Comparative study of the removal of direct red 23 by anodic oxidation, electro-Fenton, photo-anodic oxidation and photoelectro-Fenton in chloride and sulfate media.

This study aims to compare the efficiency of anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF), and their association with UV irradiation (photo anodic oxidation (PAO), and photo electro-Fenton (PEF) for the removal of Direct Red 23 from wastewater using a BDD/carbon felt cell in chloride and sulfate medium and in their combination. The effect of the supporting electrolyte was investigated in AO-H2O2 and EF processes. High discoloration efficiency was obtained in chloride media while a higher mineralization rate was achieved in sulfate media. The EF process reached higher total organic carbon (TOC) removal efficiency than AO-H2O2. 90% TOC removal rate was achieved by the EF against 82% by AO-H2O2 in sulfate media. The influence of using the mixt supporting electrolyte formed of 75% Na2SO4 + 25% NaCl was found to have beneficial effect on TOC removal, achieving 89% and 97% by AO-H2O2 and EF, respectively. High currents led to higher mineralization rates while low currents yielded to a higher mineralization current efficiency (MCE%) and lower energy consumption (EC). UV irradiation enhanced process efficiency. Mineralization efficiency followed the sequence: AO-H2O2 < PAO < EF < PEF. The PEF process was able to remove TOC completely at 5 mA cm-2 current density and 6 h of electrolysis with a MCE% value of 16.57% and EC value of 1.29 kWh g-1 TOC removed.

Nanostructured ZnO-TiO2 thin film oxide as anode material in electrooxidation of organic pollutants. Application to the removal of dye Amido black 10B from water.

Electrochemical oxidative degradation of diazo dye Amido black 10B (AB10B) as model pollutant in water has been studied using nanostructured ZnO-TiO2 thin films deposited on graphite felt (GrF) substrate as anode. The influence of various operating parameters, namely the current intensity, the nature and concentration of catalyst, the nature of electrode materials (anode/cathode), and the adsorption of dye and ambient light were investigated. It was found that the oxidative degradation of AB10B followed pseudo first-order kinetics. The optimal operating conditions for the degradation of 0.12 mM (74 mg L-1) dye concentration and mineralization of its aqueous solution were determined as GrF-ZnO-TiO2 thin film anode, 100 mA current intensity, and 0.1 mM Fe2+ (catalyst) concentration. Under these operating conditions, discoloration of AB10B solution was reached at 60 min while 6 h treatment needed for a mineralization degree of 91 %. Therefore, this study confirmed that the electrochemical process is effective for the degradation of AB10B in water using nanostructured ZnO-TiO2 thin film anodes.