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6CCVD Research

Kinetic Insights and Process Selection for Electrochemical Remediation of Industrial Dye Effluents Using Mixed Electrode Systems

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2025-10-27
JournalProcesses
AuthorsCarmen Barcenas-Grangeno, Martín Pacheco‐Álvarez, Enric Brillas, Miguel A. Sandoval, Juan M. Peralta‐Hernández
InstitutionsUniversidad de Guanajuato, TecnolĂłgico Nacional de MĂ©xico
AnalysisFull AI Review Included

Kinetic Insights and Process Selection for Electrochemical Remediation

Section titled “Kinetic Insights and Process Selection for Electrochemical Remediation”

Executive Summary

Section titled “Executive Summary”

This study systematically compared three Electrochemical Advanced Oxidation Processes (EAOPs)—Anodic Oxidation (AO), Electro-Fenton (EF), and Photoelectro-Fenton (PEF)—using Boron-Doped Diamond (BDD) and Mixed-Metal Oxide (MMO) anodes for treating industrial dye mixtures.

  • Process Hierarchy: The optimal EAOP configuration is highly dependent on pollutant load and effluent composition (azo vs. anthraquinone dyes).
  • Dark Operation Benchmark: EF-BDD was confirmed as the most robust dark option, achieving fast decolorization (90% removal in 23 min) and significant mineralization (~70% COD removal) in the ternary mixture.
  • Photo-Assisted Superiority: PEF-MMO provided the fastest kinetics (ka = 0.136 min-1) and highest mineralization (~90% COD removal) for azo-rich effluents when UVA irradiation was available.
  • Electrode Mechanism: BDD anodes favor surface-bound hydroxyl radical (‱OH) attack (best at low loads), while MMO anodes benefit significantly from photo-assisted bulk Fenton chemistry due to strong adsorption and photolysis of Fe(III) complexes.
  • Efficiency Metric: Decolorization alone overestimates efficiency. Integrating COD removal and energy consumption (ECCOD) analysis is critical for identifying sustainable processes.
  • Practical Guideline: EF-BDD is recommended as the baseline technology; PEF-MMO is the preferred, cost-efficient alternative when sunlight or artificial UVA is harnessable, particularly for effluents rich in UVA-absorbing azo dyes.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Reactor Volume250mLBatch reactor volume
Operating Temperature25 ± 1°CThermostated condition
Supporting Electrolyte50mMNa2SO4 concentration
Initial pH3.0-Standard Fenton condition
Applied Current Density (j)20, 40, or 60mA cm-2Constant current range tested
Anode MaterialsBDD, MMO-BDD: Boron-Doped Diamond; MMO: Ti/IrO2-SnO2-Sb2O5
Fe2+ Concentration (EF/PEF)0.5mMFerrous sulfate heptahydrate addition
UVA Irradiance7.5 ± 0.3W m-2Delivered by 6 W black-light lamp
Air Bubbling Rate1.5L min-1Ensures oxygen availability for H2O2 generation
Max Decolorization Rate (ka)0.136min-1Ternary mixture, PEF-MMO, 60 mA cm-2
Time for 90% Decolorization22minTernary mixture, PEF-MMO
Max COD Removal (Ternary)~90%PEF-MMO, 60 min run
Energy Consumption (ECCOD)0.08kWh (g COD)-1PEF-MMO at 60 min (200 mg L-1 load)

Key Methodologies

Section titled “Key Methodologies”
  1. Electrode Systems: Experiments utilized six configurations encompassing AO, EF, and PEF. Anodes were BDD or synthesized MMO (Ti/IrO2-SnO2-Sb2O5). Cathodes were Graphite (AO) or BDD/MMO (EF/PEF).
  2. Electrochemical Operation: A constant current density (20-60 mA cm-2) was applied. All electrodes had a 4 cm2 surface area and were separated by 1.0 cm.
  3. Fenton Conditions: EF and PEF processes required 0.5 mM FeSO4·7H2O addition and continuous air bubbling (1.5 L min-1) to ensure in situ H2O2 electrogeneration at the cathode.
  4. Photo-Assistance: PEF utilized a 6 W UVA lamp (lambdamax ~ 360 nm) positioned 2.5 cm above the liquid surface, delivering 7.5 W m-2 irradiance to drive Fe3+ regeneration.
  5. Kinetic Analysis: Decolorization was monitored by UV-Vis spectrophotometry. Apparent rate constants (ka) were calculated assuming pseudo-first-order kinetics (Ln(A0/A) = kat), requiring a correlation coefficient (R2) > 0.95 for validation.
  6. Mineralization Assessment: Chemical Oxygen Demand (COD) was measured using the closed reflux colorimetric method for representative, mechanistically informative conditions to quantify true organic load reduction.
  7. Energy Efficiency: Performance was normalized using the energy consumption per unit mass of COD removed (ECCOD), accounting for both electrical energy input (Ecell I t) and UVA lamp power (PUVA t).

Commercial Applications

Section titled “Commercial Applications”

The findings are directly applicable to industrial sectors requiring robust and energy-efficient treatment of complex, recalcitrant organic wastewater streams.

  • Wastewater Treatment (Textile/Dyeing): Direct application for treating effluents containing complex azo (Coriasol Red CB, Brown RBH) and anthraquinone (Blue VT) dyes.
  • Advanced Electrode Manufacturing: Drives demand for high-performance, long-lifetime BDD anodes (for robust dark EF) and specialized MMO anodes (for efficient PEF under light).
  • Resource Recovery and Sustainability: Supports the integration of EAOPs into circular economy models, enabling water reuse in textile processes and potential valorization of iron-rich sludge residues.
  • Chemical and Pharmaceutical Industries: Applicable for the degradation of other recalcitrant organic pollutants that are resistant to conventional biological treatments.
  • Decentralized Systems: The modular nature and compatibility with renewable energy sources (solar-powered PEF) make these EAOPs suitable for decentralized industrial water management.
View Original Abstract

The discharge of dye-laden effluents remains an environmental challenge since conventional treatments remove color but not the organic load. This study systematically compared anodic oxidation (AO), electro-Fenton (EF), and photoelectro-Fenton (PEF) processes for three representative industrial dyes, such as Coriasol Red CB, Brown RBH, and Blue VT, and their ternary mixture, using boron-doped diamond (BDD) and Ti/IrO2-SnO2-Sb2O5 (MMO) anodes. Experiments were conducted in a batch reactor with 50 mM Na2SO4 at pH = 3.0 and current densities of 20-60 mA cm−2. Kinetic analysis showed that AO-BDD was most effective at low pollutant loads, EF-BDD became superior at medium loads due to efficient H2O2 electrogeneration, and PEF-MMO dominated at higher loads by fast UVA photolysis of surface Fe(OH)2+ complexes. In a ternary mixture of 120 mg L−1 of dyes, EF-BDD and PEF-MMO achieved >98% decolorization in 22-23 min with pseudo-first-order rate constants of 0.111-0.136 min−1, whereas AO processes remained slower. COD assays revealed partial mineralization of 60-80%, with EF-BDD providing the most consistent reduction and PEF-MMO minimizing treatment time. These findings confirm that decolorization overestimates efficiency, and electrode selection must be tailored to dye structure and effluent composition. Process selection rules allow us to conclude that EF-BDD is the best robust dark option, and PEF-MMO, when UVA is available, offers practical guidelines for cost-effective electrochemical treatment of textile wastewater.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2025 - A critical review on textile dye-containing wastewater: Ecotoxicity, health risks, and remediation strategies for environmental safety [Crossref]
  2. 2025 - Insights into the synthetic dye contamination in textile wastewater: Impacts on aquatic ecosystems and human health, and eco-friendly remediation strategies for environmental sustainability [Crossref]
  3. 2024 - A review of history, properties, classification, applications and challenges of natural and synthetic dyes [Crossref]
  4. 2020 - A review on classifications, recent synthesis and applications of real industrial dye [Crossref]
  5. 2022 - Miscellaneous azo dyes: A comprehensive review on recent advancements in biological and industrial applications [Crossref]
  6. 2022 - A review on treatment technologies for printing and dyeing wastewater (PDW) [Crossref]
  7. 2023 - Current perspectives, recent advancements, and efficiencies of various dye-containing wastewater treatment technologies [Crossref]
  8. 2025 - Recent trends in physio-chemo technologies and their role in dyes removal: Effectiveness, benefits, and limitations [Crossref]
  9. 2022 - Review on effect of different type of dyes on advanced oxidation processes (AOPs) for textile color removal [Crossref]

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