It has been demonstrated that a synthetic solution containing 120 mg L1 of alizarin red can be effectively depolluted by the electro-Fenton process using a gas-diffusion cathode fed with air to electrogenerate hydrogen peroxide. The results of the bulk electrolysis under different experimental conditions showed that the mineralization of alizarin red was primarily affected by the concentration of ferrous ions, because electrogenerated H2O2 alone has limited oxidation power but complete COD and colour removal can be obtained with addition of ferrous ions that promoted the Fenton’s reaction. In the presence of 1.0 mM of Fe2þ, the oxidation rate was also influenced by the current density, the solution pH and temperature, but was almost unaffected by the type of ferrous ions feed, i.e., single step or stepwise addition. The UV–vis
analysis indicated that alizarin red is oxidised firstly to colourless
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