Simultaneous Electrochemical Generation of Ferrate and Oxygen Radicals to Blue BR Dye Degradation

At a Glance

Metadata	Details
Publication Date	2020-06-28
Journal	Processes
Authors	Mauricio Chiliquinga, Patricio J. Espinoza-Montero, Oscar M. Rodriguez, Alain R. Picos-Benítez, Erick R. Bandala
Institutions	Pontificia Universidad Católica del Ecuador, Desert Research Institute
Citations	12
Analysis	Full AI Review Included

Technical Documentation: Advanced Oxidation Processes (AOP) using Boron-Doped Diamond (BDD) Anodes

Reference Paper: Simultaneous Electrochemical Generation of Ferrate and Oxygen Radicals to Blue BR Dye Degradation

Executive Summary

6CCVD analyzes this research demonstrating the superior performance of Boron-Doped Diamond (BDD) anodes in Advanced Oxidation Processes (AOP) for wastewater treatment.

Synergistic Oxidation: The BDD anode successfully facilitated the simultaneous in situ generation of highly reactive hydroxyl radicals (•OH) and powerful Ferrate ions [Fe(VI)].
High Efficiency: Optimal conditions achieved 98% Blue BR dye discoloration in 60 minutes, significantly outperforming Electro-oxidation (EOx) alone (78% discoloration).
Mineralization Capability: The combined EOx/[Fe(VI)] process resulted in a 61% Chemical Oxygen Demand (COD) reduction, nearly doubling the efficiency of EOx alone (37% COD reduction).
Electrolyte Optimization: Using 0.05 M Na₂SO₄ as the supporting electrolyte proved critical, yielding degradation rates approximately 3.5 times faster than 0.1 M HClO₄.
Low Potential Ferrate Generation: The BDD surface enabled the overoxidation of Fe(II) to the highly desired Fe(VI) species at a relatively low potential (0.78 V vs. Ag/AgCl) in the sulfate medium.
Byproduct Control: The simultaneous generation of oxidants rapidly degraded reaction intermediates (specifically oxalic acid), minimizing the accumulation of toxic byproducts.

Technical Specifications

The following hard data points were extracted from the electrochemical degradation study:

Parameter	Value	Unit	Context
Anode Material	Boron-Doped Diamond (BDD)	N/A	Working Electrode
Optimal Current Density (j)	30	mA cm^-2	Highest efficiency for discoloration and COD reduction
Optimal FeSO₄ Concentration	12	mM	Ferrate precursor concentration
Optimal Electrolyte	0.05 M Na₂SO₄	N/A	Adjusted to pH 3
BDD Anode Area (EOx)	2.5	cm²	Used for degradation assays
Max BBR Discoloration	98	%	Achieved in 60 min using optimal conditions
Max COD Reduction	61	%	Achieved in 90 min using optimal conditions
EOx Alone Discoloration	78	%	Achieved in 60 min at 30 mA cm^-2
EOx Alone COD Reduction	37	%	Achieved in 90 min
Fe(VI) Generation Potential (Na₂SO₄)	0.78	V vs. Ag/AgCl	Overoxidation potential of Fe(II) to Fe(VI)
Reaction Rate Constant (k₁)	0.0703	min^-1	Highest rate achieved (30 mA cm^-2, 12 mM FeSO₄)

Key Methodologies

The experimental approach focused on characterizing the BDD electrode performance and optimizing the simultaneous generation of oxidants under galvanostatic control.

Electrode Configuration: Experiments utilized a three-electrode cell setup. The working electrode was a BDD plate (0.5 cm² for CV, 2.5 cm² for EOx), paired with a Platinum (Pt) wire counter electrode and an Ag/AgCl reference electrode.
Electrochemical Characterization (CV): Cyclic Voltammetry (CV) was performed to confirm the redox behavior of FeSO₄ and the in situ electrogeneration of [Fe(VI)] on the BDD surface in both 0.1 M HClO₄ and 0.05 M Na₂SO₄ media.
Galvanostatic Operation: Discoloration and degradation assays were conducted in galvanostatic mode in a 100 mL reactor, testing current densities of 7, 15, and 30 mA cm^-2.
Precursor Dosing: Ferrous sulfate (FeSO₄) was added at concentrations of 1 mM, 6 mM, and 12 mM to evaluate its effect on ferrate generation and overall dye degradation kinetics.
Analytical Monitoring: Degradation kinetics were modeled using pseudo-first-order kinetics (Ln(A₀/A_t) = kt). COD reduction was measured using Standard Methods (5220D), and byproduct (oxalic acid) evolution was tracked using Ion-Exclusion High-Performance Liquid Chromatography (HPLC).

6CCVD Solutions & Capabilities

This research highlights the critical role of high-quality, stable Boron-Doped Diamond (BDD) electrodes in achieving highly efficient AOP for industrial wastewater treatment. 6CCVD is uniquely positioned to supply the materials required to replicate, scale, and advance this technology.

Applicable Materials

To achieve the high current densities (up to 30 mA cm^-2) and chemical stability required for simultaneous radical and ferrate generation, researchers need robust, high-purity BDD.

6CCVD Material Solution	Specification Relevance	Application Focus
Heavy Boron-Doped PCD Wafers	High doping concentration ensures low resistivity and wide electrochemical window, essential for high overpotential oxygen radical (•OH) generation and Fe(VI) synthesis.	Electrochemical AOP, Ferrate Generation, Industrial Effluent Treatment
Optical Grade SCD (Thin Film)	SCD films (0.1 µm to 500 µm) offer ultra-low surface roughness (Ra < 1 nm), minimizing adsorption effects observed in CV studies.	Fundamental electrochemistry, CV studies, High-precision sensor applications
Custom Substrates	6CCVD provides BDD films deposited on various substrates (e.g., Si, Nb, W) tailored for specific reactor designs and thermal requirements.	Flow reactors, Pilot-scale systems, High-temperature operation

Customization Potential for Scale-Up

The paper utilized small BDD electrodes (2.5 cm²). Scaling this technology to industrial flow reactors requires large-area, custom-designed electrodes, a core capability of 6CCVD.

Large Format Electrodes: 6CCVD manufactures Polycrystalline Diamond (PCD) plates and wafers up to 125 mm in diameter, enabling significant scale-up of the EOx/[Fe(VI)] process.
Custom Dimensions and Geometry: We offer precision laser cutting and shaping services to produce custom electrode geometries (e.g., rods, meshes, or specific tank dimensions) required for optimized mass transfer in industrial reactors.
Integrated Metalization: The experiment required a Platinum (Pt) counter electrode. 6CCVD provides in-house metalization services (Au, Pt, Pd, Ti, W, Cu) for creating robust electrical contacts or integrating counter/reference electrodes directly onto the diamond substrate or housing.
Surface Finishing: We provide polishing services to achieve ultra-smooth surfaces (Ra < 5 nm for inch-size PCD), crucial for maintaining consistent electrochemical activity and minimizing fouling in complex wastewater matrices.

Engineering Support

The successful implementation of simultaneous EOx/[Fe(VI)] requires precise control over material properties, doping levels, and reactor design.

AOP Optimization: 6CCVD’s in-house team of PhD material scientists specializes in optimizing BDD properties (doping density, sp²/sp³ ratio) to maximize the efficiency of hydroxyl radical and ferrate generation for specific Advanced Oxidation Process (AOP) applications.
Material Selection Consultation: We provide expert guidance on selecting the optimal BDD thickness (SCD or PCD) and substrate material to ensure longevity and performance under high current density and corrosive acidic/sulfate environments.
Global Logistics: We ensure reliable global delivery of high-value diamond materials via DDU (default) or DDP shipping terms.

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

View Original Abstract

In this study, electro-oxidation (EOx) and in situ generation of ferrate ions [Fe(VI)] were tested to treat water contaminated with Blue BR dye (BBR) using a boron-doped diamond (BDD) anode. Two electrolytic media (0.1 M HClO4 and 0.05 M Na2SO4) were evaluated for the BDD, which simultaneously produced oxygen radicals (•OH) and [Fe(VI)]. The generation of [Fe(VI)] was characterized by cyclic voltammetry (CV) and the effect of different current intensity values (e.g., 7 mA cm−2, 15 mA cm−2, and 30 mA cm−2) was assessed during BBR degradation tests. The discoloration of BBR was followed by UV-Vis spectrophotometry. When the EOx process was used alone, only 78% BBR discoloration was achieved. The best electrochemical discoloration conditions were found using 0.05 M Na2SO4 and 30 mA cm−2. Using these conditions, overall BBR discoloration values up to 98%, 95%, and 87% with 12 mM, 6 mM, and 1 mM of FeSO4, respectively, were achieved. In the case of chemical oxygen demand (COD) reduction, the EOx process showed only a 37% COD reduction, whereas combining [Fe(VI)] generation using 12 mM of FeSO4 achieved an up to 61% COD reduction after 90 min. The evolution of reaction byproducts (oxalic acid) was performed using liquid chromatography analysis.

Tech Support

Original Source

DOI: https://doi.org/10.3390/pr8070753

References

2018 - Comparative study for degradation of industrial dyes by electrochemical advanced oxidation processes with BDD anode in a laboratory stirred tank reactor [Crossref]
2009 - On-line production of ferrate with an electrochemical method and its potential application for wastewater treatment—A review [Crossref]
2004 - Effect of sp2-Bonded Nondiamond Carbon Impurity on the Response of Boron-Doped Polycrystalline Diamond Thin-Film Electrodes [Crossref]
2018 - Electrosynthesis of ferrate in a batch reactor at neutral conditions for drinking water applications [Crossref]
2018 - Degradation of ferrate species produced electrochemically for use in drinking water treatment applications [Crossref]
2019 - Contaminants of emerging concern removal from real wastewater by UV/free chlorine process: A comparison with solar/free chlorine and UV/H2O2 at pilot scale [Crossref]
2006 - Study on Fe (VI) species as a disinfectant: Quantitative evaluation and modeling for inactivating Escherichia coli [Crossref]
2018 - Abatement of the antibiotic levofloxacin in a solar photoelectro-Fenton flow plant: Modeling the dissolved organic carbon concentration-time relationship [Crossref]
2019 - Electrochemical oxidation of dibenzothiophene compounds on BDD electrode in acetonitrile-water medium [Crossref]