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6CCVD Research

Degradation of methylparaben by anodic oxidation, electro-Fenton, and photoelectro-Fenton using carbon felt-BDD cell

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2025-05-01
JournalSeparation and Purification Technology
AuthorsAline B. Trench, Nihal Oturan, Aydeniz Demir, JoĂŁo P.C. Moura, ClĂŠment Trellu
Citations3
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

This research investigates the comparative efficiency of three Electrochemical Advanced Oxidation Processes (EAOPs)—Anodic Oxidation (AO-H2O2), Electro-Fenton (EF), and Photoelectro-Fenton (PEF)—for the degradation and mineralization of methylparaben (MP) using a Boron-Doped Diamond (BDD) anode and a cost-effective Carbon Felt (CF) cathode.

  • Efficiency Ranking: The mineralization efficiency of MP consistently followed the sequence: AO-H2O2 < EF < PEF across all tested current densities, confirming the synergistic benefits of Fenton chemistry and UV irradiation.
  • PEF Superiority: The PEF process demonstrated exceptional performance, achieving 84.65% Total Organic Carbon (TOC) removal in only 2 hours at a low current density of 5 mA cm-2.
  • EF Performance: EF achieved a maximum TOC removal of 91.86% after 6 hours at 10 mA cm-2, significantly outperforming AO-H2O2 (74.98% TOC removal) under the same conditions.
  • Cost-Effectiveness: EF was identified as the most cost-effective option compared to AO-H2O2, exhibiting higher mineralization current efficiency (MCE) and lower energy consumption (EC).
  • Kinetics and Mechanism: MP degradation followed pseudo-first-order kinetics. The absolute rate constant (kMP) for the reaction between MP and hydroxyl radicals was determined to be 8.0 x 108 M-1 s-1. A detailed mineralization pathway involving aromatic intermediates (e.g., hydroquinone, benzoquinone) and short-chain carboxylic acids (e.g., oxalic acid) was proposed.
  • Material Advantage: The use of the unmodified CF cathode is highlighted as a low-cost alternative to complex gas diffusion electrodes, simplifying the EAOP setup while maintaining high efficiency.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Anode MaterialBoron-Doped Diamond (BDD)N/AOn Niobium support
Cathode MaterialUnmodified Carbon Felt (CF)N/ALow-cost, high surface area
Electrode Surface Area4cm22 x 2 cm2 for both electrodes
Electrolyte Volume100mLTotal solution volume
Initial MP Concentration0.1mMPollutant concentration
Supporting Electrolyte50mMNa2SO4
Optimal pH (EF/PEF)3N/ARequired for Fe2+ catalyst stability
Fe2+ Catalyst Concentration0.1mMAdded as FeSO4
Current Density Range Tested2.5 to 17.5mA cm-2Applied constant current
PEF Light Source200 WN/AMedium-pressure mercury arc lamp
Highest TOC Removal (PEF)96.8%After 6 h at 5 mA cm-2
Highest TOC Removal (EF)91.86%After 6 h at 10 mA cm-2
Highest kapp (PEF)0.271min-1At 5 mA cm-2
Absolute Rate Constant (kMP)8.0 x 108M-1 s-1MP/•OH reaction rate constant
Lowest Energy Consumption (EF)0.32kWh (gTOC)-1At 2.5 mA cm-2 (6 h treatment)
Theoretical Electrons (n)34N/AFor MP mineralization (C8H8O3)

Key Methodologies

Section titled “Key Methodologies”

The comparative study utilized a 200 mL undivided cylindrical glass cell under constant-current electrolysis conditions.

  1. Electrolyte Preparation: 100 mL of aqueous solution containing 0.1 mM methylparaben (MP) and 50 mM sodium sulfate (Na2SO4) was prepared.
  2. Oxygen Saturation: Pressurized air was bubbled into the solution for 5 minutes before starting the experiment to ensure saturated dissolved oxygen, which is necessary for in situ H2O2 generation at the cathode.
  3. Electrode Configuration: A Boron-Doped Diamond (BDD) film anode and an unmodified Carbon Felt (CF) cathode were used, each having a surface area of 4 cm2.
  4. EF/PEF Specifics: For Electro-Fenton (EF) and Photoelectro-Fenton (PEF) processes, the solution pH was adjusted to 3.0, and 0.1 mM FeSO4 was added as the catalyst source.
  5. PEF Operation: The PEF process involved continuous UV irradiation using a 200 W medium-pressure mercury arc lamp (spectral range 254-579 nm). The electrolyte temperature was maintained at 20 °C.
  6. MP and Intermediate Analysis: MP concentration decay and the evolution of aromatic byproducts were monitored using High-Performance Liquid Chromatography (HPLC) with UV detection at 254 nm.
  7. Mineralization Assessment: Total Organic Carbon (TOC) removal was measured using a Shimadzu TOC-VCSH analyzer based on thermal catalytic oxidation at 680 °C.
  8. Carboxylic Acid Analysis: Short-chain carboxylic acids (e.g., oxalic, malic, formic) were quantified using liquid chromatography with a Rezex column and UV detection at 220 nm.

Commercial Applications

Section titled “Commercial Applications”

The demonstrated high efficiency and low energy consumption of the PEF process using BDD/CF electrodes make this technology highly relevant for advanced water treatment applications, particularly for persistent organic pollutants.

  • Wastewater Treatment (WWT): Implementation as a tertiary treatment step for municipal and industrial effluents to meet stringent discharge limits for recalcitrant compounds.
  • Removal of Endocrine Disrupting Chemicals (EDCs): Specific application for eliminating parabens (like MP) and other pharmaceuticals/personal care products (PPCPs) from water sources.
  • Water Reuse and Potable Water Production: Use in advanced purification trains where complete mineralization (high TOC removal) is required for water recycling.
  • Electrochemical Reactor Design: Development of modular, energy-efficient EAOP reactors utilizing the superior performance of BDD anodes coupled with cost-effective, high-surface-area Carbon Felt cathodes.
  • Catalyst Regeneration Systems: The PEF process’s ability to photochemically regenerate the Fe2+ catalyst (Eq. 16) minimizes catalyst consumption and sludge generation, improving operational sustainability.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 1999 - Polar drug residues in sewage and natural waters in the state of Rio de Janeiro, Brazil [Crossref]
  2. 2014 - Parabens. From environmental studies to human health [Crossref]
  3. 2015 - Occurrence, fate and behavior of parabens in aquatic environments: a review [Crossref]
  4. 2016 - Ecological risk assessment associated to the removal of endocrine-disrupting parabens and benzophenone-4 in wastewater treatment [Crossref]
  5. 2014 - Occurrence and ecological potential of pharmaceuticals and personal care products in groundwater and reservoirs in the vicinity of municipal landfills in China [Crossref]
  6. 2008 - The occurrence of pharmaceuticals, personal care products, endocrine disruptors and illicit drugs in surface water in South Wales, UK [Crossref]
  7. 2014 - Occurrence of acidic pharmaceuticals and personal care products in Turia River Basin: from waste to drinking water [Crossref]
  8. 2022 - Occurrence and human exposure assessment of parabens in water sources in Osun State Nigeria [Crossref]
  9. 2016 - Occurrence and risk assessment of parabens and triclosan in surface waters of southern Brazil: a problem of emerging compounds in an emerging country [Crossref]
  10. 2016 - The occurrence of methyl, ethyl, propyl, and butyl parabens in the urban rivers and stormwaters of Sydney, Australia [Crossref]

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