Effect of Persulfate Activation by Electrogenerated H2O2 and Anodic Oxidation on the Color Removal of Dye Solutions at Pt and BDD Anodes.

In this study, tartrazine solutions were oxidized using innovative electrochemical advanced oxidation processes (EAOPs) that combined persulfate (PS) activation with electrogenerated H2O2, cathodic reduction and anodic oxidation at Pt and BDD anodes, and graphite cathode in an undivided stirred reactor. For the Pt anode, SO4·- was generated from a reduction reaction at the cathode and a reaction between the PS and electrogenerated H2O2. For the BDD anode, SO4·- was generated from a reduction reaction at the cathode, an oxidation reaction at the anode, and a reaction between PS and electrogenerated H2O2. Among these activation methods, the activation efficiency of PS by electrogenerated H2O2 is much better than other methods. The effects of PS concentration up to 36 mM, applied current density between 6 to 15 mA cm-2, and temperatures between 25 to 45 °C were investigated. For the electro-Fenton process with Pt anode (Pt-H2O2/PS process), the best result for oxidizing 250 mg L-1 tartrazine solution was obtained with 37.5 mM Na2SO4 + 9.0 mM Na2S2O8, applied current density at 12 mA cm-2 and 45 °C, acquiring total color removal after 30 min reaction. For the electro-Fenton process with BDD anode (BDD-H2O2/PS process), the best result for oxidizing 250 mg L-1 tartrazine solution was obtained with 25 mM Na2SO4 + 18 mM Na2S2O8, applied current density at 12 mA cm-2 and 45 °C, yielding 100% color removal after 30 min reaction. The main oxidizing agents are SO4·- and OH· in the anodic oxidation process with PS and the electro-Fenton process with PS. It is concluded that the additions of PS tremendously improve the oxidation power of electro-Fenton processes with PS, especially the Pt-H2O2/PS process.