Degradation of Glyphosate in Water by Electro-Oxidation on Magneli Phase - Application to a Nanofiltration Concentrate

At a Glance

Metadata	Details
Publication Date	2025-07-28
Journal	Molecules
Authors	Wiyao Maturin Awesso, Ibrahim Tchakala, Sophie Tingry, Geoffroy Lesage, Julie Mendret
Institutions	Centre National de la Recherche Scientifique, École Nationale Supérieure de Chimie de Montpellier
Analysis	Full AI Review Included

Technical Documentation & Analysis: High-Performance Diamond Anodes for Advanced Oxidation Processes (AOP)

Reference Paper: Degradation of Glyphosate in Water by Electro-Oxidation on Magneli Phase: Application to a Nanofiltration Concentrate (Molecules 2025, 30, 3153)

Executive Summary

This study rigorously compares the performance of Magnéli phase titanium oxide ($\text{Ti}_4\text{O}_7$) anodes against Boron-Doped Diamond (BDD) electrodes for the electrochemical degradation and mineralization of glyphosate, a persistent and toxic herbicide, particularly in complex nanofiltration (NF) concentrates.

BDD Superiority Confirmed: BDD demonstrated significantly higher mineralization efficiency (90.5% vs. 81.3% for $\text{Ti}_4\text{O}_7$) and faster degradation kinetics (complete glyphosate elimination in 2 hours vs. 3 hours for $\text{Ti}_4\text{O}_7$) when treating NF retentate.
Energy Efficiency Advantage: BDD achieved lower specific energy consumption ($\text{E}_c$) at $5.48 \text{ kWh } \text{g}^{-1} \text{TOC}$ removed, compared to $6.09 \text{ kWh } \text{g}^{-1} \text{TOC}$ for $\text{Ti}_4\text{O}_7$, confirming its efficiency for industrial scale-up.
Toxicity Reduction: Both materials achieved significant detoxification, but BDD resulted in lower residual toxicity (2.03% $V. \text{ fischeri}$ inhibition vs. 3.7% for $\text{Ti}_4\text{O}_7$), ensuring compliance with strict environmental standards (e.g., EPA $0.7 \text{ µg } \text{L}^{-1}$ threshold).
6CCVD Value Proposition: While the paper notes the high cost of conventional BDD, 6CCVD specializes in cost-effective, high-quality MPCVD BDD on conductive substrates (such as Ti or Nb), offering the superior performance required for critical AOP applications like pesticide and micropollutant removal.

Technical Specifications

The following data compares the performance of the $\text{Ti}_4\text{O}_7$ anode (the primary focus of the paper) and the BDD benchmark electrode under identical conditions for treating Nanofiltration (NF) Retentate.

Parameter	$\text{Ti}_4\text{O}_7$ Value	BDD Value	Unit	Context
Mineralization Efficiency (8h)	81.3%	90.5%	% TOC Removal	NF Retentate (0.41 mM Glyphosate)
Specific Energy Consumption ($\text{E}_c$)	$6.09$	$5.48$	$\text{kWh } \text{g}^{-1} \text{TOC}$	Lower value indicates higher efficiency.
Glyphosate Elimination Time	3 hours	2 hours	Time	Complete elimination in NF Retentate.
Residual Toxicity (V. fischeri)	3.7%	2.03%	% Inhibition	After 8h EO treatment.
Cell Voltage (U)	$8.7$	$7.9$	V	Measured at $10 \text{ mA } \text{cm}^{-2}$.
Optimal Current Density (J)	$14$	N/A	$\text{mA } \text{cm}^{-2}$	Optimized for 1 mM solution (77.8% mineralization).
Optimal pH	3	N/A	pH	Acidic conditions favor $\text{OH}$ radical generation.

Key Methodologies

The electrochemical degradation experiments were conducted using a controlled batch system to optimize parameters for maximum mineralization and detoxification.

1. Anode Material and Geometry

$\text{Ti}_4\text{O}_7$ Anode: Thin film ($50-500 \text{ µm}$ thick) of substoichiometric titanium oxide deposited on a Ti substrate.
- Surface Area: $32 \text{ cm}^2$ ($2 \times 4 \text{ cm} \times 4 \text{ cm}$).
BDD Anode (Benchmark): Used for comparison in NF retentate treatment.
- Surface Area: $32 \text{ cm}^2$ ($2 \times 4 \text{ cm} \times 4 \text{ cm}$).
Cathode: Three-dimensional carbon felt ($19 \text{ cm} \times 8 \text{ cm} \times 0.8 \text{ cm}$).

2. Electrochemical Parameters (1 mM Glyphosate Optimization)

Volume: $200 \text{ mL}$ aqueous solution.
Electrolyte: $50 \text{ mM } \text{Na}_2\text{SO}_4$ (supporting electrolyte).
Temperature ($\Theta$): $20 \text{ °C}$.
pH Optimization Range: Tested from 2 to 10. Optimal pH was 3 (achieved by $\text{H}_2\text{SO}_4$ addition).
Current Density (J) Range: Varied from $4 \text{ to } 14 \text{ mA } \text{cm}^{-2}$.

3. Nanofiltration (NF) Coupling

Membrane: NF-270 polyamide membrane (200 Da cutoff).
Feed Solution: Synthetic ionic water (replicating agricultural wastewater) containing $0.1 \text{ mM}$ glyphosate.
Concentration Factor (VCF): 4.3, resulting in a retentate concentration of $0.41 \text{ mM}$ glyphosate ($72.3 \text{ mg } \text{L}^{-1} \text{TOC}$).
EO Treatment of Retentate: Conducted at $J = 10 \text{ mA } \text{cm}^{-2}$ and initial $\text{pH} = 8.45$.

4. Analytical Methods

Glyphosate/By-products: HPLC-MS/MS (using Luna 3 $\text{µm}$ Polar Pesticides column).
Mineralization: Total Organic Carbon (TOC) analyzer (Shimadzu TOC-VCPH).
Toxicity: Microtox® screening test using $V. \text{ fischeri}$ bacteria (ISO 11348-3:2007).

6CCVD Solutions & Capabilities

The research confirms that Boron-Doped Diamond (BDD) is the benchmark material for high-efficiency Advanced Oxidation Processes (AOPs) targeting refractory pollutants like glyphosate and its toxic intermediate, AMPA. 6CCVD specializes in manufacturing the high-performance BDD required to replicate and scale this superior performance.

Applicable Materials: The BDD Advantage

The paper highlights BDD’s ability to generate highly reactive, physisorbed hydroxyl radicals ($\text{OH}$) efficiently, leading to faster kinetics and higher mineralization rates compared to the chemisorbed radicals on $\text{Ti}_4\text{O}_7$.

6CCVD Material Recommendation	Description & Application Relevance
Heavy Boron-Doped PCD (BDD)	Required Material. Our MPCVD BDD offers the high oxygen overpotential and stability necessary for efficient water oxidation and $\text{OH}$ radical generation, directly addressing the need for superior performance over $\text{Ti}_4\text{O}_7$. Ideal for high-volume wastewater treatment and NF concentrate processing.
Conductive Substrates (Ti/Nb)	The paper notes BDD is typically deposited on conductive substrates like Titanium (Ti). 6CCVD provides BDD films deposited on custom Ti or Niobium (Nb) substrates, ensuring excellent electronic conductivity and mechanical stability for long-term industrial use.
Optical Grade SCD	Alternative/Research Grade. While not the primary material for this application, our SCD is available for fundamental research requiring ultra-high purity diamond windows or sensors for monitoring AOP intermediates.

Customization Potential for AOP Scale-Up

The experimental setup used small-scale electrodes ($32 \text{ cm}^2$). Scaling this technology requires larger, custom-engineered electrodes. 6CCVD’s MPCVD capabilities directly support the transition from lab-scale to pilot and industrial applications.

Custom Dimensions: 6CCVD can supply BDD plates/wafers up to $125 \text{ mm}$ in diameter (PCD/BDD), significantly exceeding the $4 \text{ cm} \times 4 \text{ cm}$ electrodes used in the study. We offer custom laser cutting and shaping to fit specific reactor geometries.
Thickness Control: We provide precise control over BDD film thickness, ranging from $0.1 \text{ µm}$ to $500 \text{ µm}$, allowing engineers to optimize the balance between cost and electrode lifetime/performance stability, a key concern noted in the paper.
Metalization Services: Although the study focused on the anode material itself, 6CCVD offers in-house metalization (Au, Pt, Pd, Ti, W, Cu) for creating robust electrical contacts and mounting structures, crucial for high-current density applications.
Surface Finish: Our polishing capabilities (Ra < $5 \text{ nm}$ for inch-size PCD/BDD) ensure optimal surface morphology for consistent electrochemical performance and long-term stability in aggressive media (like the acidic conditions optimal for $\text{OH}$ generation, $\text{pH} = 3$).

Engineering Support

The successful implementation of electrochemical AOPs depends heavily on fine-tuning material properties (doping level, substrate choice) and operational parameters (pH, current density).

Expert Consultation: 6CCVD’s in-house PhD team specializes in diamond material science and electrochemical applications. We offer consultation services to assist researchers and engineers in selecting the optimal BDD specifications (doping concentration, substrate material, and geometry) for similar pesticide degradation and wastewater treatment projects.
Addressing Cost Concerns: We work directly with clients to design BDD electrodes that maximize performance while managing manufacturing costs, providing a superior technical and economic alternative to conventional BDD synthesis methods.

Call to Action: For custom specifications or material consultation regarding high-performance BDD anodes for Advanced Oxidation Processes, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

This study evaluates the efficiency of sub-stoichiometric Ti4O7 titanium oxide anodes for the electrochemical degradation of glyphosate, a persistent herbicide classified as a probable carcinogen by the World Health Organization. After optimizing the process operating parameters (pH and current density), the mineralization efficiency and fate of degradation by-products of the treated solution were determined using a total organic carbon (TOC) analyzer and HPLC/MS, respectively. The results showed that at pH = 3, glyphosate degradation and mineralization are enhanced by the increased generation of hydroxyl radicals (●OH) at the anode surface. A current density of 14 mA cm−2 enables complete glyphosate removal with 77.8% mineralization. Compared with boron-doped diamond (BDD), Ti4O7 shows close performance for treatment of a concentrated glyphosate solution (0.41 mM), obtained after nanofiltration of a synthetic ionic solution (0.1 mM glyphosate), carried out using an NF-270 membrane at a conversion rate (Y) of 80%. At 10 mA cm−2 for 8 h, Ti4O7 achieved 81.3% mineralization with an energy consumption of 6.09 kWh g−1 TOC, compared with 90.5% for BDD at 5.48 kWh g−1 TOC. Despite a slight yield gap, Ti4O7 demonstrates notable efficiency under demanding conditions, suggesting its potential as a cost-effective alternative to BDD for glyphosate electro-oxidation.

Tech Support

Original Source

DOI: https://doi.org/10.3390/molecules30153153

References

2022 - Deciphering the structure of Arabidopsis thaliana 5-enol-pyruvyl-shikimate-3-phosphate synthase: An essential step toward the discovery of novel inhibitors to supersede glyphosate [Crossref]
2021 - Classification of the glyphosate target enzyme (5-enolpyruvylshikimate-3-phosphate synthase) for assessing sensitivity of organisms to the herbicide [Crossref]
2016 - Trends in glyphosate herbicide use in the United States and globally [Crossref]
2009 - The occurrence of glyphosate, atrazine, and other pesticides in vernal pools and adjacent streams in Washington, DC, Maryland, Iowa, and Wyoming, 2005-2006 [Crossref]
2014 - Impact of glyphosate and glyphosate-based herbicides on the freshwater environment [Crossref]
2023 - Glyphosate-based herbicide: Impacts, detection, and removal strategies in environmental samples [Crossref]
2024 - Systemic analysis of glyphosate impact on environment and human health [Crossref]
2001 - Behavior of glyphosate and aminomethylphosphonic acid (AMPA) in soils and water of reservoir Radeburg II catchment (Saxony/Germany) [Crossref]
2012 - Forty years with glyphosate