(200e) Comparison of Electrodes for Application in Anodic Oxidation of Wastewater Constituents

Zelenka, J., Graz University of Technology
Gangl, W., University of Technology Graz, Department of Chemical Engineering and Environmental Technology
Letonja, P., Graz University of Technology
Siebenhofer, M., Graz University of Technology
Marr, R., Graz University of Technology

Since new electrode materials such as glassy carbon, several metal oxides and diamond doped titanium electrodes have established in industrial application and research electrochemical oxidation in synthesis as well as wastewater treatment offer several new applications for EAOPs (Electrochemical Advanced Oxidation Processes). For both applications, anodic synthesis as well as wastewater treatment, detailed knowledge of the operation set up and the operation conditions is needed to enable feasible operation. Target of this project has been the comparison of iridium oxide doped DSA, glassy carbon and diamond electrodes in oxidative wastewater treatment. Investigation has considered the correlation of current density and anode potential for specified electrolyte composition and temperature of operation. Investigation has been carried out for open cell as well as membrane cell applications. Figure 1 shows a representative current density/potential graph for investigation of an iridium oxide doped titanium anode. The experiment was carried out at 296 K; sodium sulphate concentration was 0.05 M/l and EDTA concentration was 1.34 mM/l. Basically stable operation conditions in practical application are expected from this detailed analysis of operation. Investigation has therefore considered the current/ potential characteristic of the basic electrolyte as well as different states of conversion. Investigation has been carried out with the model substance ethylenediamine-tetraacetic acid (EDTA) and the conductance electrolyte sodium sulphate. EDTA has been selected because of its broad application and its properties. Sodium sulphate has been chosen to avoid unwanted interaction of the basic electrolyte and the anode. Under anodic charge EDTA can undergo cleavage as well as oxidation. Rate and efficiency of both routes strongly depend on the current density and the corresponding anode potential. Cleavage has been analysed through the complexation properties of the synthetic effluent. Oxidation has been quantified through TOC-analysis. Based on the current/potential correlation and batch conversion tests in bench scale the specific energy consumption has been determined for electrode comparison.

Figure 1: Current density vs. anode potential of an iridium oxide doped titanium anode at 296 K, electrolyte concentration 0.05M/l Na2SO4 and 1.34 mM/l EDTA


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