysis, parameters such as COD, chloride ion concentration and UV-Vis spectra were examined and discussed. The maximum chemical oxygen demand (COD) removal efficiency of 94% was achieved at pH 5, operated at the current density of 8.10 mA/cm2, electrolyte (NaCl) concentration of 0.1 M and at 60 min of electrolysis using graphite anodes. The experimental results showed that the electrochemical oxidation process could effectively reduce the COD from the tannic acid contaminated wastewater. An acidic pH showed the maximum reduction of COD compared with neutral and alkaline pH. Increase in current density, process time and electrolyte (NaCl) concentration with the increase in COD removal. Graphite anodes showed maximum removal of COD and better tannic acid degradation when compared with RuO2/IrO2/TaO2-coated titanium anodes.