How Ruthenium Oxide Titanium Anode Performs in Electrochemical Oxidation Paper Wastewater?

How Ruthenium Oxide Titanium Anode Performs in Electrochemical Oxidation Paper Wastewater?

Wastewater from the paper industry presents an environmental pollution problem because the high quantity of water used in the process results in large amounts of wastewater with a high organic load. A variety of studies have examined treatments based on biological processes (aerobic, anaerobic, algal) or physicochemical approaches (coagulation–flocculation, ozonation, photocatalysis, electrochemistry).

The electrochemical oxidation of organic matter has provided favorable results in the treatment of wastewater from different industries. In the paper industry, this process has been applied using graphite, lead anodes, or dimensionally stable anode-type electrodes (DSA). These electrode materials can reduce the COD, color, and polyphenols from the paper industry wastewater. The effectiveness of the electrochemical oxidation process applied to organic matter depends essentially on the electrocatalytic activity of the electrode material that constitutes the anode; therefore, the appropriate selection of the anode can increase the removal of organic matter with high efficiency.

Considering the importance of the anode composition on the electrochemical oxidation process, Scientists compared the effectiveness of the oxidation processes in paper industry wastewater treatment using two types of dimensionally stable anodes with compositions based on Ru oxide or Ru-Ir-Co oxides supported on Ti. These electrodes were represented as electrode 1 (E1), for Ti/RuO2, and electrode 2 (E2), for Ti/RuIrCo. The effectiveness of the anodes in removing organic matter from paper industry wastewater revealed that RuO2 displayed unique electrocatalytic properties in the presence of Ir and Co. The effectiveness of the electrochemical treatment of wastewater using both anodes was evaluated by measuring the removal of COD, color, and polyphenols, and by using UV-Vis spectroscopy.

The electrochemical oxidation of paper industry wastewater was studied using the dimensionally stable anodes Ti/RuO2 and Ti/RuIrCo. Both anodes reduced the COD content, color, and polyphenol content; however, the removal capacity depended on the electrode material, the presence of NaCl as a supporting electrolyte, and the electrolysis time. In the absence of NaCl, the Ti/RuO2 anode provided the greatest reductions in COD, color, and polyphenols. The maximum COD removal values were 55% at the Ti/RuO2 anode and 36% at the Ti/RuIrCo anode. The electrochemical oxidation process appeared to occur through a mechanism that was directly limited by the oxygen evolution reaction, which occurred simultaneously at the electrode. In the presence of NaCl, both anodes provided greater COD, color, and polyphenol removal at relatively short electrolysis times. In this case, the Ti/RuIrCo anode performed best in COD removal (80%). Under these conditions, the electrochemical oxidation process appeared to occur through both mechanisms (direct and indirect); however, the indirect mechanism was favored by the Ti/RuIrCo anode over the Ti/RuO2, which could explain the fact that a greater COD removal occurred in the presence of the Ti/RuIrCo anode.