molecules Communication Electrodegradation of Acid Mixture Dye through the Employment of Cu/Fe Macro-Corrosion Galvanic Cell in Na 2 SO 4 Synthetic Wastewater Mateusz Kuczy ´ nski 1 , Mateusz Luba 1 , Tomasz Mikolajczyk 1, * , Boguslaw Piero ˙ zy ´ nski 1, *, Agnieszka Jasiecka-Mikolajczyk 2 , Lech Smoczy ´ nski 1 , Piotr Solowiej 3 and Pawel Wojtacha 4   Citation: Kuczy ´ nski, M.; Luba, M.; Mikolajczyk, T.; Piero˙ zy´ nski, B.; Jasiecka-Mikolajczyk, A.; Smoczy ´ nski, L.; Solowiej, P.; Wojtacha, P. Electrodegradation of Acid Mixture Dye through the Employment of Cu/Fe Macro-Corrosion Galvanic Cell in Na 2 SO 4 Synthetic Wastewater. Molecules 2021, 26, 4580. https:// doi.org/10.3390/molecules26154580 Academic Editors: Wen-Bin Cai and Javier Llanos Received: 23 June 2021 Accepted: 25 July 2021 Published: 29 July 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Chemistry, Faculty of Agriculture and Forestry, University of Warmia and Mazury in Olsztyn, Lódzki Square 4, 10-727 Olsztyn, Poland; mateusz.kuczynski@uwm.edu.pl (M.K.); mateusz.luba@uwm.edu.pl (M.L.); lechs@uwm.edu.pl (L.S.) 2 Department of Pharmacology and Toxicology, Faculty of Veterinary Medicine, University of Warmia and Mazury in Olsztyn, Oczapowskiego 13, 10-719 Olsztyn, Poland; agnieszka.jasiecka@uwm.edu.pl 3 Department of the Electrotechnics, Energetics, Electronics and Automatics, University of Warmia and Mazury in Olsztyn, Oczapowskiego 11, 10-736 Olsztyn, Poland; pit@uwm.edu.pl 4 Department of Industrial and Food Microbiology, Faculty of Food Science, University of Warmia and Mazury in Olsztyn, Cieszy ´ nski Square 1, 10-726, Olsztyn, Poland; pawel.wojtacha@uwm.edu.pl * Correspondence: tomasz.mikolajczyk@uwm.edu.pl (T.M.); bogpierozynski@yahoo.ca (B.P.); Tel.: +48-89-523-4177 (B.P.) Abstract: Traditional wastewater purification processes are based on a combination of physical, chemical, and biological methods; however, typical electrochemical techniques for removing pollu- tants require large amounts of electrical energy. In this study, we report on a process of wastewater purification, through continuous anodic dissolution of iron anode for aerated Cu/Fe galvanic cell in synthetic Na 2 SO 4 wastewater solution. Electrochemical experiments were conducted by means of a laboratory size electrolyzer, where electrocoagulation along with electrooxidation phenomena were examined for wastewater containing Acid Mixture dye. The above was visualized through the employment of electrochemical (cyclic voltammetry and ac impedance spectroscopy techniques) along with instrumental spectroscopy analyses. Keywords: electrocoagulation and electrooxidation; Fe sacrificial anode; galvanic cell; anodic disso- lution; wastewater treatment; acid mixture 1. Introduction Large amounts of different dyes that are present in industrial wastewaters are re- sponsible for serious environmental and health problems [1,2]. Globally, many industries discharge up to 15% of the total dyes used in effluents directly into water bodies. Among various groups of textile dyes, particular attention should be paid to the so-called azo dyes. This specific group of coloring agents is characterized with the presence of one or more azo groups (-N=N-) [3–5]. Large concentrations of azo-type dyes in water have a direct impact on the conditions of all organisms living in a biosystem, which, most importantly, are then transferred to human populations. Various studies conducted in recent years have confirmed serious toxicity, as well as mutagenic and carcinogenic effects of some azo dyes, including their metabolites [6–10]. The above, combined with severe environmental pollu- tions, have led scientists to consider the development of novel, more efficient treatment methods for the dye-based industrial wastewaters. Dc-powered electrochemical methods have widely been examined and utilized for the remediation of dye-polluted wastewaters. These methods are of significant interest as they combine three parallel processes, namely electrocoagulation, electrooxidation and electroflotation [11–13]. Numerous scientific studies have reported total decolorization of Molecules 2021, 26, 4580. https://doi.org/10.3390/molecules26154580 https://www.mdpi.com/journal/molecules