Contents lists available at ScienceDirect Journal of Water Process Engineering journal homepage: www.elsevier.com/locate/jwpe Oxidative degradation of Acid Blue 111 by electro-assisted Fenton process Stevan Lj. Stupar a , Branimir N. Grgur a , Marina M. Radišić b , Antonije E. Onjia a , Negovan D. Ivanković c , Anđelka V. Tomašević d , Dušan Ž. Mijin a, * a Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11020 Belgrade, Serbia b Innovation Center, Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11120 Belgrade, Serbia c Military Academy, University of Defense, Generala Pavla Jurišića Šturma 33, 11000 Belgrade, Serbia d Institute of Pesticides and Environmental Protection, Banatska 31b, P.O. Box 163, 11080 Belgrade-Zemun, Serbia ARTICLE INFO Keywords: Advanced oxidation process LC–MS GC–MS Mineralization Phytotoxicity ABSTRACT The degradation of Acid Blue 111 anthraquinone dye has been studied by the simple electro-assisted Fenton process and the obtained results were compared to the Fenton process. Ferrous sulphate and hydrogen peroxide were used and in the electro-assisted Fenton process IrOx electrode was used as the anode. The influence of hydrogen peroxide and ferrous ion concentration, as well as pH on the processes was investigated. A second- order kinetic was established and rate constants were determined. The degradation was followed by ultraviolet- visible spectroscopy, gas and liquid chromatography-mass spectrometry analysis. Mineralization of Acid Blue 111 was confirmed by total organic carbon analysis and ion chromatography analysis. Efficiency and energy consumption of the processes were calculated. Also, phytotoxicity was studied using the Mung bean seeds. According to the obtained results, the simple electro-assisted Fenton process was much efficient in the de- gradation of Acid Blue 111 dye than the Fenton process. 1. Introduction In recent years, our civilization is turning towards maintaining a healthy and clean environment, and one way to achieve that goal is through the preservation of waterways. The wastewaters from the textile industry contain many hazardous substances which have carci- nogenic and mutagenic effects on living organisms [1–4]. The release of dye molecules into unpolluted waterways interrupts the penetration of sunlight necessary for photosynthesis of the plants, which initiate dis- order in the waterway ecosystem. Textile wastewaters may be highly colored, with a large amount of suspended particles, high pH, high values of wastewater parameters [3,5,6]. Synthetic dyes (and pigments) could be classified according to their structure or their application. When the structure is concerned, azo dyes and pigments represent the largest group, followed by an- thraquinone colorants. Anthraquinone dyes and pigments are based on quinines and represents 15 % of all colorants [7]. Anthraquinone dyes are commonly used for dyeing polymeric and cotton fibers [2]. The Acid Blue 111 (Fig. S1, Supplementary Material, C 31 H 25 N 2 NaO 7 S, AB111) dye contains chromophore groups and has an important place in the textile industry. High toxicity textile wastewater inhibits biolo- gical wastewater treatment steps [6]. In recent years, many environmentally-friendly technologies were developed for dye removal: advanced oxidation processes (AOPs) [8], adsorption [9,72], electro- chemical oxidation processes [10]. AOPs are methods that remove persistent harmful organic substances from water or soil systems using powerful oxidizing agents. The oxidizing agents (usually hydroxyl ra- dical, • OH), which participate in degradation reactions, can be obtained by chemical (e.g. Fenton, ozonolysis), electrochemical (e.g. electro- Fenton) and photochemical (e.g. photo-Fenton, photocatalytic de- gradation, ultraviolet photolysis) methods etc. [11–17]. Fenton and other Fenton processes can be used for the degradation of different organic pollutants, including textile dyes, and encompass the hydrogen peroxide reaction with iron ions to form reactive hydroxyl radicals (value of oxidation potential is 2.80 V) in order to oxidize these compounds [18]. It is the most important for these AOPs to find optimal conditions, such as the appropriate initial concentration of hydrogen peroxide, iron ions, pollutants and proper pH value [15,19–21]. The Fenton process is the simplest process based on direct contact between peroxides and metal ions in the absence of light (Eq. 1) [22]. The following Eq.s (1–4) provide the degradation mechanism [23] where RH is the organic pollutant: + → + + + + Fe HO Fe OH OH 2 2 2 3 – • (1) https://doi.org/10.1016/j.jwpe.2020.101394 Received 8 November 2019; Received in revised form 18 May 2020; Accepted 22 May 2020 ⁎ Corresponding author. E-mail address: kavur@tmf.bg.ac.rs (D.Ž. Mijin). Journal of Water Process Engineering 36 (2020) 101394 2214-7144/ © 2020 Elsevier Ltd. All rights reserved. T