Electro-Fenton degradation of the antibiotic sulfanilamide with Pt/carbon-felt and BDD/carbon-felt cells. Kinetics, reaction intermediates, and toxicity assessment

Fluoxetine removal by anodic oxidation using different anode materials and graphite cathode

Fluoxetine (FLX) is a selective serotonin reuptake inhibitor (SSRI) medication commonly used to treat mental health disorders, but it can be harmful to the environment if not properly disposed of due to incomplete metabolism. In this study, electrochemical anodic oxidation with mixed metal oxide anodes was studied as a method to remove FLX from water and wastewater. Iridium dioxide-coated titanium (Ti/IrO2) and ruthenium dioxide-coated Ti (Ti/RuO2) electrodes were found to be more effective than platinum-coated Ti (Ti/Pt) electrodes, with removal efficiencies of 91.5% and 93.9%, respectively. Optimal conditions for FLX removal were determined to be an applied current of 150 mA, initial pH of 5, and oxidation time of 120 min. The rate of FLX degradation (kFLX) for the Ti/Pt, Ti/IrO2, and Ti/RuO2 electrodes were determined to be 0.0081 min-1 (R2:0,8161), 0.0163 min-1 (R2:0,9823), and 0.0168 (R2:0,9901) min-1 for 25 mg/L initial FLX concentration, respectively. The kFLX values varied based on the initial FLX concentration and decreased as the initial FLX concentration increased. The specific energy consumption (SEC) after 120 min of operation was 51.0 kWh/m3 for the Ti/Pt electrode, 39.6 kWh/m3 for the Ti/IrO2 electrode, and 48.6 kWh/m3 for the Ti/RuO2 electrode under optimised conditions. Overall, electrochemical anodic oxidation is an effective method for removing FLX from water and wastewater, with Ti/IrO2 and Ti/RuO2 electrodes providing superior performance compared to Ti/Pt electrodes.

Mechanistic insights into sulfadimethoxine degradation via microbially driven Fenton reactions

Biodegradation, while cost-effective, is hindered by the requirement for specialized microorganisms and co-contaminants. Innovative biological technologies like the microbially driven Fenton reaction, hold promise for enhancing degradation efficiency. However, the intricate biochemical processes and essential steps for effective degradation in such systems have remained unclear. In this study, we harnessed the potential of the microbially driven Fenton reaction by employing Shewanella oneidensis MR-1 (MR-1). Our approach showcased remarkable efficacy in degrading a range of contaminants, including sulfadimethoxine (SDM), 4,4'-dibromodiphenyl ether (BDE-15) and atrazine (ATZ). Using SDM as a model contaminant of emergent contaminants (ECs), we unveiled that biodegradation relied on the generation of hydroxyl radicals (•OH) and involvement of oxidoreductases. Transcriptomic analysis shed light on the pivotal components of extracellular electron transfer (EET) during both anaerobic and aerobic periods. The presence of reactive oxidizing species induced cellular damage and impeded DNA repair, thereby affecting the Mtr pathway of EET. Moreover, the formation of vivianite hindered SDM degradation, underscoring the necessity of maintaining iron ions in the solution to ensure sustainable and efficient degradation. Overall, this study offers valuable insights into microbial technique for ECs degradation, providing a comprehensive understanding of degradation mechanisms during aerobic/anaerobic cycling.

Hydroquinone Ecotoxicity: Unveiling Risks in Soil and River Ecosystems with Insights into Microbial Resilience

Despite widespread industrial use, the environmental safety of hydroquinone (HQ), a benzene compound from plants used in processes like cosmetics, remains uncertain. This study evaluated the ecotoxicological impact of HQ on soil and river environments, utilizing non-target indicator organisms from diverse trophic levels: Daphnia magna, Aliivibrio fischeri, Allium cepa, and Eisenia fetida. For a more environmentally realistic assessment, microbial communities from a river and untreated soil underwent 16S rRNA gene sequencing, with growth and changes in community-level physiological profiling assessed using Biolog EcoPlate™ assays. The water indicator D. magna exhibited the highest sensitivity to HQ (EC50 = 0.142 µg/mL), followed by A. fischeri (EC50 = 1.446 µg/mL), and A. cepa (LC50 = 7.631 µg/mL), while E. fetida showed the highest resistance (EC50 = 234 mg/Kg). Remarkably, microbial communities mitigated HQ impact in both aquatic and terrestrial environments. River microorganisms displayed minimal inhibition, except for a significant reduction in polymer metabolism at the highest concentration (100 µg/mL). Soil communities demonstrated resilience up to 100 µg/mL, beyond which there was a significant decrease in population growth and the capacity to metabolize carbohydrates and polymers. Despite microbial mitigation, HQ remains highly toxic to various trophic levels, emphasizing the necessity for environmental regulations.

Electrochemical degradation of favipiravir (anti-viral) drug from aqueous solution: optimization of operating parameters using the response surface method

The aim of the current study is to investigate the efficacy of the electro-Fenton process in the degradation of favipiravir drugs from aqueous solutions, which has increased in use as a result of the COVID-19 pandemic. The Response Surface Methodology (RSM) was developed using a Central Composite Design (CCD) in which five independent variables, including Fe2+ concentration, current density, initial FVP concentration, pH, and reaction time, were coded with high and low levels, and the maximum removal percentage of FVP (97.8%) and COD (91.65%) were determined as responses. In the EF process, 530 mg/L H2O2 was produced in-situ by cathodic reduction of O2 in aqueous solution and thus FVP has been successfully oxidized through hydroxyl radicals. The H2O2/Fe2+ ratio was determined to be 0.51 under optimum conditions. At the end of the experiment, the maximum energy consumption was found to be 2.12 kWh per g COD. The FVP was completely mineralized in a very short time by the EF process, according to the LC-MS/MS examination. The EF process followed the pseudo first-order kinetic model with the rate constants of 0.023, 0.016 and 0.006 1/min for pH 2, 3 and 4, respectively. According to the findings of this study, the electro-Fenton process is an effective method for removing FVP from aqueous solutions. To the authors' knowledge, this is the first study to show the degradation and optimum conditions of FVP in aqueous solution using the electro-Fenton (EF) process.

Electro-Fenton-Based Technologies for Selectively Degrading Antibiotics in Aqueous Media

The viability of the Electro-Fenton (EF) process in the selective degradation of penicillin G (PenG) in complex solutions has been studied. The role of the anode material (boron-doped diamond (BDD) or mixed metal oxide (MMO)) and the cathode 3D support (foam or mesh), as well as the synergistic effect of UVC light irradiation (photoelectron-Fenton, PEF), have been evaluated. The results show that Pen G can be efficiently and selectively removed by EF, obtaining higher PenG removal rates when using the BDD anode (100%) than when using the MMO anode (75.5%). Additionally, mineralization is not favored under the experimental conditions tested (pH 3, 5 mA cm−2), since both aromatic and carboxylic acids accumulate in the reaction system as final products. In this regard, the EF-treated solution presents a high biological oxygen demand and a low percentage of Vibrio fischeri inhibition, which leads to high biodegradability and low toxicity of this final effluent. Furthermore, the combination with UVC radiation in the PEF process shows a clear synergistic effect on the degradation of penicillin G: 166.67% and 83.18% using MMO and BBD anodes, respectively. The specific energy required to attain the complete removal of PenG and high inhibition of the antibiotic effect is less than 0.05 Ah dm−3. This confirms that PEF can be efficiently used as a pretreatment of conventional wastewater treatment plants to decrease the chemical risk of complex solutions polluted with antibiotics.

Kinetic and mechanistic investigation of geosmin and 2-methylisoborneol degradation using UV-assisted photoelectrochemical

The taste and odor (T&O) problem represented by 2-methylisoborneol (2-MIB) and geosmin (GSM) in water is the multiple undesirable substances in the drinking water and the aquatic industry. In this study, the UV-assisted photoelectrochemical, a prospective advanced oxidation process (AOP), was evaluated for the degradation of 2-MIB and GSM. In contrast to UV photochemical and electrochemical, the degradation ratio of GSM (2-MIB) increase to 96% (95%) in 25 min. The removal ratio and rate depended on reaction time, electrolyte concentration, current density, and water quality parameters (e.g. pH, HCO₃^-, natural organic matter, and tap water). Among these parameters, a high concentration of electrolyte and acidic solutions could accelerate the rate and increase the ratio, while alkaline conditions and the impurity content had negative effects. Furthermore, the significant role of various reactive species (e.g. HO∙, Cl, ClO, etc) were highlighted by scavenging experiments. Complex free radicals exist was further verified by electron paramagnetic resonance spectroscopy (EPR) experiments. The intermediates were identified and the possible degradation pathways during the UV-assisted photoelectrochemical reactions of both compounds were proposed. Overall, the UV-assisted photoelectrochemical is beneficial to the removal of GSM and 2-MIB in water.

In-situ generation of reactive oxygen species using combination of electrochemical oxidation and metal sulfide

In-situ chemical oxidation (ISCO) is commonly practiced to degrade organic pollutants in various fields. However, ISCO is deteriorated the oxidation efficiency due to the non-selective and self-decomposition of reagents. Therefore, in-situ generation of oxidants is being proposed to compensate for the demerits of conventional ISCO. In this study, the aim is to suggest a novel in-situ generation system using the combination of electrochemical oxidation (EO) and pyrite oxidation. It is hypothesized that EO system can generate the oxygen species, which can activate the pyrite surface to produce more oxidants. We evaluated three systems (1) EO system (2) pyrite oxidation system (3) combined system using sulfanilamide as a common antibiotic. The EO system degraded completely sulfanilamide and generated 150 μM of H₂O₂ and 8 mg/L of DO even at 10 mA. In other words, EO system can directly oxidize the sulfanilamide and produce oxygen species. The pyrite system produced 204 and 24 μM of hydroxyl radicals at pH 3 under oxic and anoxic conditions, respectively, and 118 and 20 μM at pH 7. Pyrite oxidation can generate more reactive species in the presence of oxygen. The combined system enhanced the oxidation-rate constant to 1.5 times (from 0.2561 to 0.3502 h^-1). The additional supply of oxygen showed a higher oxidation rate to 1.5 and 1.3 times higher than single EO or pyrite oxidation, respectively. As a result, the co-presence of pyrite and oxygen shows a synergistic effect on the oxidation of the organic pollutant. Our results suggest that electrochemical generation of the oxygen species in the presence of pyrite is a promising technique to oxidize organic pollutants in groundwater.

Determination of short-chain carboxylic acids and non-targeted analysis of water samples treated by wet air oxidation using gas chromatography-mass spectrometry

A method based on gas chromatography coupled with electron ionization mass spectrometry employing N,O-bis(trimethylsilyl)trifluoroacetamide with trimethylchlorosilane as derivatization agent was developed to quantify short-chain carboxylic acids (C₁-C₆) in hospital wastewater treated by wet air oxidation, an advanced oxidation process. Extraction from water and derivatization of volatile and semi-volatile short chain carboxylic acids were optimized and validated and limits of quantification (LOQ = 0.049 mg L^-1-4.15 mg L^-1), repeatability (RSD = 1.7-12.8%), recovery (31-119%) and trueness (relative bias = -19.0-3.4%) were acceptable. The validated method was successfully applied to monitor the concentration of organic acids formed after wet air oxidation of water samples. Results showed that the method described herein allowed to identify 38% and up to 46% of the final chemical oxygen demand's composition after wet air oxidation of acetaminophen spiked in deionised water and hospital wastewater samples, respectively. The developed method also allowed to perform qualitative non-targeted analysis in hospital wastewater samples after treatment. Results demonstrated that glycerol, methenamine, and benzoic acid were also present in the samples and their presence was confirmed with reference standards.

Carbon-Based Nanocomposites as Fenton-Like Catalysts in Wastewater Treatment Applications: A Review

Advanced oxidation (e.g., fenton-like reagent oxidation and ozone oxidation) is a highly important technology that uses strong oxidizing free radicals to degrade organic pollutants and mineralize them. The fenton-like reactions have the characteristics of low cost, simple operation, thorough reaction and no secondary pollution. Fenton-like reagents refer to a strong oxidation system composed of transition metal ions (e.g., Fe3+, Mn2+ and Ag+) and oxidants (hydrogen peroxide, potassium persulfate, sodium persulfate, etc). Graphene and carbon nanotube possess a distinctive mechanical strength, flexibility, electrical and thermal conductivity and a very large specific surface area, which can work as an excellent carrier to disperse the catalyst and prevent its agglomeration. Fullerene can synergize with iron-based materials to promote the reaction of hydroxyl groups with organic pollutants and enhance the catalytic effect. Fenton-like catalysts influence the catalytic behavior by inducing electron transfer under strong interactions with the support. Due to the short lifespan of free radicals, the treatment effect is usually enhanced with the assistance of external conditions (ultraviolet and electric fields) to expand the application of fenton-like catalysts in water treatment. There are mainly light-fenton, electro-fenton and photoelectric-fenton methods. Fenton-like catalysts can be prepared by hydrothermal method, impregnation and coordination-precipitation approaches. The structures and properties of the catalysts are characterized by a variety of techniques, such as high-resolution transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption near-edge structure spectroscopy. In this paper, we review the mechanisms, preparation methods, characterizations and applications status of fenton-like reagents in industrial wastewater treatment, and summarize the recycling of these catalysts and describe prospects for their future research directions.

Photoelectro-Fenton treatment of pesticide triclopyr at neutral pH using Fe(III)-EDDS under UVA light or sunlight

One of the main challenges of electrochemical Fenton-based processes is the treatment of organic pollutants at near-neutral pH. As a potential approach to this problem, this work addresses the use of a low content of soluble chelated metal catalyst, formed between Fe(III) and ethylenediamine-N,N'-disuccinic (EDDS) acid (1:1), to degrade the herbicide triclopyr in 0.050 M Na₂SO₄ solutions at pH 7.0 by photoelectro-Fenton with UVA light or sunlight (PEF and SPEF, respectively). Comparison with electro-Fenton treatments revealed the crucial role of the photo-Fenton-like reaction, since this promoted the production of soluble Fe(II) that enhanced the pesticide removal. Hydroxyl radicals formed at the anode surface and in the bulk were the main oxidants. A boron-doped diamond (BDD) anode yielded a greater mineralization than an IrO₂-based one, at the expense of reduced cost-effectiveness. The effect of catalyst concentration and current density on the performance of PEF with BDD was examined. The PEF trials in 0.25 mM Na₂SO₄ + 0.35 mM NaCl medium showed a large influence of generated active chlorine as oxidant, being IrO₂ more suitable than RuO₂ and BDD. In SPEF with BDD, the higher light intensity from solar photons accelerated the removal of the catalyst and triclopyr, with small effect on mineralization. A plausible route for the herbicide degradation by Fe(III)-EDDS-catalyzed PEF and SPEF is finally proposed based on detected byproducts: three heteroaromatic and four linear N-aliphatic compounds, formamide, and tartronic and oxamic acids.

Efficient mineralization of sulfanilamide over oxygen vacancy-rich NiFe-LDH nanosheets array during electro-fenton process

Electrochemical degradation of toxic sulfanilamide with inexpensive approach is in urgent demand due to the harmful effects of sulfanilamide for both humans and aquatic environments. Here, we reported an efficient mineralization of sulfanilamide by using NiFe-layered double hydroxide (NiFe-LDH) nanosheets array with abundant oxygen vacancies that was in situ grown on exfoliated graphene (EG) by a simple hydrothermal treatment at different temperatures. The hydrothermal temperature was carefully analyzed for control synthesis of oxygen vacancy-rich NiFe-LDH/EG nanosheets array (NiFe-LDH/EG-OVr) for sulfanilamide degradation. Owing to the abundant oxygen vacancies, NiFe-LDH/EG-OVr rapidly generated hydrogen peroxide (H₂O₂) and hydroxyl radical (•OH) during electro-Fenton (EF) process_, which resulted in the 98% mineralization of sulfanilamide in first 80 min. The radicals trapping experiments revealed that the •OH radicals was participated as the main active oxidation species in the efficient mineralization of sulfanilamide. The present results indicated that the oxidative attack by •OH radicals initiated the degradation process of sulfanilamide. During the total degradation of sulfanilamide, several organic compounds including aminophenol, hydroquinone, and oxalic acid, were identified as main intermediates by using gas chromatography-mass spectroscopy (GC-MS) and high-performance liquid chromatography-mass spectroscopy (HPLC-MS).

Fabrication of sand-based novel adsorbents embedded with biochar or binding agents via calcite precipitation for sulfathiazole scavenging

Fabrication of efficient and low-cost adsorbents through enzyme induced carbonate precipitation (EICP) of sand embedded with binding agents for sulfathiazole (STZ) removal is reported for the first time. Sand enriched with biochar (300 °C, 500 °C, and 700 °C), xanthan gum, guar gum, bentonite, or sodium alginate (1% w/w ratios) was cemented via EICP technique. Enrichment with binding agents decreased the unconfined compressive strength, improved the porosity, and induced functional groups. Biochar enrichment reduced the pH, and increased the calcite contents and electrical conductivity. Fixed-bed column adsorption trials revealed that biochars enrichment resulted in the highest STZ removal (64.7-87.9%) from water at initial STZ concentration of 50 mg L^-1, than the adsorbents enriched with other binding agents. Yoon-Nelson and Thomas kinetic models were fitted well to the adsorption data (R² = 0.91-0.98). The adsorbents embedded with 700 °C biochar (BC7) exhibited the highest Yoon-Nelson rate constants (0.087 L min^-1), 50% breakthrough time (58.056 min), and Thomas model-predicted maximum adsorption capacity (4.925 mg g^-1). Overall, BC7 removed 168% higher STZ from water than pristine cemented sand. Post-adsorption XRD and FTIR analyses suggested the binding of STZ onto the adsorbents. π-π electron-donor-acceptor interactions, aided-by electrostatic interactions and H-bonding were the main STZ adsorption mechanisms.

Biodegradation mechanisms of sulfonamides by Phanerochaete chrysosporium - Luffa fiber system revealed at the transcriptome level

The overuse of antibiotics and subsequent enrichment of antibiotic resistant microbes in the natural and built environments is a severe threat to global public health. In this study, a Phanerochaete chrysosporium fungal-luffa fiber system was found to efficiently biodegrade two sulfonamides, sulfadimethoxine (SDM) and sulfadizine (SDZ), in cow urine wastewater. Biodegradation pathways were proposed on the basis of key metabolites identified using high performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry (HPLC-QqTOF-MS). Transcriptomic, metabolomic, and free radical analyses were performed to explore the functional groups and detailed molecular mechanisms of SDM and SDZ degradation. A total of 27 UniGene clusters showed significant differences between luffa fiber and luffa fiber-free systems, which were significantly correlated to cellulose catabolism, carbohydrate metabolism, and oxidoreductase activity. Carbohydrate-active enzymes and oxidoreductases appear to play particularly important roles in SDM and SDZ degradation. Electron paramagnetic resonance (EPR) spectroscopy revealed the generation and evolution of OH and R during the biodegradation of SDM and SDZ, suggesting that beyond enzymatic degradation, SDM and SDZ were also transformed through a free radical pathway. Luffa fiber also acts as a co-substrate to improve the activity of enzymes for the degradation of SDM and SDZ. This research provides a potential strategy for removing SDM and SDZ from agricultural and industrial wastewater using fungal-luffa fiber systems.

Enhanced electro-Fenton degradation of sulfonamides using the N, S co-doped cathode: Mechanism for H2O2 formation and pollutants decay

Facing low reactivity/selectivity of oxygen reduction reaction (ORR) in electro-Fenton (EF), N, S atoms were introduced into carbon-based cathode. "End-on" O₂ adsorption was achieved by adjusting electronic nature via N doping, while *OOH binding capability was tuned by spin density variation via S doping. Results showed the optimized N, S co-doped cathode presented a 42.47% improvement of H₂O₂ accumulation (7.95 ± 0.02 mg L^-1 cm^-2). According to density functional theory (DFT), N, S co-doped structure favored the "end-on" O₂ adsorption as adsorption energy dropped to - 2.24 eV. Moreover, O-O/C-O bond lengths variation proved a possibility for *OOH desorption. The elaborated cathode was used in EF for sulfonamides (SAs) decay. A 100% removal rate of sulfadiazine (SDZ), sulfathiazole (STZ) and sulfadimethoxine (SDM) was achieved within 60 min, among which SDZ tended to be degraded easily. Because the absolute hardness (η) of those pollutants is ranked as follows: η_SDM> η_STZ> η_SDZ. Degradation pathways were proposed based on the detected byproducts, along with toxicity was evaluated by ecological structure-activity relationship (ECOSAR) program. Results showed that toxic intermediates generated were reduced or even disappeared. EF with N, S co-doped cathode provides a promising process for antibiotics wastewater treatment.

Removal of bisphenol A from acidic sulfate medium and urban wastewater using persulfate activated with electroregenerated Fe2

Model solutions of bisphenol A (BPA) in 0.050 M Na₂SO₄ at pH 3.0 have been treated by the electro/Fe²⁺/persulfate process. The activation of 5.0 mM persulfate with 0.20 mM Fe²⁺ yielded a mixture of sulfate radical anion (SO₄^-) and OH, although quenching tests revealed the prevalence of the former species as the main oxidizing agent. In trials run in an IrO₂/carbon-felt cell, 98.4% degradation was achieved alongside 61.8% mineralization. The energy consumption was 253.9 kWh (kg TOC)^-1, becoming more cost-effective as compared to cells with boron-doped diamond and Pt anodes. Carbon felt outperformed stainless steel as cathode because of the faster Fe²⁺ regeneration. All BPA concentration decays agreed with a pseudo-fist-order kinetics. The effect of persulfate, Fe²⁺ and BPA concentrations as well as of the applied current on the degradation process was assessed. Two dehydroxylated and three hydroxylated monobenzenic by-products appeared upon SO₄^- and OH attack, respectively. The analogous treatment of BPA spiked into urban wastewater yielded a faster degradation and mineralization due to the co-generation of HClO and the larger OH production as SO₄^- reacted with Cl^-.

Simultaneous persulfate activation by electrogenerated H2O2 and anodic oxidation at a boron-doped diamond anode for the treatment of dye solutions

The development of new or upgraded electrochemical water treatment technologies is considered a topic of great interest. Here, Tartrazine azo dye solutions were treated by means of a quite innovative dual electrochemical persulfate (S₂O₈^2-, PS) activation that combines H₂O₂ generation at an air-diffusion cathode and anodic oxidation (AO) at a boron-doped diamond (BDD) anode using a stirred tank reactor. This so-called AO-H₂O₂/PS process was compared to AO with stainless steel cathode, both in 50 mM Na₂SO₄ medium, finding the oxidation power increasing as: AO < AO-H₂O₂ < AO/PS < AO-H₂O₂/PS. In the latter, the dye and its products were mainly destroyed by: (i) hydroxyl radicals, formed either from water oxidation at BDD surface or via reaction between H₂O₂ and S₂O₈^2-, and (ii) sulfate radical anion, formed from the latter reaction, thermal PS activation and cathodic S₂O₈^2- reduction. Hydroxyl radicals prevailed as oxidizing agents, as deduced from trials with tert-butanol and methanol. The reaction between S₂O₈^2- and accumulated H₂O₂ was favored as temperature increased from 25 to 45 °C. The effect of PS content up to 36 mM, dye concentration within the range 0.22-0.88 mM, current density (j) between 8.3 and 33.3 mA cm^-2 and pH between 3.0 and 9.0 on the process performance was examined. All decolorization profiles agreed with a pseudo-first-order kinetics. The best results for treating 0.44 mM dye were attained with 36 mM PS at pH 3.0, j = 16.7 mA cm^-2 and 45 °C, yielding total loss of color, 62% TOC removal and 50% mineralization current efficiency after 360 min. The slow mineralization was attributed to the persistence of recalcitrant byproducts like maleic, acetic, oxalic, formic and oxamic acids. It is concluded that the novel AO-H₂O₂/PS process is more effective than AO/PS to treat Tartrazine solutions, being advisable to extend the study to other organic pollutants.

Improving Fe-based heterogeneous Electro-Fenton nano catalyst using transition metals in a novel orbiting electrodes reactor

In recent decades the electro-Fenton process has widely been utilized for removing recalcitrant compounds. However, this process is accompanied by several problems such as limited working pH range, production of significant amount of iron sludge, and incapability in reusing used iron ions. Hence, the heterogeneous electro-Fenton process is a convenient way to address these problems. One of the shortcomings of this method, in comparison with the homogeneous electro-Fenton process, is its lower reaction rate. In the first phase of this study, a heterogeneous Fe-based nanocatalyst was prepared. After optimizing the affecting parameters, three transition metals (M: Cu, Co and, Cr) were used in the second phase of the study to improve the performance of this nanocatalyst in removing the indicator pollutant (acid blue 25). The characteristics of nanocatalysts were determined via FESEM, XRD, FTIR, and N₂ adsorption-desorption techniques. The results indicated an enhancement in dye removal efficiency (nearly 8 percent), and the reaction rate (nearly 64 percent) due to the nanocatalysts improved by the presence of transition metals. The reactions with Fe-based nanocatalyst containing copper ions in pH = 3, initial dye concentration = 200 mg L^-1, I = 3.57 mA cm^-2, nanocatalyst concentration = 100 mg L^-1, electrodes angular velocity = 50 rpm, Na₂SO₄ concentration = 0.01 M were capable of removing 97% of dye, 79% of COD and, 65% of TOC. The nanocatalysts were used in 5 cycles, and the dye removal efficiency did not drop considerably, a feature that adds to their importance from an economic point of view. The concentration of leached transition metals into the solution was measured using the ICP-AES technique, which was less than the allowable Iranian standard concentration of discharge into the surface water bodies, thus no need for secondary treatment of wastewater.

Expanding the application of photoelectro-Fenton treatment to urban wastewater using the Fe(III)-EDDS complex

This work reports the first investigation on the use of EDDS as chelating agent in photoelectro-Fenton (PEF) treatment of water at near-neutral pH. As a case study, the removal of the antidepressant fluoxetine was optimized, using an electrochemical cell composed of an IrO₂-based anode an air-diffusion cathode for in-situ H₂O₂ production. Electrolytic trials at constant current were made in ultrapure water with different electrolytes, as well as in urban wastewater (secondary effluent) at pH 7.2. PEF with Fe(III)-EDDS (1:1) complex as catalyst outperformed electro-Fenton and PEF processes with uncomplexed Fe(II) or Fe(III). This can be explained by: (i) the larger solubilization of iron ions during the trials, favoring the production of ^•OH from Fenton-like reactions between H₂O₂ and Fe(II)-EDDS or Fe(III)-EDDS, and (ii) the occurrence of Fe(II) regeneration from Fe(III)-EDDS photoreduction, which was more efficient than conventional photo-Fenton reaction with uncomplexed Fe(III). The greatest drug concentration decays were achieved at low pH, using only 0.10 mM Fe(III)-EDDS, although complete removal in wastewater was feasible only with 0.20 mM Fe(III)-EDDS due to the greater formation of ^•OH. The effect of the applied current and anode nature was rather insignificant. A progressive destruction of the catalytic complex was unveiled, whereupon the mineralization mainly progressed thanks to the action of ^•OH adsorbed on the anode surface. Despite the incomplete mineralization using BDD as the anode, a remarkable toxicity decrease was determined. Fluoxetine degradation yielded F^- and NO₃^- ions, along with several aromatic intermediates. These included two chloro-organics, as a result of the anodic oxidation of Cl^- to active chlorine. A detailed mechanism for the Fe(III)-EDDS-catalyzed PEF treatment of fluoxetine in urban wastewater is finally proposed.

Influence of electrolysis conditions on the treatment of herbicide bentazon using artificial UVA radiation and sunlight. Identification of oxidation products

The main objective of this work is to demonstrate the viability of solar photoelectro-Fenton (SPEF) process to degrade pesticides in urban wastewater matrix, selecting the herbicide bentazon as a model molecule. In order to provide a correct assessment of the role of the different oxidants and catalysts involved, bentazon was comparatively treated by anodic oxidation with electrogenerated H₂O₂ (AO-H₂O₂), electro-Fenton (EF) and UVA-assisted EF (i.e., PEF) processes as well, either in sulfate or chloride media. Trials were made in a stirred tank reactor with an air-diffusion cathode and a boron-doped diamond (BDD), RuO₂-based or Pt anode. In chlorinated matrices, the herbicide disappeared more rapidly using a RuO₂-based anode because of the generated active chlorine. The best mineralization performance was always obtained using BDD due to its higher oxidation power, which allowed the complete destruction of refractory chloroderivatives. A concentration of 0.50 mM Fe²⁺ was found optimal to catalyze Fenton's reaction, largely enhancing the mineralization process under the action of OH. Among photo-assisted treatments, sunlight was proven superior to a UVA lamp to promote the photolysis of intermediates, owing to its greater UV irradiance and contribution of visible photons, although PEF also allowed achieving a large mineralization. In all cases, bentazon decay obeyed a pseudo-first-order kinetics. SPEF treatment in urban wastewater using BDD at only 16.6 mA cm^-2 yielded 63.2% mineralization. A thorough, original reaction pathway for bentazon degradation is proposed, including seven non-chlorinated aromatics, sixteen chloroaromatics and two chloroaliphatics identified by GC-MS, most of them not previously reported in literature. Ion-exclusion HPLC allowed the detection of seven short-chain linear carboxylic acids.

A comprehensive performance evaluation of heterogeneous Bi2Fe4O9/peroxymonosulfate system for sulfamethoxazole degradation

In this study, a Bi₂Fe₄O₉ catalyst with nanoplate morphology was fabricated using a facile hydrothermal method. It was used as a catalyst to activate peroxymonosulfate (PMS) for aqueous sulfamethoxazole (SMX) removal. A comprehensive performance evaluation of the Bi₂Fe₄O₉/PMS system was conducted by investigating the effects of pH, PMS dosage, catalyst loading, SMX concentration, temperature, and halides (Cl^- and Br^-) on the degradation of SMX. The Bi₂Fe₄O₉/PMS system demonstrated a remarkable catalytic activity with >95% SMX removal within 30 min (conditions: pH 3.8, [Bi₂Fe₄O₉] = 0.1 g L^-1, [SMX]:[PMS] mol ratio =1:20). It was found that both Cl^- and Br^- can lead to the formation of PMS-induced reactive halide species (i.e. HClO, HBrO, and Br₂) which can also react with SMX forming halogenated SMX byproducts. Based on the detected degradation byproducts, the major SMX degradation pathway in the Bi₂Fe₄O₉/PMS system is proposed. The SMX degradation by Bi₂Fe₄O₉/PMS system in the wastewater secondary effluent (SE) was also investigated. The results showed that SMX degradation rate in the SE was relatively slower than in the deionized water due to (i) reactive radical scavenging by water matrix species found in SE (e.g.: dissolved organic matters (DOCs), etc.), and (ii) partial deactivation of the catalyst by DOCs. Nevertheless, the selectivity of the SO₄^•- towards SMX degradation was evidenced from the rapid SMX degradation despite the high background DOCs in the SE. At least four times the dosage of PMS is required for SMX degradation in the SE to achieve a similar SMX removal efficiency to that of the deionized water matrix.

Fenton-based electrochemical degradation of metolachlor in aqueous solution by means of BDD and Pt electrodes: influencing factors and reaction pathways

This work explores the role of electrode material and the oxidation ability of electrochemical advanced oxidation processes (EAOPs), such as electro-oxidation (EO) with or without H₂O₂ production, electro-Fenton (EF), and UVA photoelectron-Fenton (PEF), in the degradation of metolachlor. The performance of the EAOPs using Boron-doped diamond (BDD) or Pt as anode has been compared from the analysis of decay kinetics, mineralization profile, and energy consumption using small undivided batch cell. Metolachlor concentration always decays following a pseudo-first-order kinetics. Using the Pt anode, none of the processes reaches 30% mineralization, including PEF. In contrast, the BDD anode showed a higher mineralization rate allowing almost total mineralization in PEF due to the synergetic action of UVA light and oxidant hydroxyl radicals formed in the bulk from Fenton's reaction, as well as in the BDD, which has large reactivity to oxidize the pollutants. The increase in current density and decrease in metolachlor concentration accelerated the mineralization in PEF, although lower current efficiency and higher energy consumption was obtained. The GC-MS and HPLC analysis allowed the identification of up to 17 aromatics intermediates and 7 short-chain carboxylic acids. Finally, a reaction pathway for metolachlor mineralization by EAOPs is proposed. PEF with BDD allowed total removal of the herbicide in real water matrix and a high mineralization (83.82%).

Total mineralization of mixtures of Tartrazine, Ponceau SS and Direct Blue 71 azo dyes by solar photoelectro-Fenton in pre-pilot plant

Mixtures of monoazo Tartrazine, diazo Ponceau SS and triazo Direct Blue 71 dyes with 105 mg L^-1 of total organic carbon (TOC) in 0.050 M Na₂SO₄ at pH 3.0 have been treated by solar photoelectro-Fenton (SPEF). Experiments were carried out in a 2.5 L pre-pilot plant with a Pt/air-diffusion cell coupled to a solar planar photoreactor. Comparative trials were made by anodic oxidation with electrogenerated H₂O₂ (AO-H₂O₂) and electro-Fenton (EF) to better understand the role of oxidizing agents. AO-H₂O₂ gave poor degradation due to the low oxidation ability of OH formed at the Pt anode and H₂O₂ produced at the cathode. Similar color removal was achieved in EF and SPEF because the main oxidant was OH formed in the bulk from Fenton's reaction. EF yielded partial mineralization by formation of molecules with high stability against OH. In contrast, these by-products were rapidly photolyzed under sunlight irradiation in SPEF, which was the most powerful treatment. Up to 8 linear final carboxylic acids were detected, along with the release of sulfate and ammonium ions. The effect of Fe²⁺ and azo dye concentrations, and current density over the SPEF performance was assessed. Total mineralization of azo dyes mixtures occurred when operating up to 105 mg L^-1 TOC with 0.50 mM Fe²⁺ at 100 mA cm^-2.

On the performance of electrocatalytic anodes for photoelectro-Fenton treatment of synthetic solutions and real water spiked with the herbicide chloramben

The destruction of the herbicide chloramben in 0.050 M Na₂SO₄ solutions at natural pH has been studied by photoelectro-Fenton with UVA light (PEF). The trials were carried out in a cell equipped with an air-diffusion cathode for H₂O₂ generation and different electrocatalytic anodes, namely active IrO₂-based and RuO₂-based electrodes and non-active boron-doped diamond (BDD) and PbO₂ ones. Similar removal rates were found regardless of the anode nature because the herbicide was mainly oxidized by OH formed from Fenton's reaction, which was enhanced by UVA-induced photo-Fenton reaction. The use of an IrO₂-based anode led to almost total mineralization at high current density, as also occurred with the powerful BDD anode, since photoactive intermediates originated from OH-mediated oxidation were degraded under irradiation with UVA light. The good performance of the IrO₂-based anode in PEF was confirmed at different current densities and herbicide concentrations. The presence of Cl^- in the medium caused a slight deceleration of herbicide removal as well as mineralization inhibition, owing to the production of active chlorine with consequent formation of persistent chloroderivatives. Seven aromatic products along with oxalic and oxamic acids were identified in sulfate medium. Five aromatic derivatives were detected in Cl^--containing matrix, corroborating the generation of organochlorine compounds. In secondary effluent, larger mineralization was achieved by PEF with a BDD anode due to its high oxidation ability to destroy the chloroderivatives, although an acceptable performance was also obtained using an IrO₂-based anode.

Bioelectro-Fenton: evaluation of a combined biological-advanced oxidation treatment for pharmaceutical wastewater

Electro-Fenton (EF), an advanced oxidation process, can be combined with a biological process for efficient treatment of wastewater containing refractory pollutants such as pharmaceuticals. In this study, a biological process was implemented in a sequencing batch reactor (SBR), which was either preceded or followed by EF treatment. The main goal was to evaluate the potential of two sequences of a combined electrochemical-biological process: EF/SBR and SBR/EF for the treatment of real wastewater spiked with 0.1 mM of caffeine and 5-fluorouracil. The biological removal of COD and pharmaceuticals was improved by extending the acclimation time and increasing concentration of biomass in the SBR. Hardly biodegradable caffeine and COD were completely removed during the EF post-treatment (SBR/EF). During the EF/SBR sequence, complete removal of pharmaceuticals was achieved by EF within 30 min at applied current 800 mA. With a current of 500 and 800 mA, the initially very low BOD₅/COD ratio increased up to 0.38 and 0.58, respectively, after 30 min. The efficiency of the biological post-treatment was influenced by the biodegradability enhancement after EF pre-treatment. The choice of an adequate sequence of such a combined process is significantly related to the wastewater characteristics as well as the treatment objectives.

Electro-Fenton oxidation of para-aminosalicylic acid: degradation kinetics and mineralization pathway using Pt/carbon-felt and BDD/carbon-felt cells

Degradation of a widely used antibiotic, the para-aminosalicylic acid (PAS), and mineralization of its aqueous solution was investigated by electro-Fenton process using Pt/carbon-felt and boron-doped diamond (BDD)/carbon-felt cells with applied currents in the range of 50-1000 mA. This process produces the highly oxidizing species, the hydroxyl radical (^•OH), which is mainly responsible for the oxidative degradation of PAS. An absolute rate constant of 4.17 × 10⁹ M^-1 s^-1 for the oxidation of PAS by ^●OH was determined from the competition kinetics method. Degradation rate of PAS increased with current reaching an optimal value of 500 mA with complete disappearance of 0.1 mM PAS at 7 min using Pt/carbon-felt cell. The optimum degradation rate was reached at 300 mA for BDD/carbon-felt. The latter cell was found more efficient in total organic carbon (TOC) removal where a complete mineralization was achieved within 240 min. A multi-step mineralization process was observed with the formation of a number of aromatic intermediates, short-chain carboxylic acids, and inorganic ions. Eight aromatic intermediate products were identified using both LC-Q-ToF-MS and GC-MS techniques. These products were the result of hydroxylation of PAS followed by multiple additions of hydroxyl radicals to form polyhydroxylated derivatives. HPLC and GC/MS analyses demonstrated that extended oxidation of these intermediate products conducted to the formation of various short-chain carboxylic acids. Prolonged electrolysis resulted in a complete mineralization of PAS with the evolution of inorganic ions such as NO₃^- and NH₄⁺. Based on the identified intermediates, carboxylic acids and inorganic ions, a plausible mineralization pathway is also deduced. The remarkably high degree of mineralization (100%) achieved by the present EF process highlights the potential application of this technique to the complete removal of salicylic acid-based pharmaceuticals from contaminated water.

Current advances and trends in electro-Fenton process using heterogeneous catalysts - A review

Over the last decades, advanced oxidation processes have often been used alone, or combined with other techniques, for remediation of ground and surface water pollutants. The application of heterogeneous catalysis to electrochemical advanced oxidation processes is especially useful due to its efficiency and environmental safety. Among those processes, electro-Fenton stands out as the one in which heterogeneous catalysis has been broadly applied. Thus, this review has introduced an up-to-date collation of the current knowledge of the heterogeneous electro-Fenton process, highlighting recent advances in the use of different catalysts such as iron minerals (pyrite, magnetite or goethite), prepared catalysts by the load of metals in inorganic and organic materials, nanoparticles, and the inclusion of catalysts on the cathode. The effects of physical-chemical parameters as well as the mechanisms involved are critically assessed. Finally, although the utilization of this process to remediation of wastewater overwhelmingly outnumber other utilities, several applications have been described in the context of regeneration of adsorbent or the remediation of soils as clear examples of the feasibility of the electro-Fenton process to solve different environmental problems.

Lindane degradation by electrooxidation process: Effect of electrode materials on oxidation and mineralization kinetics

This study focuses on the effect of electrode materials on abatement of lindane (an organochlorine pesticide) by electrooxidation process. Comparative performances of different anodic (platinum (Pt), dimensionally stable anode (DSA) and boron-doped diamond (BDD)) and cathodic (carbon sponge (CS), carbon felt (CF) and stainless steel (SS)) materials on lindane electrooxidation and mineralization were investigated. Special attention was paid to determine the role of chlorine active species during the electrooxidation process. The results showed that better performances were obtained when using a BDD anode and CF cathode cell. The influence of the current density was assessed to optimize the oxidation of lindane and the mineralization of its aqueous solution. A quick (10 min) and complete oxidation of 10 mg L^-1 lindane solution and relatively high mineralization degree (80% TOC removal) at 4 h electrolysis were achieved at 8.33 mA cm^-2 current density. Lindane was quickly oxidized by in-situ generated hydroxyl radicals, (M(^•OH)), formed from oxidation of water on the anode (M) surface following pseudo first-order reaction kinetics. Formation of chlorinated and hydroxylated intermediates and carboxylic acids during the treatment were identified and a plausible mineralization pathway of lindane by hydroxyl radicals was proposed.

Abatement of the antibiotic levofloxacin in a solar photoelectro-Fenton flow plant: Modeling the dissolved organic carbon concentration-time relationship

The degradation of solutions of the antibiotic levofloxacin (LVN) in sulfate medium at pH 3.0 has been investigated at pre-pilot scale by solar photoelectro-Fenton (SPEF) process. The flow plant included an FM01-LC filter-press cell equipped with a Ti|Pt anode and a three-dimensional-like air-diffusion cathode, connected to a compound parabolic collector as photoreactor and a continuous stirred tank under recirculation batch mode. The effect of volumetric flow rate on H₂O₂ electrogeneration from O₂ reduction was assessed. Then, the influence of initial LVN concentration and Fe²⁺ concentration as catalyst on dissolved organic carbon (DOC) removal was thoroughly investigated. LVN was gradually mineralized by SPEF process, with faster DOC abatement at 0.50 mM Fe²⁺, yielding 100% after 360 min at applied cathodic potential of -0.30 V|SHE. The high mineralization current efficiency (MCE) and low specific energy consumption (EC_DOC) revealed the extraordinary role of homogeneous hydroxyl radicals and natural UV light, which allowed the degradation of the antibiotic and its by-products with MCE values greater than 100%. Five cyclic by-products, N,N-diethylformamide and three short-chain linear carboxylic acids were detected by GC-MS and HPLC analyses. A parametric model to simulate the DOC decay versus electrolysis time was implemented for the SPEF pre-pilot flow plant, showing good agreement with experimental data.

Influence of chelation on the Fenton-based electrochemical degradation of herbicide tebuthiuron

This study describes the performance of electro-Fenton (EF) and photoelectro-Fenton (PEF) processes to degrade the herbicide tebuthiuron (TBH) in 0.050 M Na₂SO₄ at pH = 3.0. Experiments were performed in an undivided cell equipped with a boron-doped diamond (BDD) or Pt anode and an air-diffusion cathode that produces H₂O₂. Physisorbed hydroxyl radicals (M(OH)) generated from water oxidation at the anode and/or free OH formed from Fenton's reaction acted as main oxidants. All processes became much more effective using a BDD anode because of the higher oxidation power of BDD(OH). Sulfate and nitrate were the predominant ions released during TBH destruction. In both, EF and PEF treatments, two distinct kinetic regimes were observed, the first one corresponding to the oxidation of free TBH by OH and the second one to that of the Fe(III)-TBH complex by M(OH). The effect of Fe²⁺ and TBH concentrations on the kinetics of both regions has been examined. Moreover, a poor mineralization was reached with Pt anode, whereas almost total mineralization was attained by EF and PEF with BDD. Both processes showed analogous mineralization rates because the intermediates produced could not be photodegraded by UVA light. Gas chromatography-mass spectrometry analysis of electrolyzed solutions revealed the generation of eight heteroaromatics along with 1,3-dimethylurea, which have been included in a reaction pathway proposed for the initial degradation of TBH.

Electrochemical Fenton-based treatment of tetracaine in synthetic and urban wastewater using active and non-active anodes

The electrochemical degradation of tetracaine hydrochloride has been studied in urban wastewater. Treatments in simulated matrix with similar ionic composition as well as in 0.050 M Na₂SO₄ were comparatively performed. The cell contained an air-diffusion cathode for H₂O₂ electrogeneration and an anode selected among active Pt, IrO₂-based and RuO₂-based materials and non-active boron-doped diamond (BDD). Electrochemical oxidation with electrogenerated H₂O₂ (EO-H₂O₂), electro-Fenton (EF) and photoelectro-Fenton (PEF) were comparatively assessed at pH 3.0 and constant current density. The pharmaceutical and its byproducts were oxidized by OH formed from water oxidation at the anode surface and in the bulk from Fenton's reaction, which occurred upon addition of 0.50 mM Fe²⁺ in all media, along with active chlorine originated from the anodic oxidation of Cl^- contained in the simulated matrix and urban wastewater. The PEF process was the most powerful treatment regardless of the electrolyte composition, owing to the additional photolysis of intermediates by UVA radiation. The use of BDD led to greater mineralization compared to other anodes, being feasible the total removal of all organics from urban wastewater by PEF at long electrolysis time. Chlorinated products were largely recalcitrant when Pt, IrO₂-based or RuO₂-based anodes were used, whereas they were effectively destroyed by BDD(OH). Tetracaine decay always obeyed a pseudo-first-order kinetics, being slightly faster with the RuO₂-based anode in Cl^- media because of the higher amounts of active chlorine produced. Total nitrogen and concentrations of NH₄⁺, NO₃^-, ClO₃^-, ClO₄^- and active chlorine were determined to clarify the behavior of the different electrodes in PEF. Eight intermediates were identified by GC-MS and fumaric and oxalic acids were quantified as final carboxylic acids by ion-exclusion HPLC, allowing the proposal of a plausible reaction sequence for tetracaine mineralization by PEF in Cl^--containing medium.

Treatability of phenol-production wastewater: Rate constant and pathway of dimethyl phenyl carbinol oxidation by hydroxyl radicals

Phenol-production wastewater is difficult to treat biologically by aerobic processes to meet the effluent standard COD of 120 mg L^-1 because it contains several highly refractory aromatic pollutants, particularly dimethyl phenyl carbinol. Pretreatment revealed that dimethyl phenyl carbinol was slowly oxidized by molecular ozone; however, it readily reacted with hydroxyl radicals to yield acetophenone as a primary product. Acetophenone was further oxidized, first through five different pathways to form benzoic acid, phenyl glyoxalic acid, 4-4'-diacetyl biphenyl, and several hydroxylated aromatic compounds, and later to aliphatic carboxylic acids via ring cleavage. Regardless of system configuration (homogeneous vs heterogeneous), operating mode (batch vs continuous), and chemical concentration, the average intrinsic rate constants were 1.05 × 10¹⁰ and 9.29 × 10⁹ M^-1 s^-1 for dimethyl phenyl carbinol and acetophenone, respectively.

p-Nitrophenol degradation by electro-Fenton process: Pathway, kinetic model and optimization using central composite design

The chemical process scale-up, from lab studies to industrial production, is challenging and requires deep knowledge of the kinetic model and the reactions that take place in the system. This knowledge is also useful in order to be employed for the reactor design and the determination of the optimal operational conditions. In this study, a model substituted phenol such as p-nitrophenol was degraded by electro-Fenton process and the reaction products yielded along the treatment were recorded. The kinetic model was developed using Matlab software and was based on main reactions that occurred until total mineralization which allowed predicting the degradation pathway under this advanced oxidation process. The predicted concentration profiles of p-nitrophenol, their intermediates and by-products in electro-Fenton process were validated with experimental assays and the results were consistent. Finally, based on the developed kinetic model the degradation process was optimized using central composite design taking as key parameters the ferrous ion concentration and current density.

Sulfanilamide in solution and liposome vesicles; in vitro release and UV-stability studies

The main goal of this study was to develop a liposome formulation with sulfanilamide and to investigate the liposomes impact on its release and stability to the UV-A/UV-B and UV-C irradiation. Liposome dispersions with incorporated sulfanilamide were prepared by thin-film hydration method and liposomes role to the sulfanilamide release was investigated by using a dialysis method. Comparatively, sulfanilamide in phosphate buffer solution was subject to release study as well to the UV irradiation providing for the possibilities of kinetics analysis. In vitro drug release study demonstrated that 20% of sulfanilamide was released from liposomes within 1 h that is approximately twice as slower as in the case of dissolved sulfanilamide in phosphate buffer solution. The kinetic release process can be described by Korsmeyer–Peppas model and according to the value of diffusion release exponent it can be concluded that drug release mechanism is based on the phenomenon of diffusion. The sulfanilamide degradation in phosphate buffer solution and liposomes is related to the formation of UV-induced degradation products that are identified by UHPLC/MS analysis as: sulfanilic acid, aniline and benzidine. The UV-induced sulfanilamide degradation in the phosphate buffer solution and liposome vesicles fits the first- order kinetic model. The degradation rate constants are dependent on the involved UV photons energy input as well as sulfanilamide microenvironment. Liposome microenvironment provides better irradiation sulfanilamide stability. The obtained results suggest that liposomes might be promising carriers for delayed sulfanilamide delivery and may serve as a basis for further research.

Decolorization and degradation of reactive yellow HF aqueous solutions by electrochemical advanced oxidation processes

Textile manufacturing is the one responsible for water bodies' contamination through the discharge of colored wastes. This work presents the study of reactive yellow HF (RYHF) dye degradation under two different electrochemical advanced oxidation processes (EAOP), namely anodic oxidation (AO) and electro-Fenton (EF)/boron-doped diamond (BDD) process. For the AO, 100 and 300 mg/L solutions using Pt and BDD as anodes in a 100 mL stirred tank cell were used, with a supporting electrolyte of 0.05 mol/L of Na₂SO₄ at pH 3 under 30 and 50 mA/cm² current density. The EF/BDD process was carried out in a flow reactor at 4 and 7 L/min to degrade 100, 200, and 300 mg/L RYHF solutions under 50 and 80 mA/cm². UV-Vis determinations were used for decolorization evaluation, while high-performance liquid chromatography (HPLC) method provided information on dye degradation rate.