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

At a Glance

Metadata	Details
Publication Date	2025-10-27
Journal	Processes
Authors	Carmen Barcenas-Grangeno, Martín Pacheco‐Álvarez, Enric Brillas, Miguel A. Sandoval, Juan M. Peralta‐Hernández
Institutions	Universitat de Barcelona, Tecnológico Nacional de México
Analysis	Full AI Review Included

Technical Documentation & Analysis: MPCVD Diamond for Advanced Electrochemical Oxidation (EAOPs)

Reference Paper: Kinetic Insights and Process Selection for Electrochemical Remediation of Industrial Dye Effluents Using Mixed Electrode Systems (Processes 2025, 13, 3439)

Executive Summary

This research validates the critical role of Boron-Doped Diamond (BDD) electrodes in achieving rapid decolorization and high mineralization efficiency for complex industrial dye effluents using Electrochemical Advanced Oxidation Processes (EAOPs).

Superior Dark Process: Electro-Fenton (EF) using BDD anodes and cathodes (EF-BDD) was confirmed as the most robust dark option, achieving 99.6% decolorization of a complex ternary mixture in 23 minutes and 70% Chemical Oxygen Demand (COD) removal in 60 minutes.
High Radical Flux: Anodic Oxidation (AO) using BDD anodes (AO-BDD) demonstrated superior kinetics at low pollutant loads due to the high surface flux of physisorbed BDD(•OH) radicals, leveraging diamond’s wide oxygen evolution overpotential.
Enhanced H₂O₂ Generation: Utilizing BDD as the cathode significantly enhanced H₂O₂ electrogeneration, a key precursor for the highly efficient homogeneous Fenton reaction in the bulk solution.
Process Selection Rules: The study provides clear guidelines: AO-BDD is optimal for low loads, EF-BDD dominates as the most reliable dark process for medium/high loads, and Photoelectro-Fenton (PEF) with Mixed-Metal Oxide (MMO) is only superior when UVA irradiation is available for azo-rich effluents.
Mineralization Confirmation: COD analysis confirmed that decolorization alone overestimates efficiency; BDD-based EF provided the most consistent and significant COD reduction among the dark processes.
Scalability Validation: Experiments were conducted under controlled, pilot-scale relevant conditions (250 mL batch reactor, high current densities up to 60 mA cm^-2), confirming the practical viability of BDD for industrial wastewater treatment.

Technical Specifications

The following hard data points were extracted from the experimental setup and the best-performing BDD configuration (EF-BDD) for the ternary dye mixture (120 mg L^-1).

Parameter	Value	Unit	Context
Anode Material	Boron-Doped Diamond (BDD)	N/A	Anodic Oxidation (AO) & Electro-Fenton (EF)
Cathode Material	BDD or Graphite (G)	N/A	EF-BDD configuration used BDD cathode
Electrode Area	4	cm²	Geometric surface area
Interelectrode Distance	1.0	cm	Fixed reactor geometry
Current Density ($j$)	20, 40, 60	mA cm^-2	Range tested; 60 mA cm^-2 used for mixture
Electrolyte Concentration	50	mM	Na₂SO₄ supporting electrolyte
Initial pH	3.0	N/A	Adjusted with H₂SO₄
Temperature	25 ± 1	°C	Thermostated batch reactor
Fe²⁺ Concentration (EF/PEF)	0.5	mM	Ferrous sulfate heptahydrate
Air Flow Rate	1.5	L min^-1	Continuous bubbling for O₂ availability
Best Decolorization Rate ($k_{a}$)	0.1105	min^-1	EF-BDD, Ternary Mixture (120 mg L^-1)
Time to 90% Decolorization	23	min	EF-BDD, Ternary Mixture
COD Removal Efficiency	~70	%	EF-BDD, Ternary Mixture (60 min)
UVA Irradiance (PEF only)	7.5 ± 0.3	W m^-2	Black-light lamp ($\lambda_{max}$ $\approx$ 360 nm)

Key Methodologies

The systematic comparison of AO, EF, and PEF processes utilized strictly controlled electrochemical and hydrodynamic conditions to isolate the effects of electrode material and radical generation pathway.

Electrode Configurations: Six configurations were tested, including BDD/Graphite (AO), BDD/BDD (EF), and BDD/MMO (PEF), ensuring BDD was evaluated as both an anode (for •OH generation) and a cathode (for H₂O₂ generation).
Electrochemical Control: A constant current density ($j$) was applied (20, 40, or 60 mA cm^-2) using a precision power source, ensuring reproducible radical generation rates.
Fenton Conditions: EF and PEF assays maintained a fixed initial Fe²⁺ concentration (0.5 mM) and continuous aeration (1.5 L min^-1) to guarantee stable Fenton operating conditions and oxygen availability for in situ H₂O₂ production.
Photo-Assistance (PEF): UVA irradiation (6 W lamp, 7.5 W m^-2) was positioned 2.5 cm above the liquid surface to enable photo-assisted regeneration of Fe²⁺ and photolysis of intermediates.
Kinetic Analysis: Decolorization kinetics were monitored via UV-Vis spectrophotometry and fitted to pseudo-first-order kinetics (R² > 0.95 required).
Mineralization Assessment: True process efficiency was determined by measuring Chemical Oxygen Demand (COD) decay using the closed reflux colorimetric method, providing a metric for mineralization (organic load removal).
Energy Efficiency Normalization: Energy consumption was normalized against COD removed (EC_COD, kWh(g COD)^-1) to provide a cost-effective comparison of sustainable processes.

6CCVD Solutions & Capabilities

The findings of this research strongly support the use of 6CCVD’s high-quality MPCVD Boron-Doped Diamond (BDD) for industrial wastewater remediation, particularly in high-demand, complex effluent scenarios.

Applicable Materials

To replicate and extend the superior performance demonstrated by the EF-BDD configuration, 6CCVD recommends the following materials:

Heavy Boron-Doped Polycrystalline Diamond (PCD-BDD): Required for the anode material to maximize the oxygen evolution overpotential, ensuring the highest flux of BDD(•OH) radicals for direct anodic oxidation and robust performance under high current density (up to 60 mA cm^-2).
Polycrystalline Diamond (PCD) or BDD Cathodes: Essential for maximizing H₂O₂ electrogeneration via the two-electron reduction of dissolved O₂ (Equation 3, Page 6), which is critical for the superior bulk oxidation achieved in the EF-BDD process.

Customization Potential

The study utilized small-scale electrodes (4 cm²). 6CCVD’s manufacturing capabilities directly address the need for industrial scalability and customized reactor design:

Research Requirement	6CCVD Capability	Sales Advantage
Electrode Size (4 cm²)	Plates/wafers up to 125 mm (PCD)	Enables direct scale-up from lab-scale to pilot and industrial flow reactors.
Electrode Thickness	SCD/PCD thickness from 0.1 µm up to 500 µm	Custom thickness allows optimization of conductivity, mechanical stability, and cost efficiency for specific current density requirements.
Metal Contacts/Mounting	Internal metalization capability: Au, Pt, Pd, Ti, W, Cu	We provide electrodes ready for integration, including custom metal contacts (e.g., Ti/Pt/Au) required for robust electrical connection in corrosive EAOP environments.
Surface Finish	Polishing capability: Ra < 5 nm (Inch-size PCD)	While BDD anodes are often used unpolished, 6CCVD can provide ultra-smooth surfaces for research requiring specific surface chemistry or reduced fouling.
Substrate Options	Substrates up to 10 mm thick	Custom substrate materials and thicknesses ensure mechanical integrity for large-format electrodes used in industrial cells.

Engineering Support

The paper highlights a critical mechanistic crossover: AO-BDD dominates at low loads, while EF-BDD dominates at high loads and in complex mixtures. PEF-MMO is only superior under specific UVA irradiation conditions for azo dyes.

6CCVD’s in-house PhD team specializes in correlating material properties (boron doping level, surface termination, and morphology) with specific EAOP performance metrics (e.g., $k_{a}$, EC_COD). We offer consultation services to assist engineers and scientists in:

Material Selection: Tailoring the optimal BDD material (doping level and thickness) based on the target effluent composition (azo vs. anthraquinone) and required operational mode (AO, EF, or PEF).
Process Optimization: Providing guidance on integrating BDD electrodes into flow systems, optimizing current density, and maximizing energy efficiency (EC_COD) for industrial dye wastewater treatment projects.
Global Logistics: Ensuring reliable, global shipping (DDU default, DDP available) to maintain project timelines worldwide.

Call to Action: For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

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

Original Source

DOI: https://doi.org/10.3390/pr13113439

References

2025 - A critical review on textile dye-containing wastewater: Ecotoxicity, health risks, and remediation strategies for environmental safety [Crossref]
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]
2024 - A review of history, properties, classification, applications and challenges of natural and synthetic dyes [Crossref]
2020 - A review on classifications, recent synthesis and applications of real industrial dye [Crossref]
2022 - Miscellaneous azo dyes: A comprehensive review on recent advancements in biological and industrial applications [Crossref]
2022 - A review on treatment technologies for printing and dyeing wastewater (PDW) [Crossref]
2023 - Current perspectives, recent advancements, and efficiencies of various dye-containing wastewater treatment technologies [Crossref]
2025 - Recent trends in physio-chemo technologies and their role in dyes removal: Effectiveness, benefits, and limitations [Crossref]
2022 - Review on effect of different type of dyes on advanced oxidation processes (AOPs) for textile color removal [Crossref]