Metronidazole Electro-Oxidation Degradation on a Pilot Scale

At a Glance

Metadata	Details
Publication Date	2024-12-31
Journal	Catalysts
Authors	Sandra Maldonado, Carlos Barrera-Díaz, Patricia Balderas‐Hernández, Deysi Amado-Piña, Teresa Torres-Blancas
Institutions	Tecnológico Nacional de México, Instituto Tecnológico de Toluca
Citations	3
Analysis	Full AI Review Included

Technical Documentation & Analysis: MPCVD Diamond for Advanced Oxidation Processes

Executive Summary

This documentation analyzes the successful pilot-scale degradation of Metronidazole (MTZ) using a Boron-Doped Diamond (BDD) anode in an electro-oxidation Advanced Oxidation Process (AOP). The findings strongly validate the use of high-quality MPCVD BDD for industrial wastewater pre-treatment.

100% Degradation Achieved: Complete removal of 30 mg L^-1 MTZ was achieved within 180 minutes using a BDD anode at a current density of 100 mA cm^-2.
High Efficiency Material: The BDD electrode, characterized by a 2.83 µm thickness and 500 mg·dm^-3 boron content, enabled the continuous generation of highly reactive hydroxyl radicals (•OH).
Enhanced Biodegradability: The treatment significantly increased the biodegradability index (BOD₅/COD) from 0.67 (low) to 0.93 (highly biodegradable) at 100 mA cm^-2, making the effluent suitable for conventional biological plants.
Energetic Viability: The process demonstrated low specific energy consumption (E_c) of 0.049 kWh m^-3 for the highest efficiency treatment, confirming the economic viability of BDD-based AOPs at pilot scale.
Scaling Potential: The pilot-scale results (16 L volume) provide critical data for optimizing electrode configuration and scaling up BDD technology for industrial and municipal wastewater applications.

Technical Specifications

The following hard data points were extracted from the pilot-scale electro-oxidation experiments utilizing the BDD anode:

Parameter	Value	Unit	Context
Anode Material	Boron-Doped Diamond (BDD)	N/A	DiaClean® cell
BDD Boron Content	500	mg·dm^-3	Diamond coating specification
BDD Thickness	2.83	µm	Diamond coating specification
Anode Surface Area	78.54	cm²	Disc geometry
Inner Electrode Gap	5	mm	Cell configuration
Solution Volume	16	L	Pilot-scale batch system
Initial MTZ Concentration	30	mg L^-1	Wastewater simulation
Max Current Density Tested	100	mA cm^-2	Galvanostatic operation
Max MTZ Degradation (180 min)	100	%	Achieved at 100 mA cm^-2
Max TOC Mineralization (180 min)	29.9	%	Achieved at 100 mA cm^-2
Max Biodegradability Index (BOD₅/COD)	0.93	N/A	Achieved at 100 mA cm^-2
Highest Reaction Constant (k₁)	0.0258	min^-1	Pseudo-first order kinetics at 100 mA cm^-2
Specific Energy Consumption (E_c)	0.049063	kWh m^-3	At 100 mA cm^-2 (3 h treatment)

Key Methodologies

The electro-oxidation process was conducted under controlled galvanostatic conditions in a recirculating batch system to evaluate the performance of the BDD anode.

Electrochemical Cell Setup: A DiaClean® cell (Model 101) was employed, featuring a BDD anode and a stainless-steel cathode, separated by a 5 mm inner electrode gap.
BDD Anode Specification: The BDD coating was 2.83 µm thick, applied to a silicon substrate, with a high boron content of 500 mg·dm^-3 and an active surface area of 78.54 cm².
Solution Composition: Experiments utilized 16 L of aqueous solution containing 30 mg L^-1 MTZ, supported by 0.05 M Na₂SO₄ as the electrolyte.
Operating Conditions: The system was run at room temperature (pH 7 ± 0.5) for 180 minutes (3 hours) under galvanostatic control.
Current Density Variation: Three distinct current densities were tested to optimize degradation kinetics: 30 mA cm^-2, 50 mA cm^-2, and 100 mA cm^-2.
Recirculation Rate: The solution was continuously recirculated at a high flow rate of 286.92 L h^-1 to ensure uniform treatment.
Analytical Monitoring: Degradation was tracked using Ultra-High-Performance Liquid Chromatography (UHPLC). Mineralization and water quality were assessed via Total Organic Carbon (TOC) analysis and Biochemical Oxygen Demand (BOD₅) determination (ISO 5815).

6CCVD Solutions & Capabilities

The successful implementation of this pilot-scale AOP relies entirely on the quality and precise specification of the Boron-Doped Diamond (BDD) anode. 6CCVD is uniquely positioned to supply BDD materials that meet or exceed the requirements for replicating and scaling this advanced wastewater treatment technology.

Applicable Materials

To replicate or extend this research for industrial scale-up, the following 6CCVD material is required:

Heavy Boron Doped Polycrystalline Diamond (PCD) Wafers: Our MPCVD process delivers highly conductive BDD films, essential for achieving the high overpotential required for efficient hydroxyl radical generation (Equation 1, Page 6). We can precisely match the required 500 mg·dm^-3 boron content and control the sp³/sp² ratio for maximum electrochemical stability and efficiency.

Customization Potential

The paper utilized a specific disc geometry (78.54 cm²) and thickness (2.83 µm). 6CCVD offers full customization capabilities critical for optimizing BDD electrodes for commercial viability:

Research Requirement	6CCVD Customization Capability	Benefit to Client
Electrode Dimensions (78.54 cm² disc)	Custom Plates/Wafers up to 125mm (PCD) and precision laser cutting services.	We supply BDD electrodes in exact disc, square, or custom geometries, ready for integration into DiaClean® or proprietary cell designs.
Diamond Thickness (2.83 µm)	Precise thickness control for PCD from 0.1 µm to 500 µm.	Allows engineers to fine-tune the diamond layer thickness and doping profile to optimize current density performance (up to 100 mA cm^-2) and minimize material cost.
Electrode Integration	Custom substrate preparation and internal metalization services (Au, Pt, Ti, W).	We provide fully finished BDD electrodes, metalized for robust electrical contact and integration into high-flow reactor stacks, addressing the scaling challenges noted in the paper.
Surface Finish	Polishing capability for PCD to Ra < 5nm (Inch-size).	Ensures minimal surface defects, maximizing active sites for •OH generation and extending electrode lifespan in aggressive AOP environments.

Engineering Support

6CCVD’s in-house PhD team specializes in the material science of electrochemical systems. We can assist researchers and industrial partners with:

Material Selection: Consulting on optimal boron concentration and diamond thickness to maximize the kinetic reaction constant (k₁) for specific Advanced Oxidation Process (AOP) projects targeting recalcitrant pollutants like MTZ.
Scale-Up Optimization: Providing guidance on electrode array design and material specifications necessary to transition from pilot-scale batch systems (16 L) to high-volume, continuous-flow industrial reactors, ensuring cost-effective operation (low E_c).
Global Logistics: Offering global shipping (DDU default, DDP available) to ensure timely delivery of custom BDD materials worldwide.

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

View Original Abstract

In this investigation, metronidazole was degraded in an aqueous solution through electro-oxidation. A DiaClean® cell was used to accommodate a stainless-steel electrode as a cathode and a boron-doped diamond (BDD) electrode as anode. This setup provides several electrochemical advantages, including low currents, a high operational potential, and, frequently, low adsorption compared to conventional carbon materials. The physicochemical parameters were estimated after 180 min of treatment, applying different current densities. The concentration of metronidazole was monitored by HPLC to assess degradation, resulting in 30.67% for 30 mA cm−2, 79.4% for 50 mA cm−2, and 100% for 100 mA cm−2. The TOC mineralization percentages were 12.71% for 30 mA cm−2, 14.8% for 50 mA cm−2, and 29.9% for 100 mA cm−2. Also, biodegradability indices of 0.70 for 30 mA cm−2, 0.81 for 50 mA cm−2, and 0.93 for 100 mA cm−2 were obtained. The byproducts found were formic acid and acetic acid. A pseudo-first order kinetic model was thus obtained due to the quasi-stable concentration achieved through hydroxyl radicals, given that they do not accumulate in the medium, due to their high rate of destruction and short lifespan.

Tech Support

Original Source

DOI: https://doi.org/10.3390/catal15010029

References

2019 - A Statistical Model and DFT Study of the Fragmentation Mechanisms of Metronidazole by Advanced Oxidation Processes [Crossref]
2018 - Electrochemical detection and removal of pharmaceuticals in waste waters [Crossref]
2019 - Degradation of chloramphenicol and metronidazole by electro-Fenton process using graphene oxide-Fe3O4 as heterogeneous catalyst [Crossref]
2020 - Photocatalytic degradation of metronidazole (MNZ) antibiotic in aqueous media using copper oxide nanoparticles activated by H2O2/UV process: Biodegradability and kinetic studies [Crossref]
2019 - The Comparison of ZnO/polyaniline Nanocomposite under UV and Visible Radiations for Decomposition of Metronidazole: Degradation Rate, Mechanism and Mineralization [Crossref]
2016 - Gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode as a sensitive voltammetric sensor for the determination of diclofenac sodium [Crossref]
2019 - Electroanalysis of Pharmaceuticals on Boron-Doped Diamond Electrodes: A Review [Crossref]
2013 - Degradation of Metronidazole in Aqueous Solution by Electrochemical Peroxidation [Crossref]
2018 - Electrochemical treatment of pharmaceutical wastewater through electrosynthesis of iron hydroxides for practical removal of metronidazole [Crossref]
2015 - Photocatalytic degradation of Metronidazole with illuminated TiO2 nanoparticles [Crossref]