Discoloration of azo dye Brown HT using different advanced oxidation processes.

In this study, known combinations of Advanced Oxidation Processes (AOPs, namely Electro-Fenton (EF), Photo-Electro-Fenton (PEF), Electro-Oxidation (EO), and EO/Ozone (O) were compared for the discoloration of tannery industry azo dye Brown HT (BHT). The different AOPs were tested in a 0.160 L batch electrochemical stirred thank reactor using Boron Doped Diamond (BDD) electrodes. The influence of parameters such as the current density (j) and the initial BHT concentration were to exanimated on the efficiency of all the tested processes. The oxidation tendency of EF, and PEF were compared with those of EO and O, based on their efficiency for BHT discoloration, which resulted as PEF > EF > EO > O. The AOPs showing the best oxidation performance was PEF which, using NaSO (0.05 M) electrolyte solution and Fe (0.5 mM), pH 3.0, j = 71 mA cm, and 500 rpm process, achieved 100% discoloration and 80% chemical oxygen demand (COD) abatement after 60 min of treatment for two initial BHT concentrations (50 and 80 mg L). The process accounted for a current efficiency of 30% and energy consumption 2.25 kWh (g COD) through the discoloration test. The azo dye gradually degraded, yielding non-toxic oxalic, oxamic, and glyoxylic acid, whose Fe(III) complexes were quickly photolyzed.