Electrochemical Oxidation of the Xanthene Dye Rhodamine 6G by Electrochemical Advanced Oxidation Using Pt and BDD Anodes

Nadjia      Khalfaoui; Hocine      Boutoumi; Hussein      Khalaf; Nihal      Oturan; Mehmet      A. Oturan

doi:10.2174/138527212803532459

Abstract

Aqueous solutions of Rhodamine 6G (R6G), one of the more used xanthene dye, were treated by hydroxyl radicals ( · OH) electrocatalytically generated through the electro-Fenton process, a powerful and environmentally friendly electrochemical method. Platinum (Pt) or boron-doped diamond (BDD) anodes were used with a carbon-felt cathode. The effect of anode nature and applied current on the degradation and mineralization kinetics was investigated. The applied current value of 500 mA was found as optimum operating parameter for both anodes under our operating conditions. Kinetic data of R6G disappearance follow the pseudo-first order reaction decay process. The rate constant of the oxidation reaction between R6G and hydroxyl radicals was determined by competition kinetics method and found as 3.41 x 109 M-1 s-1. The mineralization efficiency was found very high with both anodes reaching 99% and 98% for BDD and Pt respectively at 500 mA. Oxalic acid was identified as ultimate end-product before complete mineralization. The two secondary amine groups of R6G were converted mainly into NH4 + ions whereas NO3 - ions are released to the solution at relatively low proportion.

Keywords: Rhodamine 6G, Advanced oxidation process, Hydroxyl radical, Boron-doped diamond, Electro-Fenton process, Mineralization, xanthene dye, carcinogenic, anaerobic, recalcitrant.