Electro-Fenton method for the removal of methyl red in an efficient electrochemical system

To promote treatment efficiency, an efficient undivided electrochemical system using a graphite-polytetrafluoroethylene (PTFE) cathode with high production rate of hydrogen peroxide and current efficiency under wider pH ranges was applied to the electro-Fenton oxidation of a model azo dye, methyl red. The influences of operating parameters including electrolyte Na2SO4 concentration, cathodic potential, pH, Fe2+ concentration and initial methyl red concentration were investigated. At the conditions of cathodic potential of −0.55 V versus SCE, pH 3, Fe2+ concentration of 0.2 M, methyl red of initial concentration of 100 mg/L could be removed 80% in 20 min. Due to the consumption of ferrous ion and formation of hard-to-treat intermediates during treatment, the removal of methyl red was found degraded at two different stages, and the second stage was much slower than the first one.