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    A comparative study on decolorization of AB172 and BR46 textile dyes by electrochemical processes: multivariate experimental design
    (Wiley, 2025) Ilhan, Hilal; Can, Orhan Taner; Guvenc, Senem Yazici; Can-Guven, Emine; Varank, Gamze
    BACKGROUND Textile dyes, used for coloring fabrics, cause environmental challenges because approximately 30% of the applied dye may enter the wastewater without being treated. This wastewater has intense color, variable pH, and salt content. Limited biodegradability of dyes due to their complex polymer structures necessitates advanced treatment. This study investigated the decolorization of dyeing wastewater by electrocoagulation (EC) and electrooxidation (EO) methods, which are common techniques of electrochemical advanced oxidation processes. Box-Behnken design was applied to experimental design in the determination of the maximum removal efficiency. Initial pH, current density (CD), and reaction time (RT) were chosen as independent variables, and the removal efficiency of Acid Black 172 (AB172) and Basic Red 46 (BR46) dyestuffs was selected as model responses.RESULTS Higher BR46 dyestuff removal efficiency was obtained by the EO process using a Ti:RuO2:IrO2 electrode, and higher AB172 dyestuff removal efficiency was obtained by the EC process using an Al electrode. Under optimum conditions, the highest removal efficiencies based on dyestuff were 93.4% with the EC process for AB172 dyestuff (initial pH 5.63; CD 0.07 mA cm-2; RT 13.1 min) and 94.0% for BR46 dyestuff with the EO process (initial pH 4.61; CD 2.89 mA cm-2; RT 72.6 min).CONCLUSION The study suggests that electrochemical methods hold promise for treating dyeing wastewater, providing water recovery and appropriate modeling. Both EC and EO processes, when optimized via Box-Behnken design, offer high dye removal efficiencies with low energy requirements, highlighting their suitability for sustainable textile wastewater treatment. (c) 2025 Society of Chemical Industry (SCI).
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    Advanced electrocoagulation using aluminum electrodes supported by persulfate for the treatment of a high-strength wastewater
    (Elsevier, 2023) Yokus, Senem; Bilgin, Oyku Nur; Yilmaz, Ezgi Unal; Gundogdu, Hilal; Guvenc, Senem Yazici; Can-Guven, Emine; Varank, Gamze
    In this study, the treatment of leachate nanofiltration (NF) concentrate, which is high -strength wastewater, by advanced electrocoagulation (EC) was investigated. The EC pro-cess, in which aluminum electrodes were used, was enhanced by persulfate (PS) addition (EC-PS). First, the control experiments were conducted then the operating parameters of the process were optimized by the Box-Behnken design. Process variables were PS dose, applied current, initial pH, and reaction time while chemical oxygen demand (COD), total organic carbon (TOC), UV254, and color removal were the system responses. COD, TOC, UV254, and color removal efficiencies by the validation studies performed under optimized conditions (PS dose: 0.590 g/L; applied current: 0.710 A; initial pH: 5, and reaction time: 31.4 min) were 62.6%, 54.3%, 74.2%, and 88.0%, respectively. Based on the degree of effect on COD and TOC removal, statistical analysis parameters can be listed as linear, quad-ratic, and interactive from higher to lower one. The linear parameters can be listed as initial pH, applied current, reaction time, and PS dose according to the level of their effect on removal efficiencies. Quenching experiments showed that sulfate and hydroxyl radi-cals work together in the process while hydroxyl radicals were more effective. The specific energy consumption and total cost of the process under optimized operating conditions were 1.90 kWh/kg COD and 1.40 $/m3 respectively. By obtaining the spectrum of the sludge formed under optimum process conditions by Fourier Transform Infrared Spectroscopy analysis, the characteristics of the sludge were determined and Al hydroxides and hy-drocarbons were present in the sludge. (c) 2023 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.
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    Biodegradability enhancement of landfill leachate nanofiltration concentrate using sequential and combined electrochemical processes
    (Elsevier, 2025) Yucel, Esra; Ozen, Irem; Cene, Gulay Arslan; Ilhan, Hilal; Guvenc, Senem Yazici; Can-Guven, Emine; Demir, Ahmet
    In this study, the treatment of landfill leachate nanofiltration concentrate (LNFC) was investigated using sequential (two distinct stages, one following the other) and combined (two mechanisms operating simultaneously in a single reactor) electrochemical processes. In the first stage, initial pH, applied current, and reaction time were optimized for individual processes: electro-oxidation (EO), peroxi-coagulation (PC), and electrochemical-peroxidation (EP). In the second stage, sequential (EO-PC, PC-EO, EO-EP, EP-EO) and combined (EO/PC, EO/EP) processes were applied with the optimal conditions determined in the first stage. Under optimum conditions (pH 5; applied current 1 A; reaction time 60 min), chemical oxygen demand (COD) removal efficiencies of 38.9 %, 42.1 %, and 53.1 % were obtained for the EO, PC, and EP processes, respectively. Enhanced COD removal was obtained by sequential processes, yielding removal rates of 65.6 % for EO-PC, 71.1 % for PC-EO, 78.3 % for EO-EP, and 83.6 % for EP-EO. The highest efficiencies were observed in the combined systems, with COD removals of 76.4 % for EO/PC and 89.1 % for EO/EP. The lowest specific energy consumption (SEC) was calculated as 31.2 kWh/kg COD for EP among the single processes, 41.0 kWh/kg COD for EP-EO among the sequential processes, and 47.5 kWh/kg COD for EO/EP among the combined processes. These findings suggest that EP-based systems require less energy than EO-based systems. The EO/EP process can be proposed as an alternative treatment for LNFC due to its compliance with the discharge standards (500 mg/L for COD for leachate) specified in the Water Pollution Control Regulation of T & uuml;rkiye and its relatively low SEC.