Effective Degradation of Metronidazole through Electrochemical Activation of Peroxymonosulfate - Mechanistic Insights and Implications

At a Glance

Metadata	Details
Publication Date	2024-04-05
Journal	Energies
Authors	Haicen Liao, Jingkai Fang, Jiahao Wang, Xianhu Long, Igor Ying Zhang
Institutions	Collaborative Innovation Center of Chemistry for Energy Materials, Sichuan University
Citations	10
Analysis	Full AI Review Included

Technical Documentation & Analysis: High-Efficiency Wastewater Treatment via EC-PMS-BDD

This document analyzes the research paper “Effective Degradation of Metronidazole through Electrochemical Activation of Peroxymonosulfate” (Energies 2024, 17, 1750) to highlight the critical role of Boron-Doped Diamond (BDD) anodes and connect the findings directly to 6CCVD’s advanced MPCVD diamond material solutions.

Executive Summary

The research conclusively validates Boron-Doped Diamond (BDD) as the superior anode material for electrochemical advanced oxidation processes (EAOPs) utilizing peroxymonosulfate (PMS) activation for contaminant degradation.

Superior Performance: The EC-PMS-BDD system achieved 99.5% Metronidazole (MNZ) degradation, significantly surpassing the 64.3% removal achieved by Dimensionally Stable Anodes (DSA) under identical conditions.
High Efficiency: Optimal operational parameters (Current Density: 13.3 mA/cm², pH: 3.7, PMS Dosage: 2.4 mmol·L^-1) resulted in 100% MNZ removal within 40 minutes.
Mechanistic Advantage: BDD’s high oxygen evolution over-potential facilitates the efficient generation of highly reactive species, including hydroxyl radicals (•OH), sulfate radicals (SO₄•¯), and singlet oxygen (¹O₂), which are crucial for rapid degradation.
Energy Optimization: The EC-PMS-BDD system demonstrated high energy efficiency, achieving an Electric Energy per Order (EE/O) of only 7.6 kWh m^-3 for MNZ removal.
Broad Applicability: The BDD system effectively degraded other persistent organic pollutants (SMX, CBZ, NB), confirming its universal applicability for complex medical wastewater treatment.
Material Requirement: The study underscores the necessity of high-quality, electrochemically active BDD material for replicating and scaling up these high-performance EAOP systems.

Technical Specifications

Parameter	Value	Unit	Context
Anode Material Comparison	BDD > DSA	N/A	BDD showed superior electrochemical activity and degradation efficiency.
BDD MNZ Removal (EC-PMS)	99.5	%	Achieved in 30 min at 33.3 mA/cm² (vs. 64.3% for DSA).
Optimal Current Density	13.3	mA/cm²	Predicted optimal condition for 100% removal.
Optimal Initial pH	3.7	N/A	Predicted optimal condition for 100% removal.
Optimal PMS Dosage	2.4	mmol·L^-1	Predicted optimal condition for 100% removal.
Optimal Reaction Time	40	min	Time required for 100% MNZ removal under optimal conditions.
Electrode Dimensions Used	3 x 3 x 0.1	cm	Physical dimensions of the BDD/DSA anodes tested.
Effective Working Area	9	cm²	Active surface area of the electrodes.
Electric Energy per Order (EE/O)	7.6	kWh m^-3	Energy consumption for MNZ degradation (highly efficient).
Key Reactive Species Detected	•OH, SO₄•¯, ¹O₂	N/A	Confirmed by EPR and chemical probe experiments.

Key Methodologies

The study employed a systematic electrochemical activation process coupled with advanced analytical techniques.

Electrochemical Reactor Setup: Experiments were conducted in a 250 mL glass beaker containing 160 mL of MNZ solution (80 µmol·L^-1). A DC power source maintained constant current density.
Electrode Configuration: BDD or DSA anodes (3 cm x 3 cm x 0.1 cm) were paired with graphite cathodes of the same dimensions, positioned in parallel with a 2 cm gap.
Electrolyte and Reagents: Sodium sulfate (Na₂SO₄) at 20 mmol·L^-1 served as the supporting electrolyte. Peroxymonosulfate (PMS) dosage was varied (1 to 5 mmol·L^-1).
Parameter Optimization: Response Surface Methodology (RSM) using a Box-Behnken Design was utilized to optimize four key parameters: current density (11.1 to 33.3 mA/cm²), initial pH (3 to 9), PMS dosage, and reaction time (25 to 45 min).
Radical Detection: Electron Paramagnetic Resonance (EPR) spectroscopy (using DMPO and TEMP spin traps) and chemical probe experiments (Coumarin, p-HBA, DPA) confirmed the generation and involvement of •OH, SO₄•¯, and ¹O₂ radicals.
Byproduct Analysis: Ultrahigh-Performance Liquid Chromatography-Quadrupole Time-of-Flight Mass Spectrometry (UHPLC-QTOF-MS) identified degradation intermediates, and the Toxicity Estimation Software Tool (T.E.S.T.) evaluated their environmental toxicity.

6CCVD Solutions & Capabilities

The research clearly demonstrates that Boron-Doped Diamond (BDD) is the enabling material for high-performance electrochemical wastewater treatment. 6CCVD is uniquely positioned to supply the high-quality BDD required for both research replication and industrial scale-up of EC-PMS-BDD systems.

Applicable Materials

To replicate and extend this research, the following 6CCVD material is explicitly required:

Heavy Boron-Doped Diamond (BDD): Essential for achieving the high oxygen evolution over-potential necessary for efficient electrochemical activation of PMS and subsequent radical generation (•OH, SO₄•¯, ¹O₂). 6CCVD provides BDD films with optimized doping levels for maximum electrochemical activity in AOPs.

Customization Potential

The study utilized specific 3 cm x 3 cm x 0.1 cm electrodes. 6CCVD’s MPCVD capabilities allow for precise replication and significant scale-up:

Research Requirement	6CCVD Customization Capability	Sales Advantage
Specific Dimensions	Custom Plates/Wafers up to 125mm (PCD)	We can supply BDD electrodes in the exact 9 cm² size used, or scale up to large-area plates (up to 125mm diameter) for pilot and industrial reactors.
Thickness Control	BDD Thickness (0.1 µm - 500 µm)	Precise control over BDD film thickness ensures optimal conductivity and mechanical stability, crucial for long-term operation in corrosive wastewater environments.
Substrate Integration	Substrates up to 10mm	We provide BDD films grown on highly conductive substrates (e.g., Niobium or Tantalum) for robust current distribution and ease of integration into electrochemical cells.
Electrical Contacting	Custom Metalization (Au, Pt, Pd, Ti, W, Cu)	We offer in-house metalization services to apply robust contact layers (e.g., Ti/Pt/Au) directly to the BDD surface, ensuring low-resistance electrical connections necessary for high current density operation.
Surface Finish	Polishing (Ra < 5nm for Inch-size PCD)	Custom polishing services ensure a consistent surface finish, minimizing fouling and maximizing the active electrochemical area for consistent radical production.

Engineering Support

The successful implementation of EC-PMS-BDD systems relies on precise material selection and process optimization.

AOP/EAOP Expertise: 6CCVD’s in-house PhD team specializes in the material science of diamond electrodes for Advanced Oxidation Processes (AOPs) and Electrochemical Activation (EA) projects.
Material Consultation: We assist engineers and scientists in selecting the optimal BDD doping concentration, film thickness, and substrate material to maximize efficiency (e.g., achieving the low EE/O of 7.6 kWh m^-3 observed in this MNZ degradation study).
Global Logistics: We ensure reliable, global shipping (DDU default, DDP available) of sensitive diamond materials, supporting international research and industrial deployment.

Call to Action: For custom specifications or material consultation regarding high-efficiency electrochemical wastewater treatment using BDD, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

The investigation into the degradation of metronidazole (MNZ), a frequently employed antibiotic, through the electrochemical activation of peroxymonosulfate (PMS) utilizing either boron-doped diamond (BDD) or dimensional stable anode (DSA) as the anode, was conducted in a systematic manner. The enhancement of MNZ removal was observed with increasing current density, PMS dosage, and initial pH. Response surface methodology (RSM), based on a Box-Benken design, was utilized to evaluate the efficiency of MNZ elimination concerning current density (ranging from 11.1 to 33.3 mA/cm2), initial pH (ranging from 3 to 9), PMS dosage (ranging from 1 to 5 mmol·L−1), and reaction time (ranging from 25 to 45 min). The optimal operational conditions for MNZ removal were determined as follows: a current density of 13.3 mA/cm2, a pH of 3.7, a PMS dosage of 2.4 mmol·L−1, and a reaction time of 40 min. Electron paramagnetic resonance (EPR), quenching experiments, and chemical probe experiments confirmed the involvement of •OH, SO4•− and 1O2 radicals as the primary reactive species in MNZ degradation. The presence of HCO3− and H2PO4− hindered MNZ removal, whereas the presence of Cl− accelerated it. The degradation pathways of MNZ were elucidated by identifying intermediates and assessing their toxicity. Additionally, the removal efficiencies of other organic pollutants, such as sulfamethoxazole (SMX), carbamazepine (CBZ), and nitrobenzene (NB), were compared. This study contributes to a comprehensive understanding of MNZ degradation efficiency, mechanisms, and pathways through electrochemical activation of PMS employing BDD or DSA anodes, thereby offering valuable insights for the selection of wastewater treatment systems.

Tech Support

Original Source

DOI: https://doi.org/10.3390/en17071750

References

2019 - Synthesis and application of stable, reusable TiO2 polymeric composites for photocatalytic removal of metronidazole: Removal kinetics and density functional analysis [Crossref]
2013 - Impact of pharmaceutical industry treated effluents on the water quality of river Uppanar, South east coast of India: A case study [Crossref]
2004 - Resistance in the environment [Crossref]
2020 - Application of response surface methodology for optimization of electrochemical process in metronidazole (MNZ) removal from aqueous solutions using stainless steel 316 (SS316) and lead (Pb) anodes
2019 - Degradation of metronidazole by UV/chlorine treatment: Efficiency, mechanism, pathways and DBPs formation [Crossref]
2013 - Simultaneous determination of metronidazole, chloramphenicol and 10 sulfonamide residues in honey by LC-MS/MS [Crossref]
2021 - Fabrication of magnetic CuFe2O4@PBC composite and efficient removal of metronidazole by the photo-Fenton process in a wide pH range [Crossref]
2022 - A novel ZnO/biochar composite catalysts for visible light degradation of metronidazole [Crossref]
2020 - Characterisation and bioremediation of wastewater: A review exploring bioremediation as a sustainable technique for pharmaceutical wastewater [Crossref]