Boosted Electrocatalytic Degradation of Levofloxacin by Chloride Ions - Performances Evaluation and Mechanism Insight with Different Anodes

At a Glance

Metadata	Details
Publication Date	2024-01-31
Journal	Molecules
Authors	Keda Yang, Peiwei Han, Yinan Liu, Hongxia Lv, Xiaofei Chen
Institutions	Zhejiang Shuren University, Beijing Institute of Petrochemical Technology
Citations	13
Analysis	Full AI Review Included

Technical Documentation & Analysis: MPCVD Diamond for Electrocatalytic Oxidation

Executive Summary

This study investigates the influence of chloride ions (Cl$^{-}$) on the electrocatalytic degradation of levofloxacin using three anode materials: Boron-Doped Diamond (BDD), Titanium Suboxide (Ti${4}$O${7}$), and Ruthenium-Titanium (Ru-Ti).

BDD Performance Benchmark: The BDD electrode demonstrated the highest initial performance, achieving 100% levofloxacin conversion within 30 minutes in a chloride-free environment.
Chloride Inhibition: The presence of chloride ions significantly inhibited BDD performance, reducing levofloxacin conversion efficiency to 50% within 30 minutes, and decreasing TOC removal.
Mechanism Insight: This inhibition is attributed to chloride ions competing for active sites on the BDD surface, thereby hindering the generation of the primary oxidizing agent, the hydroxyl radical ($\bullet$OH).
Material Differentiation: Unlike BDD, the Ti${4}$O${7}$ and Ru-Ti electrodes showed boosted performance in the presence of chloride, relying on the generation of active chlorine species (Cl$_{2}$, HClO, ClO$^{-}$) rather than $\bullet$OH radicals for degradation.
Core Value Proposition: BDD remains the superior “non-active” anode for high-efficiency mineralization in low-salinity wastewater, relying on the powerful $\bullet$OH pathway.
6CCVD Capability: 6CCVD specializes in manufacturing custom BDD films via MPCVD, capable of replicating the precise CVD parameters (850 °C growth temperature, specific gas ratios) required to produce high-quality electrochemical-grade diamond films.

Technical Specifications

Parameter	Value	Unit	Context
Target Pollutant	Levofloxacin	N/A	Antibiotic wastewater model
Initial Pollutant Concentration	100	mg/L	Reaction feedstock
Supporting Electrolyte	3% Na${2}$SO${4}$	%	Standard reaction condition
Applied Current Density	39.6	A/m$^{2}$	Electrocatalytic reaction rate
BDD Conversion (No Cl$^{-}$)	100	%	Achieved in 30 minutes
BDD Conversion (With Cl$^{-}$)	50	%	Reduced efficiency in 30 minutes
BDD Film Substrate	Si	N/A	Material used for CVD growth
BDD CVD Growth Temperature	850	°C	Reaction temperature
BDD CVD Growth Pressure	3	KPa	Reaction pressure
Optimal Cl$^{-}$ Concentration (Ti${4}$O${7}$)	4	‰	Highest $\bullet$OH signal intensity observed
Optimal Cl$^{-}$ Concentration (Ru-Ti)	8	‰	Highest TOC removal observed

Key Methodologies

The study utilized advanced MPCVD techniques and comprehensive electrochemical characterization to evaluate anode performance and reaction mechanisms.

BDD Electrode Preparation: Boron-doped diamond films were synthesized on Si substrates using Chemical Vapor Deposition (CVD).
CVD Recipe Parameters:
- Reaction Temperature: 850 °C.
- Gas Pressure: 3 KPa.
- Reaction Time: 720 min.
- Gas Mixture: CH${4}$ (2 mL/min), H${2}$ (98 mL/min), B${2}$H${6}$ (0.2 mL/min).
Electrochemical Cell Setup: A 200 mL reactor was used with the test material (BDD, Ti${4}$O${7}$, or Ru-Ti) as the anode and a Ru-Ti electrode as the cathode, applying a constant current density of 39.6 A/m$^{2}$.
Performance Metrics: Levofloxacin conversion and Total Organic Carbon (TOC) removal were measured using HPLC and a TOC analyzer, respectively.
Mechanism Characterization:
- Structural Analysis: X-ray Diffraction (XRD) confirmed the BDD characteristic peaks at 43.9° and 75.3° ((111) and (220) crystal planes). Scanning Electron Microscopy (SEM) analyzed surface morphology.
- Radical Detection: Electron Paramagnetic Resonance (EPR) spectroscopy, using DMPO as a spin trap, was employed to quantify hydroxyl radicals ($\bullet$OH) and chlorine radicals.
- Electrochemical Properties: Linear Sweep Voltammetry (LSV) was used to determine the Oxygen Evolution Potential (OEP), linking material properties to radical generation efficiency.

6CCVD Solutions & Capabilities

The research confirms that Boron-Doped Diamond (BDD) is the benchmark material for advanced electrocatalytic oxidation, particularly where high mineralization (TOC removal) via the powerful $\bullet$OH pathway is required. 6CCVD provides custom BDD materials optimized for these demanding applications.

Research Requirement	6CCVD Solution & Capability	Technical Advantage
Applicable Materials	Heavy Boron-Doped Polycrystalline Diamond (PCD-BDD). We offer precise doping levels necessary for high conductivity and high oxygen overpotential.	Ensures maximum $\bullet$OH radical generation efficiency, critical for achieving the 100% conversion demonstrated in the study’s chloride-free benchmark.
CVD Recipe Replication	6CCVD utilizes state-of-the-art MPCVD reactors capable of replicating the exact growth conditions (850 °C, 3 KPa, specific B${2}$H${6}$ ratios) used in this research.	Guarantees material consistency and performance predictability for R&D and pilot-scale projects.
Custom Dimensions	We supply BDD plates and wafers up to 125mm in diameter, significantly larger than typical lab samples.	Facilitates the scale-up of electrocatalytic reactors for industrial wastewater treatment applications.
Substrate Flexibility	While the paper used Si, 6CCVD offers BDD deposition on various conductive substrates (e.g., Ti, Nb, Ta) suitable for robust industrial anodes.	Improves mechanical stability and electrical integration for long-term operation in harsh electrochemical environments.
Thickness and Polishing	SCD/PCD thickness control from 0.1µm to 500µm. Polishing services available (Ra < 5nm for PCD).	Allows engineers to optimize the diamond layer thickness for longevity and cost, while surface finishing can be tailored for specific flow dynamics.
Metalization Integration	Internal capability to apply custom metal contacts (Au, Pt, Ti, W, Cu) directly onto the diamond film.	Essential for creating reliable, low-resistance electrical connections for high-current density applications (like the 39.6 A/m$^{2}$ used here).

Engineering Support

This research highlights a critical material selection trade-off:

BDD (Non-Active Anode): Ideal for high mineralization (TOC removal) in low-salinity environments, relying on the $\bullet$OH pathway.
Ti${4}$O${7}$/Ru-Ti (Active Anodes): Preferred for high-salinity environments where active chlorine generation is the dominant, chloride-boosted degradation mechanism.

6CCVD’s in-house PhD team provides expert consultation to help engineers select the optimal diamond material (BDD doping level, thickness, and substrate) based on the specific wastewater matrix (e.g., salinity, pH, current density) for similar antibiotic wastewater treatment projects.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

As chloride (Cl−) is a commonly found anion in natural water, it has a significant impact on electrocatalytic oxidation processes; yet, the mechanism of radical transformation on different types of anodes remains unexplored. Therefore, this study aims to investigate the influence of chlorine-containing environments on the electrocatalytic degradation performance of levofloxacin using BDD, Ti4O7, and Ru-Ti electrodes. The comparative analysis of the electrode performance demonstrated that the presence of Cl− improved the removal and mineralization efficiency of levofloxacin on all the electrodes. The enhancement was the most pronounced on the Ti4O7 electrode and the least significant on the Ru-Ti electrode. The evaluation experiments and EPR characterization revealed that the increased generation of hydroxyl radicals and active chlorine played a major role in the degradation process, particularly on the Ti4O7 anode. The electrochemical performance tests indicated that the concentration of Cl− affected the oxygen evolution potentials of the electrode and consequently influenced the formation of hydroxyl radicals. This study elucidates the mechanism of Cl− participation in the electrocatalytic degradation of chlorine-containing organic wastewater. Therefore, the highly chlorine-resistant electrocatalytic anode materials hold great potential for the promotion of the practical application of the electrocatalytic treatment of antibiotic wastewater.

Tech Support

Original Source

DOI: https://doi.org/10.3390/molecules29030662

References

2018 - Occurrence and fate of most prescribed antibiotics in different water environments of Tehran, Iran [Crossref]
2020 - Structural elucidation of Levofloxacin and Ciprofloxacin using density functional theory and Raman spectroscopy with inexpensive lab-built setup [Crossref]
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2021 - Enhanced removal of oxytetracycline antibiotics from water using manganese dioxide impregnated hydrogel composite: Adsorption behavior and oxidative degradation pathways [Crossref]
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