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Received Oct 2, 2017; Revised Mar 20, 2018; Accepted Apr 1, 2018
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1. Introduction
The textile industry is one of the greatest generators of liquid effluent pollutants due to the high quantities of water used in the dyeing processes. The chemical composition involves a wide range of pollutants: inorganic compounds, polymers, and organic products [1–3]. Treatment of textile dye effluent is difficult and ineffective with conventional processes because many synthetic dyes are very stable in light and high temperature, and they are also nonbiodegradable. Moreover, partial oxidation or reduction can generate very toxic by-products [4–6].
Advanced oxidation processes (AOPs) have emerged as potentially powerful methods that can transform recalcitrant pollutants into harmless substances. AOPs rely on the generation of very reactive free radicals and very powerful oxidants, such as the hydroxyl radical, HO∙ (redox
The resulting organic radicals, then, react with oxygen to initiate a series of degradative oxidation reactions that lead to products, such as CO2 and H2O [1, 11]. Electrochemical oxidation is carried out by indirect and/or direct anodic reactions in which oxygen is transferred from the solvent (water) to the product to be oxidized [12]. The main characteristic of this treatment is that it uses electrical energy as a vector for environmental decontamination [13]. During direct anodic oxidation, pollutants are initially adsorbed on the surface of the anode, where the anodic electron transfer reaction degrades them [6]. In indirect anodic oxidation, strong oxidants, such as hypochlorite, chlorine, ozone, or hydrogen peroxide, are electrochemically generated.
The pollutants are degraded via the oxidation reactions with these strong oxidants [11]. Boron-doped diamond (BDD) thin films are electrode materials that possess several technologically important characteristics, including an inert surface with low adsorption properties, an acceptable conductivity, and remarkable corrosion stability even in strongly acidic media and extremely high O2