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6CCVD Research

Electrochemical Oxidation of Selected Micropollutants from Environment Matrices Using Boron-Doped Diamond Electrodes - Process Efficiency and Transformation Product Detection

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2024-12-11
JournalWater
AuthorsFilip GamoƄ, S. Ć»abczyƄski, MaƂgorzata SzopiƄska, Mattia Pierpaoli, Dawid Zych
InstitutionsSilesian University of Technology, University of Opole
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

This study validates the high efficiency of Electrochemical Oxidation (EO) using Boron-Doped Diamond (BDD) anodes for removing persistent micropollutants (MPs) from complex environmental matrices.

  • Exceptional MP Removal: The EO-BDD process achieved outstanding removal efficiencies for Bisphenol A (BPA) and Diclofenac (DCF), exceeding 99% in Landfill Leachate (LL) and 96% in the less organically loaded Treated Wastewater (TWW-D).
  • Matrix Complexity Handling: BDD anodes successfully treated highly challenging LL, achieving 94.24% Chemical Oxygen Demand (COD) removal and 78.25% Ammonium Nitrogen (N-NH4+) removal, demonstrating strong mineralization capability.
  • Material Advantage: BDD’s wide oxygen overpotential window and resistance to fouling facilitate the stable generation of powerful oxidants (hydroxyl radicals, reactive chlorine species), crucial for indirect EO in complex, high-salinity matrices like LL.
  • Doping Level Insensitivity: Variations in boron doping (0.5k ppm vs. 10k ppm) showed minimal impact on removal efficiency for COD, N-NH4+, BPA, and DCF, confirming that current density is the primary operational control parameter.
  • Degradation Pathway Insight: Analysis identified four transformation products (TPs) for both BPA and DCF, confirming degradation mechanisms involving hydroxylation and cleavage, supporting the use of EO-BDD as a reliable advanced oxidation process (AOP).
  • Regulatory Compliance: The results strongly support the applicability of EO-BDD as a quaternary treatment stage to help wastewater treatment plants comply with new European Union directives mandating effective MP removal.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
BDD Substrate MaterialNiobium (Nb)-50 mm diameter
BDD Growth MethodMWPECVD-Microwave Plasma-Enhanced Chemical Vapour Deposition
Substrate Temperature700°CDuring BDD deposition
Microwave Power1300WDuring BDD deposition
Total Pressure50TorrDuring BDD deposition
Boron Doping Level (Low)~1.5 x 1017at/cm3Referred to as 0.5k ppm
Boron Doping Level (High)3 x 1021at/cm3Referred to as 10k ppm
Anode Geometric Area10.5cm2BDD electrode surface area
Anode-Cathode Distance~2.5cmElectrolytic cell setup
Current Density (LL)120mA/cm2Landfill Leachate treatment
Current Density (TWW)25mA/cm2Treated Wastewater treatment
Maximum BPA Removal (LL, 4h)>99.85%0.5k BDD anode
Maximum DCF Removal (LL, 4h)>99.23%0.5k BDD anode
Maximum COD Removal (LL, 8h)94.24%10k BDD anode
Maximum N-NH4+ Removal (LL, 8h)78.25%10k BDD anode
LOQ (BPA)0.40”g/LLimit of Quantification
LOQ (DCF)0.08”g/LLimit of Quantification

Key Methodologies

Section titled “Key Methodologies”
  1. BDD Anode Preparation: Boron-doped diamond films were grown on 50-mm Niobium substrates using Microwave Plasma-Enhanced Chemical Vapour Deposition (MWPECVD).
  2. Substrate Pre-treatment: Niobium substrates were sandblasted, cleaned ultrasonically in acetone and isopropanol, and seeded with a water-based diamond slurry.
  3. Deposition Recipe: BDD growth occurred at 700 °C, 1300 W microwave power, and 50 Torr pressure, utilizing H2, CH4, and B2H6 gas mixtures to achieve two distinct boron doping levels (0.5k ppm and 10k ppm).
  4. Electrochemical Setup: A custom 400-mL undivided electrolytic cell was used, featuring the BDD electrode (10.5 cm2) as the anode and a stainless-steel mesh as the cathode, separated by approximately 2.5 cm.
  5. Operational Conditions: All EO tests were performed under galvanostatic control. Current densities were optimized based on matrix type: 120 mA/cm2 for Landfill Leachate (LL) and 25 mA/cm2 for Treated Wastewater (TWW).
  6. Sample Matrices: Experiments utilized real-world samples: Landfill Leachate (LL), and two types of Treated Wastewater (TWW-W and TWW-D), spiked with BPA and DCF.
  7. Micropollutant Quantification: Concentrations were determined using Ultra-High-Performance Liquid Chromatography coupled with tandem Mass Spectrometry (UHPLC-MS/MS) following Solid-Phase Extraction (SPE).
  8. Transformation Product (TP) Analysis: TPs were identified by spiking BPA and DCF into a phosphate buffer (PB) matrix and analyzing samples via UHPLC-MS/MS in Single Ion Monitoring (SIM) mode (negative ionization) to isolate direct EO degradation mechanisms.

Commercial Applications

Section titled “Commercial Applications”
  • Quaternary Wastewater Treatment (Q-WWT): Deployment of BDD-based EO systems as a final polishing step in municipal WWTPs to ensure compliance with strict regulatory limits for persistent micropollutants (e.g., DCF, BPA).
  • Landfill Leachate Treatment: High-efficiency EO systems capable of handling the high organic load (COD) and high salinity (Cl- concentration up to 2690 mg/L) characteristic of LL, enabling effective mineralization and nitrogen removal.
  • Industrial Effluent Detoxification: Remediation of concentrated industrial waste streams, particularly those containing endocrine-disrupting chemicals (EDCs) like BPA, originating from plastics, paper, or chemical manufacturing.
  • Pharmaceutical Waste Destruction: Targeted electrochemical destruction of active pharmaceutical ingredients (APIs) in concentrated hospital or manufacturing waste, preventing their release into the environment.
  • Water Reuse and Recycling: Integration into advanced water purification trains to eliminate trace organic contaminants, making treated water suitable for industrial cooling, irrigation, or aquifer recharge.
  • Advanced Electrode Manufacturing: Supply of highly stable, customized BDD electrodes (0.5k ppm and 10k ppm doping) for commercial Advanced Oxidation Processes (AOPs) requiring high current efficiency and resistance to fouling.
View Original Abstract

Bisphenol A (BPA) and diclofenac (DCF) are among the most prevalent micropollutants in aquatic environments, with concentrations reaching up to several hundred ”g/L. These compounds pose significant risks to biodiversity and environmental health, necessitating the development of effective removal methods. However, both BPA and DCF can be resistant to conventional treatment technologies, highlighting the need for innovative approaches. Electrochemical oxidation (EO) has emerged as a promising solution. In this study, we assessed the effectiveness of EO using boron-doped diamond (BDD) anodes to remove BPA and DCF from two types of treated wastewater (TWW-W and TWW-D) and landfill leachate (LL). The evaluation included an analysis of the removal efficiency of BPA and DCF and the identification of transformation products generated during the process. Additionally, the feasibility of the EO-BDD process to remove ammonium nitrogen (N-NH4+) and organic compounds present in these environmental matrices was investigated. The EO-BDD treatment achieved remarkable removal efficiencies, reducing BPA and DCF concentrations by over 96% in LL and TWW-W. Transformation product analyses identified four intermediates formed from parent compounds during the oxidation process. Furthermore, the EO-BDD process effectively removed both chemical oxygen demand (COD) and ammonium nitrogen from LL, although weaker results were observed for TWWs. These findings underscore the potential of the EO-BDD process as an effective method for the removal of BPA and DCF from challenging matrices, such as wastewater containing micropollutants. It also shows promise as a complementary technology for enhancing current conventional wastewater treatment methods, especially biological degradation.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2019 - Performance of secondary wastewater treatment methods for the removal of contaminants of emerging concern implicated in crop uptake and antibiotic resistance spread: A review [Crossref]
  2. 2020 - Antimicrobial pharmaceuticals in the aquatic environment—Occurrence and environmental implications [Crossref]
  3. 2021 - Oxidative degradation and mineralisation of the endocrine-disrupting chemical bisphenol A by an eco-friendly system based on UV-solar/H2O2 with reduction of genotoxicity and cytotoxicity levels [Crossref]
  4. 2024 - Bisphenol A in dairy products: Amount, potential risks, and various analytical methods—A systematic review [Crossref]
  5. 2017 - Occurrence and effects of plastic additives on marine environments and organisms: A review [Crossref]
  6. 1998 - Xenoestrogens: The emerging story of bisphenol A [Crossref]
  7. 2019 - Assessment of bisphenol-A in the urban water cycle [Crossref]
  8. 2015 - Exploring potential contributors to endocrine disrupting activities in Taiwan’s surface waters using yeast assays and chemical analysis [Crossref]
  9. 2014 - Fate of diclofenac in municipal wastewater treatment plants—A review [Crossref]

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