Electrodegradation of Acid Mixture Dye through the Employment Electrooxidation and Lemnoideae in Na2SO4 Synthetic Wastewater

In this study, we report on the effectiveness of electrochemical and biological wastewater treatment for artificially prepared industrial wastewater, comprising small amounts of technologically important dyes, namely Acid Mixture composed of Acid Violet 90 (AV90) and Acid Red 357 (AR357) in Na2SO4 (ESS-electrolyte supporting solution), as well as their impact on the environment, using Lemna minor as a bioindicator. Our study revealed that among the tested dyes, the raw ones (AM in ESS+OM) and those subjected to electrooxidation with the use of an iron anode and a copper cathode [AM(Fe/Cuox) in ESS+OM (OECD medium is a medium recommended by the Organization for Economic Co-operation and Development for Lemna sp. Growth Inhibition Test)] were the most phytotoxic for L. minor. No phytotoxicity was detected for the tested plants in solution after electrooxidation with graphite anode and cathode (AM(Cox) in ESS+OM). Quantitative identification of acid mixture removal was carried out by supplementary UPLC/MS-MS (Ultra-Performance Liquid Chromatography/tandem Mass Spectrometry) and UV-VIS (UltraViolet-Visible spectroscopy) instrumental analysis. The final removal after electrochemical and biological treatment of AV90 and AR357 dye components was 98 and over 99%, respectively. The results suggest that it may be a suitable replacement/addition for the generally used wastewater treatment methods.

Automated summary

This study investigates the effectiveness of electrochemical and biological wastewater treatment for artificially prepared industrial wastewater containing important dyes. Lemna minor is used as a bioindicator to assess the environmental impact. The results show that electrooxidation treatment with iron and copper electrodes led to the highest phytotoxicity, while treatment with graphite electrodes showed no toxicity. The removal efficiency of the dye components reached 98% and over 99% after electrochemical and biological treatment, respectively. This suggests that the methods studied may serve as suitable replacements or additions to conventional wastewater treatment methods.