# Electrochemical Degradation of Crystal Violet Using Ti/Pt/SnO\({}_{2}\) Electrode
## 1 Introduction
[32] compared the COD abatement and color removal for direct and indirect electrolysis of a methylene blue solution. It appeared that indirect electrolysis facilitates faster mineralization and discoloration of the solution. This is due to the strong bleaching properties of active chlorine and the indirect electrolysis allows to overcome the mass transfer limitations. The mechanism of electrooxidation depends mainly on the electrocatalytic properties of the anodic material. As a matter of fact, since the refractory compounds oxidize at high potentials, an anode with a high-oxygen overpotential is required. Studies on electrochemical processes by oxidation for water treatment began in the 1970s. Progress was made thanks to the development of new electrode materials. Among electrode materials, platinum used as reference has the advantage to be stable, fairly available, genuine without requiring further processing. However, this material has a low efficiency in anodic oxidation and expensive. Boron doped diamond (BDD) has appeared with growing interest over the last 30 years. As a matter of fact, BDD anodes show unique properties: a high electrochemical window, excellent electrochemical stability, and chemical inertness in acid and caustic media. BDD electrodes allow the complete removal of the organic matter (mineralization) to be envisaged. However, the high manufacturing and operating costs of the material due to high energy consumption limit the development of this material on an industrial scale. Metal oxides and in particular the dimensionally stable anodes, DSA\({}^{\circledR}\), which were discovered in the 1980s are alternatives [33; 34; 35]. Lead dioxide has a high oxygen evolution overpotential. This material is easy to elaborate, cheap and available. However, lead ions may be released into the solution [32]. Tin dioxide has the same advantages, including high oxygen evolution potential, ease of preparation and low cost and the absence of heavy metal contamination [36; 37]. However, the application of tin dioxide anodes can be limited by major problems such as their very low stability (the operational life is generally less than 8 h), which makes these electrodes uncompetitive for applications [38]. Nowadays, in order to extend the electrode life, researchers usually doped noble metal oxides (with Pt, Ru or Ir), which have high corrosion resistance and stability, into the anodic coating of the titanium substrate [39]. In our laboratory, the same lead dioxide anode doped with Pt was used for previous numerous studies without decreasing performances. For each case this electrode showed high efficiencies in organic removal. Among them, [PERSON] et al., used tin oxide to treat oil mill wastewater (OMW), 96% decolourisation and 73% COD reduction were reached [40]. Other works were carried out by [PERSON] et al., the treatment of methylene blue, a 100% removal of colour and a percentage of 80.9% of COD were observed the treatment of Thiabendazole fungicide with a 73% COD removal [41]. The main objective of the work carried out within the framework of this project, is to use an electrode based on Ti/Pt/SnO\({}_{2}\) in view of its application for the depollution of organic effluent including dye: violet crystal (CV). This study will first define the suitable operating conditions for the treatment of effluents in order to obtain decolorization and COD abatement. For this purpose, several operating parameters will be considered such as the nature and concentration of electrolyte, the initial pH, the applied intensity and the initial CV concentration. Then, the energy cost will be evaluated and compared to other studies which were performed using high oxygen overpotential materials for dye treatment.