On the Degradation of 17-β Estradiol Using Boron Doped Diamond Electrodes

At a Glance

Metadata	Details
Publication Date	2020-06-19
Journal	Processes
Authors	Sandra Maldonado, Manuel A. Rodrigo, Pablo Cañizares, G. Roa, C. Barrera
Institutions	University of Castilla-La Mancha, Universidad Autónoma del Estado de México
Citations	13
Analysis	Full AI Review Included

Technical Documentation & Analysis: Boron Doped Diamond for Selective Electrochemical Oxidation

Executive Summary

This research validates the critical role of Boron Doped Diamond (BDD) electrodes in Advanced Oxidation Processes (AOPs) for treating highly complex and hazardous wastewater streams, specifically targeting endocrine-disrupting compounds (EDCs) like 17ß-estradiol.

High Efficiency Degradation: Complete depletion of 17ß-estradiol (E2) was achieved in synthetic urine/methanol mixtures using exceptionally low current charges (in the best case, less than 7 kAh·m^-3).
Selective Oxidation Potential: The study confirms that BDD anodes enable selective oxidation of E2 over less hazardous compounds (uric acid) by promoting direct electrochemical processes at the anode surface.
Optimal Conditions Identified: Selective removal is favored under conditions of low current density (20 mA·cm^-2) and high flowrate, which encourages direct oxidation rather than non-selective radical-mediated processes.
Material Quality Validation: The successful results rely on high-quality BDD films (2.83 µm thickness, 500 mg·dm^-3 boron content, sp³/sp² ratio of 217), underscoring the necessity of high-purity MPCVD diamond for industrial AOP applications.
Industrial Relevance: This methodology opens pathways for developing cost-effective, selective pre-treatment technologies for hospital and municipal wastewater, reducing hazardousness prior to cheaper biological treatments.

Technical Specifications

The following hard data points were extracted from the experimental setup and results, highlighting the performance metrics achieved using BDD anodes.

Parameter	Value	Unit	Context
Anode Material	Boron Doped Diamond (BDD)	N/A	Diacell® cell configuration
Electrode Area	78.54	cm²	Total electrodic area used
BDD Film Thickness	2.83	µm	Diamond coating specification
Boron Doping Concentration	500	mg·dm^-3	Boron content in the diamond coating
sp³/sp² Ratio	217	N/A	High quality diamond coating metric
Current Density (J) Range	20 - 100	mA·cm^-2	Galvanostatic operation range
Flowrate (F) Range	6.77 - 12.833	mL·s^-1	Recirculation flowrates tested
E2 Initial Concentration	10	mg·L^-1	Target pollutant concentration
Minimum Charge for E2 Depletion	< 7	kAh·m^-3	Achieved under optimal conditions
E2 Mineralization Electrons (z)	92	e^-	Theoretical electrons for full oxidation to CO₂
Optimal Selectivity Condition	Low J, High F	N/A	Favors direct oxidation of E2 over uric acid

Key Methodologies

The experiment utilized a recirculating electrochemical system under galvanostatic control to evaluate the degradation kinetics of 17ß-estradiol (E2) and uric acid (UA) in a complex organic matrix.

Electrochemical Setup: A Diacell® reactor equipped with BDD anodes and cathodes was connected to a 1 L glass tank, operating in a recirculating flow system.
Electrolyte Preparation: Synthetic urine (containing high concentrations of urea, salts, and uric acid) was mixed with methanol. Methanol served as a solvent for E2 desorption (in the context of a pre-concentration strategy) and acted as a hydroxyl radical scavenger.
Operational Control: Experiments were conducted under galvanostatic conditions, systematically varying two primary parameters:
- Current Density (J): Ranged from 20 mA·cm^-2 (soft oxidation) to 100 mA·cm^-2 (radical-mediated oxidation).
- Flowrate (F): Varied to assess the influence on mass transport limitations and residence time.
Kinetic Analysis: Degradation data for E2 and UA were fitted to pseudo-first-order kinetic models. The ratio of kinetic constants (k₁/k₂) was used to quantify the oxidizability and selectivity of E2 relative to uric acid under different operating conditions.
Intermediate Monitoring: Totalized chromatographic areas of reaction intermediates were monitored, confirming that BDD electrolysis leads to mineralization rather than the formation of stable organic byproducts.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the high-specification Boron Doped Diamond materials required to replicate, scale, and optimize this critical wastewater treatment technology. Our MPCVD BDD products offer the purity, control, and scalability necessary for industrial electrochemical applications.

Applicable Materials

To achieve the high current efficiencies and selective oxidation demonstrated in this research, a highly crystalline, heavy-doped BDD material is essential.

Research Requirement	6CCVD Solution	Material Specification
High Performance Anode	Heavy Boron Doped Diamond (BDD)	MPCVD BDD wafers/plates with controlled doping levels (e.g., 500 mg·dm^-3 equivalent or higher) for maximum hydroxyl radical generation and direct oxidation capacity.
High Purity Surface	Electrochemical Grade PCD	Polycrystalline Diamond (PCD) substrates with guaranteed low non-diamond carbon content (high sp³/sp² ratio) to ensure long electrode lifetime and stability under harsh, high-current density operation.
Substrate Flexibility	Custom Substrates	BDD films grown on various substrates (e.g., Si, Nb, Ti) tailored for specific reactor designs (e.g., Diacell® or filter-press configurations).

Customization Potential

The research utilized a specific electrode area (78.54 cm²) and a thin film (2.83 µm). 6CCVD excels at providing custom dimensions and precise thickness control, enabling seamless transition from R&D to pilot scale.

Large Area Scaling: 6CCVD offers PCD plates/wafers up to 125mm in diameter, significantly exceeding the size used in the study, facilitating industrial scale-up of electrochemical reactors for hospital wastewater treatment.
Thickness Control: We provide precise control over BDD film thickness, ranging from 0.1 µm to 500 µm (SCD/PCD), allowing engineers to optimize material usage and conductivity for specific current density requirements.
Custom Metalization: While the paper focused on the BDD surface, many reactor designs require robust electrical contacts. 6CCVD offers in-house metalization services (Au, Pt, Pd, Ti, W, Cu) to ensure reliable integration into flow cells.
Surface Finish: For applications requiring minimal fouling or specific hydrodynamic properties, 6CCVD provides advanced polishing services, achieving roughness Ra < 5 nm on inch-size PCD plates.

Engineering Support

The key finding of this research is the ability to achieve selective oxidation by controlling current density and flowrate. This optimization relies heavily on the precise characteristics of the BDD material.

6CCVD’s in-house PhD team specializes in material science and electrochemical engineering. We offer consultation services to assist researchers and engineers in:

Optimizing Doping Levels: Tailoring boron concentration to maximize the generation of specific oxidants (e.g., hydroxyl radicals or persulfates) while maintaining high conductivity.
Reactor Design Integration: Providing material selection and dimensioning support for Selective Oxidation projects targeting EDCs and other hazardous species in complex matrices like hospital wastewater.
Quality Assurance: Supplying detailed material characterization data, including sp³/sp² ratios, to guarantee the high quality and reproducibility required for long-term industrial operation.

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

View Original Abstract

This work focuses on the evaluation of the degradation of 17β-estradiol in a mixture of synthetic urine and methanol, trying to determine in which conditions the hormone can be more easily degraded than the urine compounds. This is in the frame of an overall study in which the pre-concentration stage with adsorption/desorption technology is evaluated to improve electrolysis efficiency. Results show that this pollutant can be efficiently removed from mixtures of urine/methanol by electrolysis with diamond electrodes. This removal is simultaneous with the removal of uric acid (used as a model of natural pollutants of urine) and leads to the formation of other organic species that behave as intermediates. This opens the possibility of using a concentration strategy based on the adsorption of pollutants using granular activated carbon and their later desorption in methanol. Despite methanol being a hydroxyl radical scavenger, the electrolysis is found to be very efficient and, in the best case, current charges lower than 7 kAh·m−3 were enough to completely deplete the hormone from urine. Increases in the operation current density lead to faster but less efficient removal of the 17β-estradiol, while increases in the operation flowrate do not markedly affect the efficiency in the removal. Degradation of 17β-estradiol is favored with respect to that of uric acid at low current densities and at high flowrates. In those conditions, direct oxidation processes on the surface of the anode are encouraged. This means that these direct processes can have a higher influence on the degradability of the hazardous species and opens the possibility for the development of selective oxidation processes, with a great economic impact on the degradation of the hazardousness of hospitalary wastewater.

Tech Support

Original Source

DOI: https://doi.org/10.3390/pr8060710

References

2018 - TiO2@C Nanostructured Electrodes for the Anodic Removal of Cocaine [Crossref]
2005 - Degradation of estradiol and ethinyl estradiol by activated sludge and by a defined mixed culture [Crossref]
2010 - Removal of estrone, 17α-ethinylestradiol, and 17ß-estradiol in algae and duckweed-based wastewater treatment systems [Crossref]
2016 - Partial degradation of levofloxacin for biodegradability improvement by electro-Fenton process using an activated carbon fiber felt cathode [Crossref]
2012 - Compuestos emergentes: Implementación de métodos analíticos para extraer y cuantificar 17b-estradiol, 17a-etinilestradiol, ibuprofeno y naproxeno en agua
2009 - A review of the effects of emerging contaminants in wastewater and options for their removal [Crossref]
2012 - Removal of 17 β-Estradiol by Electro-Fenton Process
2014 - Parameters on 17β-Estradiol degradation by Ultrasound in an aqueous system [Crossref]
2016 - Electrochemical degradation of estrone using a boron-doped diamond anode in a filter-press reactor [Crossref]
2013 - Degradation of 17β-estradiol in aqueous solution by ozonation in the presence of manganese(II) and oxalic acid [Crossref]