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6CCVD Research

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

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2024-04-05
JournalEnergies
AuthorsHaicen Liao, Jingkai Fang, Jiahao Wang, Xianhu Long, Igor Ying Zhang
InstitutionsFudan University, Sichuan University
Citations10
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

This study investigates the highly effective degradation of Metronidazole (MNZ), a persistent antibiotic, using electrochemical activation of peroxymonosulfate (PMS) with Boron-Doped Diamond (BDD) anodes.

  • Superior Performance: The EC-PMS-BDD system achieved 100% MNZ removal under optimized conditions, significantly outperforming the system utilizing Dimensionally Stable Anodes (DSA).
  • Optimization Achieved: Optimal operational parameters were determined using Response Surface Methodology (RSM): Current density of 13.3 mA/cm2, initial pH of 3.7, PMS dosage of 2.4 mmol¡L-1, and a reaction time of 40 min.
  • Mechanism Elucidation: Electron Paramagnetic Resonance (EPR) and quenching experiments confirmed the synergistic involvement of multiple reactive oxygen species (ROS): hydroxyl radicals (•OH), sulfate radicals (SO4•¯), and singlet oxygen (1O2).
  • Anode Material Impact: BDD anodes facilitate higher yields of 1O2 and •OH compared to DSA, contributing to the superior degradation efficiency, attributed to BDD’s high oxygen evolution over-potential.
  • Energy Efficiency: The process demonstrated high energy efficiency for MNZ degradation, achieving an Electric Energy per Order (EE/O) of 7.6 kWh¡m-3.
  • Broad Applicability: The method successfully degraded other persistent organic pollutants (POPs) including sulfamethoxazole (SMX), carbamazepine (CBZ), and nitrobenzene (NB).
  • Toxicity Assessment: Degradation pathways were identified, showing that intermediate byproducts generally exhibited lower bioaccumulation factors and reduced mutagenicity compared to the parent MNZ compound.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Optimal Current Density13.3mA/cm2Optimized condition for 100% MNZ removal
Optimal Initial pH3.7-Optimized condition
Optimal PMS Dosage2.4mmol¡L-1Optimized condition
Optimal Reaction Time40minOptimized condition
MNZ Removal Efficiency (Optimal)100%EC-PMS-BDD system
MNZ EE/O7.6kWh¡m-3Electric Energy per Order (low consumption)
CBZ EE/O20.6kWh¡m-3Electric Energy per Order
Standard Current Density33.3mA/cm2Standard experimental condition
Initial MNZ Concentration80¾mol¡L-1Standard experimental concentration
Supporting Electrolyte (Na2SO4)20mmol¡L-1Standard experimental concentration
Standard PMS Dosage1mmol¡L-1Standard experimental concentration
BDD Anode Dimensions3 x 3 x 0.1cmElectrode size
Effective Working Area9cm2Anode/Cathode working area
EC-BDD MNZ Removal (45 min, no PMS)92.7%Electrolysis only
EC-PMS-BDD MNZ Removal (45 min)99.5%Electrolysis + PMS activation

Key Methodologies

Section titled “Key Methodologies”

The degradation experiments utilized a systematic electrochemical setup coupled with advanced analytical techniques:

  1. Electrochemical Reactor Setup: Experiments were conducted in a 250 mL glass beaker reactor containing 160 mL of solution. Electrodes (3 cm x 3 cm x 0.1 cm) were positioned in parallel, 2 cm apart, with a working area of 9 cm2.
  2. Anode Materials Comparison: Boron-Doped Diamond (BDD) and Dimensionally Stable Anode (DSA) were tested as anodes, with graphite serving as the cathode.
  3. Solution Preparation: Solutions contained 80 ¾mol¡L-1 MNZ, 20 mmol¡L-1 Na2SO4 (supporting electrolyte), and a predetermined PMS dosage (standard 1 mmol¡L-1). pH was adjusted using NaOH and H2SO4.
  4. Process Optimization (RSM-BBD): The Box-Behnken Design (BBD) model within Response Surface Methodology (RSM) was employed to optimize the synergistic effects of four key variables: current density (11.1 to 33.3 mA/cm2), initial pH (3 to 9), PMS dosage (1 to 5 mmol¡L-1), and reaction time (25 to 45 min).
  5. Radical Identification (EPR): Electron Paramagnetic Resonance (EPR) spectroscopy, using DMPO (for •OH and SO4•¯) and TEMP (for 1O2) spin-trapping agents, was used to confirm the generation and relative concentrations of reactive species.
  6. Quenching and Probe Experiments: Radical scavengers (TBA, Ethanol, FFA, L-Histidine) and chemical probes (coumarin for •OH, p-HBA for SO4•¯, DPA for 1O2) were used to quantify the contribution of specific radicals to MNZ degradation.
  7. Byproduct Analysis: Ultrahigh-Performance Liquid Chromatography-Quadrupole Time-of-Flight Mass Spectrometry (UHPLC-QTOF-MS) was used to identify transformation products.
  8. Toxicity Evaluation: Toxicity Estimation Software Tool (T.E.S.T.) using Quantitative Structure-Activity Relationship (QSAR) models assessed acute toxicity, bioaccumulation, developmental toxicity, and mutagenicity of MNZ and its byproducts.

Commercial Applications

Section titled “Commercial Applications”

The findings support the implementation of BDD-based electrochemical systems in high-demand water treatment sectors:

  • Pharmaceutical Wastewater Treatment: Direct application for the effective and rapid removal of persistent antibiotics (MNZ, SMX) and other pharmaceutical contaminants (CBZ) from hospital and manufacturing effluent.
  • Advanced Water Purification: Deployment of BDD anodes in electrochemical advanced oxidation processes (EAOPs) for municipal and industrial water reuse systems requiring high contaminant mineralization rates.
  • Refractory Organic Pollutant Remediation: Use of the EC-PMS-BDD system to treat water contaminated with difficult-to-degrade compounds, leveraging the high oxidation potential of BDD-generated radicals (•OH, SO4•¯, 1O2).
  • Electrochemical Cell Manufacturing: Provides performance benchmarks favoring BDD over conventional DSA (RuO2/IrO2-based) for radical-driven oxidation applications, guiding material selection for new reactor designs.
  • Energy Optimization in Water Treatment: Implementation of optimized operating conditions (derived from RSM) to ensure low energy consumption (low EE/O), reducing the operational cost of AOPs.
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

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2019 - Synthesis and application of stable, reusable TiO2 polymeric composites for photocatalytic removal of metronidazole: Removal kinetics and density functional analysis [Crossref]
  2. 2013 - Impact of pharmaceutical industry treated effluents on the water quality of river Uppanar, South east coast of India: A case study [Crossref]
  3. 2004 - Resistance in the environment [Crossref]
  4. 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
  5. 2019 - Degradation of metronidazole by UV/chlorine treatment: Efficiency, mechanism, pathways and DBPs formation [Crossref]
  6. 2013 - Simultaneous determination of metronidazole, chloramphenicol and 10 sulfonamide residues in honey by LC-MS/MS [Crossref]
  7. 2021 - Fabrication of magnetic CuFe2O4@PBC composite and efficient removal of metronidazole by the photo-Fenton process in a wide pH range [Crossref]
  8. 2022 - A novel ZnO/biochar composite catalysts for visible light degradation of metronidazole [Crossref]
  9. 2020 - Characterisation and bioremediation of wastewater: A review exploring bioremediation as a sustainable technique for pharmaceutical wastewater [Crossref]

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