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6CCVD Research

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

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2025-07-28
JournalMolecules
AuthorsWiyao Maturin Awesso, Ibrahim Tchakala, Sophie Tingry, Geoffroy Lesage, Julie Mendret
InstitutionsInstitut Européen des Membranes, University of Kara
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

The study validates the use of Magnéli phase Ti4O7 anodes for the efficient electro-oxidation (EO) and mineralization of glyphosate, particularly when treating concentrated effluents from Nanofiltration (NF).

  • Optimal Performance: Complete glyphosate degradation (100%) and high mineralization (77.8%) were achieved under optimized acidic conditions (pH 3) and high current density (14 mA cm-2) after 8 hours.
  • NF-EO Synergy: The process successfully treated NF retentate (0.41 mM glyphosate), demonstrating that coupling NF (NF-270 membrane, VCF 4.3) with EO is a viable strategy for reducing treatment volume and managing refractory pollutants.
  • Cost-Effective Alternative: Ti4O7 exhibited performance comparable to the industry standard Boron-Doped Diamond (BDD) electrode, achieving 81.3% mineralization (vs. 90.5% for BDD) in the complex retentate matrix.
  • Energy Efficiency: Specific energy consumption for Ti4O7 (6.09 kWh g-1 TOC) was closely matched to BDD (5.48 kWh g-1 TOC), confirming Ti4O7’s potential as an economically advantageous material.
  • Detoxification Confirmed: Toxicity tests showed a significant reduction in environmental risk; Vibrio fischeri inhibition dropped from a peak of 83.7% (caused by toxic AMPA intermediates) to a final value of 2% after treatment.
  • Mechanism Insight: Degradation proceeds via cleavage of C-N and C-P bonds, generating intermediates like AMPA and glycine, which are subsequently oxidized to carboxylic acids (oxalic, acetic, oxamic) and final inorganic products (CO2, NO3-, PO43-).

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Anode MaterialTi4O7 (Magnéli Phase)N/ASub-stoichiometric titanium oxide
Anode Surface Area32cm22 x 4 cm x 4 cm plate
Cathode MaterialCarbon FeltN/A19 cm x 8 cm x 0.8 cm
Optimal pH (1 mM Glyphosate)3N/AMaximizes ‱OH generation
Optimal Current Density (1 mM Glyphosate)14mA cm-2Achieved 100% degradation
Mineralization (Ti4O7, 1 mM)77.8%At 14 mA cm-2 after 8 h
Mineralization (Ti4O7, NF Retentate)81.3%At 10 mA cm-2 after 8 h
Mineralization (BDD, NF Retentate)90.5%At 10 mA cm-2 after 8 h
Specific Energy (Ti4O7)6.09kWh g-1 TOCTreatment of NF retentate
Specific Energy (BDD)5.48kWh g-1 TOCTreatment of NF retentate
Cell Voltage (Ti4O7, 10 mA cm-2)7.8VDuring 1 mM solution electrolysis
Cell Voltage (BDD, 10 mA cm-2)7.9VDuring NF retentate electrolysis
NF Membrane TypeNF-270 (Polyamide)N/ANominal cutoff 200 Da
NF Conversion Rate (Y)80%Volume Concentration Factor (VCF) of 4.3
Peak Toxicity (AMPA)83.7% InhibitionV. fischeri test, 3 h electrolysis
Final Toxicity (Treated)2% InhibitionV. fischeri test, 8 h electrolysis

Key Methodologies

Section titled “Key Methodologies”
  1. Ti4O7 Anode Fabrication: Sub-stoichiometric titanium oxide (Ti4O7) thin film (50-500 ”m thick) was deposited onto a Ti substrate using plasma deposition of TiOx powder.
  2. Electrochemical Reactor Setup: Experiments were conducted in a 400 mL semi-open cell using the 32 cm2 Ti4O7 anode and a carbon felt cathode, supplied by a constant DC current source.
  3. NF Pre-concentration: A synthetic ionic solution (0.1 mM glyphosate) was concentrated using a DOW Filmtec NF-270 polyamide membrane at 10 bar Transmembrane Pressure (TMP). The process achieved an 80% conversion rate (VCF 4.3), yielding a retentate concentration of 0.41 mM glyphosate.
  4. EO Parameter Optimization: Initial studies focused on optimizing pH (ranging from 2 to 10) and current density (4 to 14 mA cm-2) using a 1 mM glyphosate solution with 50 mM Na2SO4 supporting electrolyte.
  5. Comparative Treatment: The NF retentate was treated by EO using both the Ti4O7 anode and a commercial BDD electrode (2 x 4 cm x 4 cm) at a fixed current density of 10 mA cm-2 for 8 hours.
  6. Glyphosate and By-product Analysis: Concentrations of glyphosate, AMPA, and glycine were monitored using High-Performance Liquid Chromatography coupled with High-Resolution Mass Spectrometry (HPLC-MS/MS) in MRM mode.
  7. Mineralization and Ion Analysis: Total Organic Carbon (TOC) analysis tracked mineralization efficiency. Inorganic ions (phosphate, nitrate, ammonium) and short-chain carboxylic acids (oxalic, acetic, oxamic, formic) were quantified using Ion Exclusion Chromatography.
  8. Toxicity Assessment: Acute toxicity was evaluated using the Microtox screening test (ISO 11348-3), measuring the luminescence inhibition of Vibrio fischeri bacteria after 5 and 15 minutes of exposure.

Commercial Applications

Section titled “Commercial Applications”
  • Industrial Wastewater Treatment: Treating refractory organic pollutants, particularly herbicides and pesticides, in effluents from chemical manufacturing or agricultural processing plants.
  • Membrane Concentrate Management: Integration with Reverse Osmosis (RO) and Nanofiltration (NF) systems to detoxify and mineralize the concentrated brine/retentate, reducing hazardous waste disposal costs.
  • Decentralized Water Purification: Deployment in small-scale or remote systems for treating contaminated groundwater or surface water, leveraging the cost-effectiveness and stability of Ti4O7 over BDD.
  • Advanced Oxidation Processes (AOP) Reactors: Manufacturing and supply of high-performance, structurally stable Ti4O7 electrodes for electrochemical AOPs, including electro-oxidation and potential future electro-Fenton applications.
  • Water Reuse and Reclamation: Achieving high levels of pollutant removal and detoxification necessary to meet stringent regulatory standards for the reuse of agricultural or municipal wastewater.
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

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 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]
  2. 2021 - Classification of the glyphosate target enzyme (5-enolpyruvylshikimate-3-phosphate synthase) for assessing sensitivity of organisms to the herbicide [Crossref]
  3. 2016 - Trends in glyphosate herbicide use in the United States and globally [Crossref]
  4. 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]
  5. 2014 - Impact of glyphosate and glyphosate-based herbicides on the freshwater environment [Crossref]
  6. 2023 - Glyphosate-based herbicide: Impacts, detection, and removal strategies in environmental samples [Crossref]
  7. 2024 - Systemic analysis of glyphosate impact on environment and human health [Crossref]
  8. 2001 - Behavior of glyphosate and aminomethylphosphonic acid (AMPA) in soils and water of reservoir Radeburg II catchment (Saxony/Germany) [Crossref]
  9. 2012 - Forty years with glyphosate

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