Degradation of Acid Violet 19 textile dye by electro-peroxone in a laboratory flow plant

Abstract

This paper deals with the degradation of Acid Violet 19 (AV19) textile dye by the electro-peroxone (E-peroxone) process in a laboratory flow plant using a filter press cell fitted with a 3D gas diffusion electrode (3D GDE) containing a graphite felt positioned on carbon-cloth PTFE as cathode, and a Ti|IrSnSb-oxides plate as anode. H2O2 was formed by the oxygen reduction reaction (ORR) in the cathode; the air was supplied by an external compressor. The O3 produced externally by an ozonator was added in the pipeline at the outlet of the electrolyzer to promote the reaction between the H2O2 and O3 to produce OH, which is the responsible for the mineralization of the dye. The effect of electrolyte flow rate (Q), current density (j), and initial concentration of AV19 dye on its degradation was addressed. The best electrolysis in a solution containing 40 mg TOC L−1, 0.05 M Na2SO4, at pH 3, was obtained at j = 20 mA cm−2, Q = 2.0 L min−1, using a pressure of the air fed to the 3D GDE of PGDE = 3 psi, and an ozone inlet mass flow rate of F03 = 14.5 mg L−1, achieving 100% discoloration, 60% mineralization, with mineralization current efficiency and energy consumption of 36% and 0.085 kWh(gTOC)−1. The degradation of AV19 dye was also performed by anodic oxidation plus H2O2 electrogenerated (AO-H2O2) and ozonation. The oxidation power was AO-H2O2 < ozonation < E-peroxone. Three carboxylic acids were quantified by chromatography as oxidation end products.