Electro-oxidative decolorization and treatment of model wastewater containing Acid Blue 80 on boron doped diamond and platinum anodes

Abstract

This paper aims to study the decolorization and degradation of textile dye Acid Blue 80 using indirect electrochemical oxidation on active platinum (Pt) and non-active boron doped diamond (BDD) anodes in the presence and formation of chloride ions. Ultraviolet-visible (UV–VIS) spectroscopy helped to monitor the rate of decolorization in relation to the amount of electrolyte, input voltage as well as current density. The effect of pH on the rate of decolorization was also assessed. Following the decolorization of model wastewater, we monitored the subsequent degradation of Acid Blue 80 by repeatedly measuring the values of total organic carbon (TOC), total nitrogen (TN), chemical oxygen demand (COD) and adsorbable organically bound halogens (AOX). Using liquid chromatography-mass spectrometry (LC-MS), we analyzed the reaction mixture and examined the mechanism of Acid Blue 80 decomposition both with the presence and with the exclusion of chloride ions. In the presence of chloride ions, oxidation was also accompanied by substrate chlorination, along with the formation AOX. Their concentration culminated between 6 and 12 h of electro-oxidation, which was then followed by a decrease in AOX values across the entire pH range of 3.0–11.0. After 24 h, Acid Blue 80 was mineralized by 90% at pH = 3.0 on the BDD anode, coupled with a 99% decrease in COD. Under the same conditions, the Pt anode showed a 94% decrease in COD and 64% in TOC.