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

At a Glance

Metadata	Details
Publication Date	2025-09-29
Journal	Preprints.org
Authors	Carmen Barcenas-Granjeno, Martín Pacheco‐Álvarez, Enric Brillas, Miguel A. Sandoval, Juan M. Peralta‐Hernández
Analysis	Full AI Review Included

Technical Documentation & Analysis: MPCVD Diamond for Advanced Oxidation Processes

Executive Summary

This study rigorously compares electrochemical advanced oxidation processes (EAOPs) for treating complex industrial dye effluents, confirming the critical role of Boron-Doped Diamond (BDD) electrodes in achieving high mineralization and kinetic efficiency.

BDD Superiority in AO: Boron-Doped Diamond (BDD) anodes consistently demonstrated superior performance in Anodic Oxidation (AO) due to their high oxygen evolution overpotential, maximizing the flux of surface-bound hydroxyl radicals (BDD(•OH)).
Robust Dark Treatment: The Electro-Fenton (EF) process, specifically utilizing BDD cathodes for enhanced H₂O₂ electrogeneration, was identified as the most robust dark option for achieving significant Chemical Oxygen Demand (COD) removal (up to 70% in mixtures).
Kinetic Dominance in Mixtures: For complex ternary dye mixtures (120 mg L^-1), EF-BDD achieved 99.6% decolorization in 23 minutes (k_a = 0.1105 min^-1), significantly outperforming AO configurations constrained by competitive adsorption.
Photo-Assisted Efficiency: Photoelectro-Fenton (PEF) using Mixed Metal Oxide (MMO) anodes achieved the fastest kinetics (k_a = 0.136 min^-1) and highest energy efficiency when UVA irradiation was available, highlighting the synergy between photon input and electrode material.
Material Selection is Key: The findings underscore that electrode material selection (BDD vs. MMO) must be precisely tailored to the pollutant load and molecular structure (azo vs. anthraquinone) to optimize surface-driven versus bulk-radical oxidation pathways.
6CCVD Value Proposition: This research validates 6CCVD’s high-quality BDD material as essential for developing scalable, high-efficiency EAOP reactors for textile and industrial wastewater remediation.

Technical Specifications

The following hard data points were extracted from the experimental setup and results, focusing on the optimal performance parameters achieved using BDD electrodes.

Parameter	Value	Unit	Context
Anode Materials Tested	BDD, MMO (Ti/IrO₂-SnO₂-Sb₂O₅)	N/A	EAOP comparison
Cathode Materials Tested	BDD, Graphite (G), MMO	N/A	H₂O₂ electrogeneration
Optimal Current Density (j)	60	mA cm^-2	Used for high-load/mixture testing
Supporting Electrolyte Concentration	50	mM	Na₂SO₄
Initial pH	3.0	N/A	Standard for Fenton chemistry
Decolorization Efficiency (Ternary Mix)	>98	%	Achieved by EF-BDD and PEF-MMO
Time to 90% Decolorization (EF-BDD)	23	min	Ternary mixture (120 mg L^-1)
Pseudo-First Order Rate Constant (EF-BDD)	0.1105	min^-1	Most robust dark process for mixtures
COD Removal Efficiency (EF-BDD)	~70	%	Ternary mixture (200 mg L^-1, 60 min)
UVA Lamp Wavelength (λ_max)	≈ 360	nm	Photoelectro-Fenton (PEF) irradiation
Operating Temperature	25 ± 1	°C	Thermostated batch reactor

Key Methodologies

The electrochemical advanced oxidation processes (EAOPs) were systematically compared under strictly controlled batch conditions to isolate the performance differences between electrode materials and radical generation pathways.

Solution Preparation: All solutions were prepared using 50 mM Na₂SO₄ supporting electrolyte, adjusted to pH 3.0 using H₂SO₄. For EF and PEF assays, 0.5 mM FeSO₄·7H₂O was added as the catalyst source.
Reactor Setup: Experiments were conducted in a thermostated 250 mL batch reactor maintained at 25 ± 1 °C with continuous magnetic stirring (500 rpm).
Electrode Configuration: Six configurations were tested (AO, EF, PEF) using BDD/Graphite, MMO/Graphite, BDD/BDD, and MMO/MMO pairs. All electrodes had a geometric surface area of 4 cm² and a 1.0 cm interelectrode distance.
Current Application: A constant current density (j) was applied, ranging from 20 to 60 mA cm^-2, using a BK Precision 1688B power source.
Oxygen Supply: Air was continuously bubbled through the solution at 1.5 L min^-1 to ensure sufficient dissolved oxygen for in situ H₂O₂ electrogeneration at the cathode (Eq. 3).
Photo-Assisted Setup (PEF): For PEF, the reactor was irradiated using a 6 W black-light UVA lamp (emission band 355-370 nm) positioned 2.5 cm above the liquid surface, delivering an irradiance of 7.5 W m^-2.
Analytical Metrics: Decolorization kinetics (k_a) were monitored via UV-Vis spectrophotometry, assuming pseudo-first-order kinetics. Mineralization was assessed via Chemical Oxygen Demand (COD) decay using the closed reflux colorimetric method.

6CCVD Solutions & Capabilities

This research confirms that Boron-Doped Diamond (BDD) is the material of choice for high-efficiency, high-mineralization electrochemical wastewater treatment. 6CCVD provides the necessary MPCVD diamond materials and customization services required to replicate this research at scale and optimize industrial EAOP deployment.

Research Requirement	6CCVD Solution & Capability	Technical Advantage
Applicable Materials	Heavy Boron-Doped Diamond (BDD) Plates/Wafers.	Our BDD material ensures the highest density of physisorbed hydroxyl radicals (BDD(•OH)), critical for the superior AO performance observed, especially for anthraquinone dyes (Blue VT).
Cathode Material Optimization	Custom BDD Films (0.1 µm - 500 µm thickness).	Utilizing BDD as a cathode significantly enhances H₂O₂ electrogeneration (Eq. 3), making EF-BDD the most robust dark process for high COD removal in complex effluents.
Scale-Up and Dimensions	Polycrystalline Diamond (PCD) Wafers up to 125 mm.	The study used 4 cm² electrodes. 6CCVD enables immediate scale-up to pilot and industrial systems, offering custom plates and wafers up to 125 mm in diameter, far exceeding typical lab-scale dimensions.
Electrode Integration	Custom Metalization Services (Ti, Pt, Au, Pd, W, Cu).	We provide in-house metalization capabilities to create robust, low-resistance electrical contacts, essential for integrating BDD anodes and cathodes into complex mixed electrode systems (e.g., for EF and PEF reactors).
Surface Finish	High-Quality Polishing (Ra < 5 nm for PCD).	Consistent surface quality is vital for uniform current distribution and reproducible radical generation. Our polishing services ensure optimal performance and longevity of the BDD electrodes.
Engineering Support	In-House PhD Team Consultation.	6CCVD’s experts can assist researchers and engineers in selecting the optimal BDD doping level and thickness required for specific EAOP applications (AO, EF, PEF) targeting high COD removal and energy efficiency in complex wastewater matrices.

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 &gt;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 concluding 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/10.20944/preprints202509.2362.v1