Dimensionally Stable Anode Electrode Research Articles

Coal to Clean: Comparing Advanced Electrodes for Desulfurization and Copper Recovery

This study explores the electrochemical desulfurization of coal and the recovery of copper (Cu) using dimensionally stable anode (DSA) electrodes. Background: The research addresses the need for effective sulfur removal from coal to reduce emissions. Methods: Electrochemical desulfurization was conducted using DSA and graphite electrodes, evaluating parameters like activation energy, desulfurization rate, and energy consumption. Cyclic voltammetry and linear sweep voltammetry were used to study the electrochemical properties. Results: The DSA electrode demonstrated superior performance with higher desulfurization rates, lower activation energy, and better response to temperature increases compared to the graphite electrode. Optimal desulfurization was achieved at 50 °C with the DSA electrode, balancing efficiency and energy consumption. Copper recovery from the solution post-desulfurization was effective, with an 86.34% recovery rate at −0.15 V vs. (Ag|AgCl). The energy consumption for the Cu recovery was calculated to be 10.56 J, and the total cost for recovering 1 ton of Cu was approximately 781.20 €. Conclusions: The study highlights the advantages of DSA electrodes for efficient sulfur removal and metal recovery, promoting cleaner energy production and environmental sustainability. Future research should focus on optimizing electrochemical conditions and scaling up the process for industrial applications.

Application and optimization of electro-Fenton technology in advanced treatment of petrochemical industry wastewater

Within this research endeavor, a refined electric-Fenton remediation protocol was put forth for the enhanced reconditioning of intensely polluted organic effluents originating from the petrochemical sector. Using DSA (Dimensionally Stable Anode) electrode material and ultraviolet (UV) catalysis, the wastewater treatment efficiency and the ability to degrade refractory organic compounds were significantly improved. By optimizing the reaction parameters, the mineralization speed and treatment efficiency of organic matter are significantly improved, the use of H2O2 is reduced, and the cost of chemicals and energy consumption are reduced. At the same time, the technology avoids the use of a large number of harmful chemicals and mitigates the peril of subsequent contamination, thus rendering it appropriate for a spectrum of petrochemical effluents. Moreover, it exhibits efficacious abatement on diverse categories of organic contaminants.

Electrochemical degradation of reactive dyes mixture over DSA electrodes: A sustainable approach

Wastewater treatment is one of the major concerns of industries and researchers. Effluents containing reactive dyes which are harmful to human health and ecological systems are the most difficult to treat. Among all treatments, electrochemical oxidation is deemed to be one of the cheapest and most effective treatments. Keeping the advancement in the aforesaid treatment method, this paper focuses on the selection of various substrates for preparation of the electrode material which decidedly have a significant effect on the efficacy of the electrochemical degradation of organic pollutants. Also, the need for an economic and stable electrode has led to the requirement to develop or select a novel anode material with enhanced electrocatalytic properties. Addressing the concern this paper highlights the preparation of Dimensionally Stable Anode (DSA). Herein the comparisons of various DSA electrodes to degrade organic pollutants, their synthesis methods, characterization arereviewed.. Factors influencing electrochemical oxidation efficiencies such as pH, temperature, current density, and supporting electrolytes are also studied. The challenges and possible improvements in DSA electrodes are also included herewith. This work wishes to focus on the synthesis of modified DSA electrodes to degrade reactive dye mixtures.

Using Ti/Ti0.7Ru0.3O2 anode-type with a Flow Cell System for the Electrochemical Treatment of a Tannery Wastewater

ABSTRACT The electrochemical oxidation of a real wastewater discharged by the baths of “Dar Dbagh” tannery (DDT) in Fez city (Morocco) was performed using Ti/Ti0.7Ru0.3O2 anode (a dimensionally stable anode (DSA)-type electrode) underflow condition. The effect of different operational parameters, namely chloride ions concentration, electrolysis time, current density, initial pH, and temperature has been studied in detail. The discoloration and chemical oxygen demand (COD) removal have been taken as the key experimental indicators to monitor the electrochemical treatment process of DDT wastewater. The obtained results have shown that the best degradation rates (i.e., 100% and 56% of de-colorization and COD removal, respectively) were accomplished under acidic conditions at 20 mA cm−2 as a current density in the presence of 0.033 M Na2SO4 + 0.800 M NaCl as supporting electrolyte at room temperature. The maximum reduction of the effluent COD attained using Ti/Ti0.7Ru0.3O2 anode consuming 39.24 kWh per m3 clearly shows that DSA electrodes could be a good alternative for the remediation of DDT effluents.

RuO2/IrO2 nanoparticles decorated TiO2 nanotube arrays for improved activity towards chlorine evolution reaction

Dimensionally stable anodes (DSA) have been extensively employed for industrial chlorine evolution reactions (CER). Many efforts have been made to develop nanostructured DSA electrodes to enhance the stability and catalytic activity of CER. Herein, a composite catalyst composed of RuO2/IrO2 decorated TiO2 nanotube arrays (TiO2 NTAs) was proposed for CER applications. 1D TiO2 NTAs were fabricated by electrochemical anodization. RuO2/IrO2 nanoparticles were embedded in TiO2 NTAs by electrochemical deposition. Catalytic activity of RuO2/IrO2-TiO2 NTAs is superior to most CER materials. At a current density of 50 mA cm−2, the overpotential is 1.115 V (vs. SCE) with a Tafel slope of 33.5 mV dec−1 in 5 M NaCl. The RuO2/IrO2-TiO2 NTAs exhibit good selectivity towards oxygen evolution reaction, with a potential separation of 205 mV at 50 mA cm−2. The RuO2/IrO2-TiO2 NTAs also display excellent stability for CER. Almost no attenuation is observed after 50 h test.

Preparation and Recent Developments of Ti/SnO2-Sb Electrodes

Ti/SnO2-Sb electrode, which is one of the dimensionally stable anode (DSA) electrodes, offers high specific conductivity, excellent electrocatalytic performance, and great chemical stability. For these reasons, Ti/SnO2-Sb electrode has been extensively studied in the fields of wastewater treatment. This review covers essential research work about the advanced oxidation technology and related DSA electrodes. It gives an overview of preparation methods of SnO2 electrodes, including sol-gel method, dip-coating method, electrodeposition method, chemical vapor deposition method, thermal decomposition method, magnetron sputtering method, and hydrothermal method. To extend service life and improve electrocatalytic efficiency, the review provides comprehensive details about the modification technologies of Ti/SnO2-Sb electrode, such as doping modification, composite modification, and structural modification. In addition, the review discusses common problems in industrial applications of Ti/SnO2-Sb electrode and highlights the promising outlook of Ti/SnO2-Sb electrode.

Degradation of thiocyanate by electrochemical oxidation process in coke oven wastewater: Role of operative parameters and mechanistic study

This study presents the removal of thiocyanate (SCN−) from coke oven wastewater by the electrooxidation (EO) process. Initially, the performances boron-doped diamond (BDD) and different DSA (Dimensionally stable anode) electrodes including Ti/IrO2, Ti/IrO2−RuO2, and Ti/IrO2−RuO2−TiO2 in SCN− removal were compared. BDD anode outperformed the Ti−based mixed metal oxide (MMO) anodes achieving 96.51% SCN− removal efficiency. The most favorable conditions for the removal of SCN− using BDD anode were determined as follows: pH = 9, current density = 43.10 A m−2, and the electrolyte concentration (Na2SO4) = 2.5 g L−1. The strong role of ⦁OH in the removal of SCN− was confirmed by the addition of radical quenching agents. The evolution of the intermediates as a result of the EO of SCN− was determined. Under the determined conditions, the EO process could remove 84.13% of SCN− and 94.67% of phenol from a real coke oven wastewater, which was comparable to that of the simulated solution. The electrical energy consumption cost of the process to remove 1 kg of SCN− was calculated as 0.208 US $. Overall, the study showed the EO using BDD anode is a cost-effective method for the removal of SCN− from a coke oven wastewater.

Degradation of oxamic acid using dimensionally stable anodes (DSA) based on a mixture of RuO2 and IrO2 nanoparticles

Dimensionally stable anodes (DSA) have been widely used to degrade organic compounds because these surfaces promote the electrogeneration of active chlorine species in the bulk of the solution, as well as in the vicinity of the anode when NaCl is used as supporting electrolyte. In this work, the nanoparticles synthesis of IrO2 and RuO2 was performed to obtain two types of DSA electrodes named Class I and II to degrade oxamic acid. For Class I and II DSA, the nanoparticles used were synthesized separately and in the same reaction medium, respectively. Electrolysis were carried out in an open cylindrical cell without division at 25 °C, DSAs were used as anodes and a stainless-steel electrode as cathode, both elements have a geometric area of 2.8 cm2 immersed in 0.05 mol L−1 of NaCl or Na2SO4 and a current density of 3 mA cm−2 was applied for 6 h. Active chlorine species generated in the absence of oxamic acid in NaCl were also detected and quantified through ion chromatography. In Na2SO4 there was no degradation of the compound, but in NaCl the oxamic acid concentration reaching 85% with Class I DSA. The same tendency is observed in mineralization, in which Class I DSA allowed reaching a CO2 transformation close to 73%. The difference in the results occurs because with Class I DSA, more hypochlorite is generated than with Class II and therefore there is a larger amount of oxidizing species in the solution that enables the degradation and mineralization of oxamic acid.

Electrodeposited mesh-type dimensionally stable anode for oxygen evolution reaction in acidic and alkaline media

A mesh-type dimensionally stable anode (DSA) consisting of ruthenium and iridium with low catalyst loading was prepared as an oxygen evolution reaction catalyst in acidic and alkaline media. The electrodeposition (ED) conditions, i.e., applied current density and total cycle number, and ED solutions with different precursor ratios of ruthenium to iridium are examined to fabricate various DSAs with a uniform thickness, and the effect of the iridium content on the catalytic activity is investigated. Among various DSA electrodes, the DSA electrode without iridium exhibits the highest activity and stability in the acidic medium owing to the high ratio of ruthenium. Conversely, the DSA electrode obtained using the ED solution with the ratio of 8:2 exhibits the highest performance in the alkaline medium. This is because the DSA electrode without iridium showed low stability, which is attributed to the dissolution of ruthenium oxide in the alkaline medium. In addition, two large-scale DSA electrodes optimized in the acidic and alkaline electrolytes show excellent performance, indicating the feasibility of the application of this electrode in practical electrolysis.

Improving the Stability of DSA Electrodes by the Addition of TiO2 Nanoparticles

Dimensionally stable anodes (DSA) are widely used in water electrolysis, cathodic protection, wastewater treatment, metal electrowinning and chlor-alkali industry. An important parameter of these anodes is their lifetime under harsh anodic conditions. In this work, the incorporation of TiO2 nanoparticles into a thermally prepared IrO2 anode as a way of improving its service lifetime was investigated. The results show that incorporation of up to 25 wt% TiO2 nanoparticles into the coating formed crack-free structure during the thermal decomposition process and thus enhances the service lifetime of modified electrode dramatically by up to 10x compared to the pure IrO2 anode. Importantly, these nanoparticle additions have minimal effect of the anodes performance toward the oxygen evolution reaction. Further addition of TiO2 nanoparticles reduced the lifetime of the anode due to uneven distribution of the active coating over the substrate leading to electrolyte penetration to, and passivation of, the underlying titanium substrate. It is proposed that adding the right quantity of nanoparticles into the IrO2 layer improved the anodes lifetime by minimising electrolyte penetration to the substrate while increasing the mechanical strength of the layer.

Synthesis of Ti|IrO2-SnO2-Sb2O3 electrodes without Chloride Precursors and Their Electrochemical Applications

Electrochemical oxidation depends enormously on the electrode materials used during electrolysis. Dimensionally Stable Anodes (DSA) represent a good option for electrochemical oxidation applied to wastewater treatment due to the ability of generating hydroxyl radicals. These radicals are strong, non-selective oxidizing agents, which are able to react with organic pollutants and mineralize them. However, this kind of electrodes is commonly synthesized from chloride precursors, which represents an environmental problem, because they can form undesirable chlorinated by-products during the electrolysis. Some DSA electrodes such as PbO2, SnO2-Sb2O5 and TiO2 are promising anodes due to their high over-potential for oxygen evolution, which leads to the ability of OH radical production; however, their main drawback is the low chemical stability [1, 2]. This disadvantage prevents their use in environmental applications and causes the search for other materials with better properties. In this work we present the synthesis as well as its electrochemical application of a DSA electrode composed of Ti|IrO2-SnO2-Sb2O3. The purpose is enhancing the chemical stability and prolonging the electrode lifetime. The Pechini concept was used to this material, but with the advantage that no chloride precursors were employed [3]. Cyclic voltammetry (CV), X-ray diffraction (DRX), Energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) were used to characterize the as-prepared electrode. The electrocatalytic properties were evaluated by electrochemical degradation of tartrazine in aqueous media as well as dibenzothiophene in organic media. Results showed that noncracked oxide layers were obtained and that the electrode has a great capability for the electrochemical degradation of both molecules. Keywords: DSA electrode, Ti|IrO2-SnO2-Sb2O3, tartrazine, dibenzothiophene X. Chen, G. Chen, Anodic oxidation of dyes at novel Ti/B-diamond electrodes, Chem. Eng. Sci. 58 (2003) 995.X. Chen, G. Chen, F. Gao, P. Yue, High-performance Ti/BDD electrodes for pollutant oxidation, Environ. Sci. Technol. 37 (2003) 5021.M. H. P. Santana, L. M. Da Silva, L. A. De Faria, (2003). Investigation of Surface Properties of Ru-Based Oxide Electrodes Containing Ti, Ce and Nb. Electrochim. Acta, 48 (13), 1885.

A Basic Study on Accelerated Life Test Method and Device of DSA (Dimensionally Stable Anode) Electrode

A Basic Study on Accelerated Life Test Method and Device of DSA (Dimensionally Stable Anode) Electrode

Application of BDD and DSA electrodes for the removal of RB 5 in batch and continuous operation

The experiments on removal of Reactive black 5 (RB 5) dye were performed in batch and continuous operation using boron doped diamond (BDD) and dimensionally stable anode (DSA) electrodes. The electrooxidation of simulated wastewater was carried out in aqueous medium of pH 2 containing 100mg/L RB 5 on Si/BDD and Nb/BDD electrodes. For batch degradation studies of RB 5, 50mA/cm2 current density was applied in the presence of 4g/L NaCl as supporting electrolyte. The electrolysis was performed on both the BDD electrodes with each electrode having effective area of 25cm2. As a result of batch operation, almost 99% decolourization and 90% chemical oxygen demand (COD) removal was observed after 30min of electrolysis due to electrooxidation on non-active anodes.Further, an attempt was made to degrade RB 5 using three tanks in series in continuous operation under identical operating conditions of batch process. For this operation, two Ti/PtOx-RuO2-SnO2-Sb2O5 electrodes were equipped in first two tanks while third tank was operated with Si/BDD and Nb/BDD one after another. The effects of constant flow rate of 30mL/min were evaluated for removal of colour, COD and total organic carbon (TOC) from aqueous solution of RB 5 azo dye. As a consequence of electrolysis, 99% colour removal, 95% COD removal and more than 70% TOC removal were observed. Characterization of the electrodes were carried out for surface morphology analysis by scanning electron microscopy (SEM),surface structure analysis was performed by x-ray diffraction (XRD) while electrochemical behaviour was observed by cyclic voltammetry techniques.

Inactivation, lysis and degradation by-products of Saccharomyces cerevisiae by electrooxidation using DSA.

The yeast Saccharomyces cerevisiae, a microorganism with cell walls resistant to many types of treatments, was chosen as a model to study electrochemical disinfection process using dimensionally stable anodes (DSA). DSA electrodes with nominal composition of Ti/RuO2TiO2 and Ti/RuO2TiO2IrO2 were evaluated in 0.05molL-1 Na2SO4 containing yeast. The results showed inactivation about of 100% of the microorganisms at Ti/RuO2TiO2 by applying 20 and 60mAcm-2 after 120min of electrolysis, while a complete inactivation at Ti/RuO2IrO2TiO2 electrode was achieved after 180min at 60mAcm-2. When chloride ions were added in the electrolyte solution, 100% of the yeast was inactivated at 20mAcm-2 after 120min of electrolysis, independent of the anode used. In the absence of chloride, the energy consumption (EC) was of 34.80kWhm-3, at 20mAcm-2 by using Ti/RuO2TiO2 anode. Meanwhile, in the presence of chloride, EC was reduced, requiring 30.24 and 30.99kWhm-3 at 20mAcm-2, for Ti/RuO2TiO2 and Ti/RuO2IrO2TiO2 electrodes, respectively, The best performance for cell lysis was obtained in the presence of chloride with EC of 88.80kWhm-3 (Ti/RuO2TiO2) and 91.85kWhm-3 (Ti/RuO2IrO2TiO2) to remove, respectively, 92 and 95% of density yeast. The results clearly showed that yeast, as a model adopted, was efficiently inactivated and lysed by electrolysis disinfection using DSA-type electrodes.

TiO2 nanotube arrays based DSA electrode and application in treating dye wastewater

Dimensionally stable anode (DSA) of antimony-doped tin dioxide electrode based on TiO2-nanotube arrays (NTs) has been successfully fabricated through thermal decomposition. The surface morphology and composition of the electrodes were characterized by using scanning electron microscopy and X-ray diffraction. Methyl orange (MO) was used as a model pollutant to investigate the electrochemical properties of these two electrodes. The optimized anodic oxidation voltage and time for TiO2-nanotubes array based DSA electrode is 60 V and 10 min, respectively. The results show that Ti/TiO2–NTs/Sb–SnO2 electrode has an increase of 100 mV in oxygen evolution overpotential and the service life is 56% longer than that of the traditional DSA electrode. Under the optimum conditions, MO solution decolorization rate and TOC removal rate reached approximately 100 and 80%, respectively. Study suggested that the as-prepared Ti/TiO2–NTs/Sb–SnO2 DSA electrode exhibits high activity for degradation of organic pollutant with high concentration.

Proposal for Deposition Mechanism of Electrochemical-Constructed IrO2-Ta2O5|Ti Electrodes

Dimensionally Stable Anodes (DSA) were invented by Henri Beer in 1965 under the brand name DSA. These electrodes are characterized by their shape and structural integrity and included a catalytic coating with corrosion resistance properties [1-2]. These materials are very appealing for many applications because of their high chemical and electrochemical stability, low cost and exceptional ability to catalyze electrochemical reactions [3]. Also, DSA electrodes are able to produce hydroxyl radicals (·OH) at the interface level, which may have a large number of applications [4-5]. DSA electrodes usually employ titanium as a support material and can be coated with oxides of transition metals. For this investigation, the electrodes were coated with IrO2 and Ta2O5 due to their excellent performance.There are many investigations focused on the applications of these types of electrodes, but it is necessary to increase the information related to titanium pretreatment and the mechanism of iridium and tantalum deposition in order to thoroughly understand the structure of such electrodes [6-9]. Studies focused on coating quality enhancement are important in order to increase their performance, catalytic properties and stability against corrosion. A crucial factor for DSA synthesis is the titanium pretreatment, which aims to increase the electrode area and clean it in order to facilitate the deposition of transition metals. For this investigation, titanium electrodes were sandblasted and etched with oxalic acid [1-2]. Also, there are factors related to the deposition, such as the concentration of salts in the precursor solution and its subsequent thermal treatment. The main goal of this research is to modify titanium electrodes with IrO2 and Ta2O5 by electrochemical deposition and study the changes in the electrode surface during the different stages of pretreatment and modification, in order understand the deposition mechanism and to improve their catalytic activity in the generation of hydroxyl radicals at the interface level [3]. The modified surfaces were characterized by Cyclic Voltammetry (CV), Diffraction X-Ray (DRX), perfilometry, Scanning Emission Microscopy (SEM) and Energy Dispersive X-Ray spectroscopy (EDX). Additionally, the production of ·OH was monitored by UV-Vis spectrophotometry. References P. Duby, The history of progress in dimensionally stable anodes, JOM 45 (1993) 41–43. H.B. Beer, The invention and industrial development of metal anodes, J. Electrochem. Soc. 127 (1980) 303C-307C. C. Comninellis, G.P. Vercesi, Characterization of DSA®-type oxygen evolving electrodes: Choice of a coating, J. Appl. Electrochem. 21 (1991) 335–345. S. Fierro, A. Kapa³ka, C. Comninellis, Electrochemical comparison between IrO2 prepared by thermal treatment of iridium metal and IrO2 prepared by thermal decomposition of H2IrCl6 solution, Electrochem. Commun. 12 (2010) 172–174. M.P. Groover, Fundamentos de manufactura moderna: materiales, procesos y sistemas. Prentice-Hall Hispanoamericana SA, Mexico, 1997. M. Pérez-Corona, A. Corona, E.D. Beltrán, J. Cárdenas, E. Bustos, Evaluation of IrO2-Ta2O5|Ti electrodes employed during the electroremediation of hydrocarbon-contaminated soil. Sustain. Environ. Res. 23 (2013) 279–284. J.-Y. Lee, An investigation on the electrochemical characteristics of Ta2O5- IrO2 anodes for the application of electrolysis process. Mater. Sci. Appl. 02 (2011) 237–243. A.M.Z. Ramalho, C.A. Martínez-Huitle, D.R. da Silva, Application of electrochemical technology for removing petroleum hydrocarbons from produced water using a DSA type anode at different flow rates, Fuel 89 (2010) 531–534. A. Yaqub, M.H. Isa, H. Ajab, Electrochemical degradation of polycyclic aromatic hydrocarbons in synthetic solution and produced water using a Ti/SnO2-Sb2O5-RuO2 anode. J. Environ. Eng. 141 (1) (2015) 1-8. Figure 1

Design, fabrication and high efficient visible-light assisted photoelectric-synergistic performance of 3-D mesoporous DSA electrodes

Novel photoelectrode was fabricated by using 3-D mesoporous Ti/Meso-TiO2/SnO2–Sb/SnO2–Sb–Ce dimensionally stable anode (DSA) as the basic film. Three kinds of Deguass-P25, TiO2–SnO2 and TiO2–SnO2–Sb–Ce photocatalysis were separately loaded on the basic electrode for the comparison and design of photoelectric-synergistic DSA electrode with high efficiency. Their morphologies and phase compositions were characterized by the scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Study shows that the five coating layers of TiO2–SnO2–Sb–Ce exhibits the best photoelectric activity to degrade the methylene blue solution. The current density of the photoelectric catalysis is 65% higher than the sum of the photocatalysis and electrocatalysis. The photoelectric decolorization ratio is 9.31 and 1.83 times more than that of photocatalysis and electrocatalysis, respectively. The visible-light assisted photoelectric-synergistic performance occurs when the light intensity is above 30mW·cm−2. The photoelectric decolorization ratio under 100mW·cm−2 achieves 97.8%, which is 1.38 times more than that of 30mW·cm−2. The supporting electrolyte of sodium sulfate and initial concentration of methylene blue are also investigated in this paper. The visible-light assisted photoelectric catalysis process can effectively degrade the organic pollutant under low voltage and has great significance in reducing energy consumption.

The electrolytic treatment of synthetic urine using DSA electrodes

In this work, the electrochemical treatment of synthetic urine by anodic oxidation using dimensionally stable anode (DSA) was studied. The influence of current density and temperature on the kinetics and efficiency of anodic oxidation was examined. The intermediates and the evolution of products were also monitored by HPLC and IC. Anodic oxidation achieves the almost total removal of COD, which is mainly transformed into carbon dioxide and oxalic acid. This latter compound explains the occurrence of residual TOC at large current densities. The electrochemical technology also attains a very significant removal of nitrogen, which is transformed into gaseous nitrogen through the formation of chloramines. The increase of current density leads to a decrease in the efficiency of the electrochemical process. Furthermore, the increase of the temperature has no significant influence on the oxidation rate but it contributes to a higher mineralization. The most efficient conditions were found to be low current densities (20Ahdm−3) and low temperatures (25°C), which in addition prevents the formation of chlorate and perchlorate ions in the reaction system.

Preparation and characterization of Sb2O5-doped Ti/RuO2-ZrO2 for dye decolorization by means of active chlorine

Textile industry is one of the major generators of wastewaters containing recalcitrant compounds such as dyes that jeopardize public health and environment. Electro-oxidation is an alternative method for treating recalcitrant compounds, and the key element for efficient degradation is the adequate use of dimensionally stable anode (DSA) electrodes to efficiently generate active chlorine, which degrades dyes contained in effluents into more environment-friendly compounds. This work is thereby aimed at preparing a novel DSA electrode for efficient generation of active chlorine. Two different dimensionally stable anodes (Ti/RuO2 and Sb2O5-doped Ti/RuO2-ZrO2) were prepared and then characterized by grazing incidence X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy, which corroborated the presence of RuO2, ZrO2, and Sb2O5. The comparison of electroactive areas, assessed by chronoamperometry, showed that Zr helps increase the area of the ternary electrode facilitating the formation of active chlorine. Active chlorine formation was further studied by cyclic voltammetry that revealed a reduction peak attributed to chlorine (product of chloride oxidation). Additionally, decolorization of model solutions that simulate textile effluents containing indigo carmine and reactive black 5 in media with and without chlorides was performed. In the chloride-containing medium, decolorization occurred at a faster rate than in the presence of sulfates. Decolorization of carmine indigo and reactive black 5 in the chloride-containing medium took 40 min and 2 h, respectively. In conclusion, the DSA electrode made of Sb2O5-doped Ti/RuO2-ZrO2 can efficiently generate the active chlorine for degradation of recalcitrant compounds.

Electrochemical oxidation of bio-refractory dye in a simulated textile industry effluent using DSA electrodes in a filter-press type FM01-LC reactor

This work presents a study on degradation of indigo carmine dye in a filter-press type FM01-LC reactor using Sb2O5-doped Ti/IrO2-SnO2 dimensionally stable anode (DSA) electrodes. Micro- and macroelectrolysis studies were carried out using solutions of 0.8 mM indigo carmine in 0.05 M NaCl, which resemble blue denim laundry industrial wastewater. Microelectrolysis results show the behaviour of DSA electrodes in comparison with the behaviour of boron-doped diamond (BDD) electrodes. In general, dye degradation reactions are carried out indirectly through active chlorine generated on DSA, whereas in the case of BDD electrodes more oxidizing species are formed, mainly OH radicals, on the electrode surface. The well-characterized geometry, flow pattern and mass transport of the FM01-LC reactor used in macroelectrolysis experiments allowed the evaluation of the effect of hydrodynamic conditions on the chlorine-mediated degradation rate. Four values of Reynolds number (Re) (93, 371, 464 and 557) at four current densities (50, 100, 150 and 200 A/m2) were tested. The results show that the degradation rate is independent of Re at low current density (50 A/m2) but becomes dependent on the Re at high current density (200 A/m2). This behaviour shows the central role of mass transport and the reactor parameters and design. The low energy consumption (2.02 and 9.04 kWh/m3 for complete discolouration and chemical oxygen demand elimination at 50 A/m2, respectively) and the low cost of DSA electrodes compared to BDD make DSA electrodes promising for practical application in treating industrial textile effluents. In the present study, chlorinated organic compounds were not detected.