Chlorpyrifos removal - Nb/boron-doped diamond anode coupled with solid polymer electrolyte and ultrasound irradiation

At a Glance

Metadata	Details
Publication Date	2020-10-09
Journal	Journal of Environmental Health Science and Engineering
Authors	Andrea Luca Tasca, Davide Clematis, Marco Panizza, Sandra Vitolo, Monica Puccini
Institutions	University of Pisa, University of Genoa
Citations	9
Analysis	Full AI Review Included

Technical Documentation & Analysis: MPCVD Diamond for Advanced Oxidation Processes

Executive Summary

This research successfully demonstrates the efficacy of Boron-Doped Diamond (BDD) anodes coupled with a Solid Polymer Electrolyte (SPE) for the advanced oxidation and removal of Chlorpyrifos (CP), a persistent organic pollutant. 6CCVD is uniquely positioned to supply the high-performance BDD materials required to replicate and scale this technology.

High Efficiency: Achieved up to 89.28% removal of Chlorpyrifos (CP) in 30 minutes using anodic oxidation at 0.1 A, confirming BDD’s superior capability for hydroxyl radical (•OH) generation.
Low Conductivity Solution Processing: The use of a Solid Polymer Electrolyte (SPE) membrane (Nafion® N324) successfully overcame the challenge of treating low-conductivity aqueous streams, opening pathways for pharmaceutical and personal care product remediation.
Material Stability: The Nb/BDD anode demonstrated excellent stability, with the conductive diamond layer showing no significant deterioration or passivation phenomena during the process.
Mass Transport Limitation: The study identified mass transport near the anode surface as the critical limiting factor, suggesting that optimization of electrode geometry and stirring rate is necessary for industrial scale-up.
Scalability Potential: The SPE technology and BDD anode combination is highly promising for in-situ groundwater remediation and industrial water treatment facilities, offering a sludge-free alternative to conventional methods.

Technical Specifications

The following hard data points were extracted from the experimental setup and results, focusing on the electrochemical parameters and performance metrics.

Parameter	Value	Unit	Context
Anode Material	Nb/BDD	N/A	Boron-Doped Diamond (BDD)
Cathode Material	Ti/RuO₂ mesh	N/A	Counter electrode
Electrode Dimensions	3.5 x 7.5	cm	Active area size
Electrode Gap	0.15	mm	Distance maintained by SPE
Initial CP Concentration	0.56	µg L^-1	Target pollutant concentration
Current Intensity Tested	0.1 and 0.5	A	Galvanostatic operation
Sonication Frequency	40	kHz	Used for coupled AOP trials
Maximum CP Removal	89.28	%	Achieved at 0.1 A (100 mA) in 30 min
Lowest Specific Energy Consumption	8.68·10^-6	KWh µg^-1 removed	At 100 mA, 10 min (Sonication Off)
Highest Specific Energy Consumption	2.33·10^-3	KWh µg^-1 removed	At 500 mA, 30 min (Sonication On)
Key By-products Detected	TCP, OCP	µg L^-1	3,5,6-trichloro-2-pyridinol and OCP

Key Methodologies

The experiment utilized a novel sono-electrochemical reactor design optimized for low-conductivity solutions.

Electrode Pre-treatment: Prior to each galvanostatic electrolysis assay, the Nb/BDD anode and Ti/RuO₂ cathode were sonicated for 30 minutes at a current intensity of 1 A to ensure surface cleanliness and remove impurities.
Reactor Configuration: A single-compartment electrochemical cell was constructed using the Nb/BDD anode and Ti/RuO₂ mesh cathode, separated by a Nafion® N324 ion exchange membrane (SPE) fixed at a 0.15 mm gap.
Solution Parameters: Aqueous CP solutions (0.56 µg L^-1) were treated at 20 °C and natural pH, maintained mixed by a vertical stirrer operating at 550 rpm.
Electrochemical Operation: Trials were conducted under galvanostatic control using an AMEL 2055 potentiostat/galvanostat, testing current intensities of 0.1 A (100 mA) and 0.5 A (500 mA) for 30 minutes.
Sonication Integration: Ultrasound irradiation was applied at 40 kHz using a dedicated ultrasonic bath (SONICA 2200) for coupled sono-electrolysis experiments.
Analysis: Degradation and by-product formation were monitored using Gas Chromatography-Mass Spectrometry (GC-MS).

6CCVD Solutions & Capabilities

The successful implementation of this advanced oxidation process hinges on the quality and customization of the Boron-Doped Diamond (BDD) electrode. 6CCVD provides the necessary materials and engineering support to scale this research for industrial and environmental applications.

Applicable Materials

To replicate and extend this research, high-quality, heavily doped BDD is essential for maximizing hydroxyl radical generation and minimizing passivation.

Heavy Boron-Doped Diamond (BDD) Plates: 6CCVD specializes in MPCVD BDD, offering superior electrochemical stability and high overpotential for oxygen evolution, crucial for efficient AOPs like the one demonstrated.
Polycrystalline Diamond (PCD) Substrates: For large-area industrial reactors, 6CCVD can provide large-format PCD wafers (up to 125mm) that can be subsequently doped to create large-scale BDD electrodes, optimizing cost and throughput.
Single Crystal Diamond (SCD) (Reference Grade): While BDD is the primary material, 6CCVD offers ultra-pure SCD plates (Ra < 1nm) for fundamental research requiring highly controlled, defect-free diamond surfaces for mechanistic studies.

Customization Potential

The paper utilized specific electrode dimensions (3.5 cm x 7.5 cm) and a Nb/BDD configuration. 6CCVD’s custom manufacturing capabilities directly address these requirements, enabling rapid prototyping and industrial scaling.

Requirement from Paper	6CCVD Customization Capability	Technical Advantage
Specific Dimensions (3.5 cm x 7.5 cm)	Custom laser cutting and shaping of BDD plates/wafers.	Allows precise replication of lab-scale geometry and optimization for flow reactors.
Nb/BDD Anode	Full internal metalization services (Au, Pt, Pd, Ti, W, Cu).	We can deposit custom metal contacts (e.g., Ti/Pt/Au stack) or backing layers to ensure optimal current distribution and mechanical stability, replacing or enhancing the Nb backing used in the study.
Mass Transport Optimization	Custom thickness BDD (0.1µm to 500µm) and substrates (up to 10mm).	Enables the design of novel 3D electrode structures or thin-film BDD coatings on conductive substrates to maximize surface area and mitigate mass transport limitations.
Surface Finish	Polishing down to Ra < 5nm for inch-size PCD/BDD.	Ensures consistent surface morphology for reproducible electrochemical performance and long electrode lifetime.

Engineering Support

The research highlights that mass transport limitations and energy consumption are key challenges for scaling up sono-electrochemical AOPs.

AOP Optimization Consultation: 6CCVD’s in-house PhD team provides expert consultation on material selection and electrode design for similar Water Remediation and Anodic Oxidation projects. We assist engineers in defining the optimal doping level, thickness, and geometry of BDD electrodes to balance radical generation efficiency with energy consumption.
Electrode Lifetime and Stability: We offer accelerated testing and analysis to ensure the BDD material meets the required operational lifetime under high current density and aggressive chemical environments.
Global Supply Chain: We offer reliable global shipping (DDU default, DDP available) to ensure rapid delivery of custom BDD materials worldwide, supporting continuous research and development efforts.

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

Tech Support

Original Source

DOI: https://doi.org/10.1007/s40201-020-00555-z