Chlorpyrifos removal - Nb/boron-doped diamond anode coupled with solid polymer electrolyte and ultrasound irradiation
At a Glance
Section titled âAt a Glanceâ| 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 |
Executive Summary
Section titled âExecutive Summaryâ- Novel Reactor Design: A sono-electrochemical reactor was developed utilizing a Niobium/Boron-Doped Diamond (Nb/BDD) anode coupled with a Solid Polymer Electrolyte (SPE) (NafionÂź N324) to degrade Chlorpyrifos (CP).
- High Removal Efficiency: Anodic oxidation alone achieved up to 89.28% CP removal in 30 minutes at a low current intensity (0.1 A), demonstrating superior performance compared to previously reported methods for low-conductivity solutions.
- SPE Success: The SPE membrane successfully facilitated the electrochemical process in low-conductivity aqueous media (initial CP concentration: 0.56 ”g L-1), overcoming a major limitation of conventional electro-oxidation.
- Degradation Pathway: CP degradation proceeds via oxidation and hydrolysis, generating 3,5,6-trichloro-2-pyridinol (TCP) and O,O-Diethyl O-(3,5,6-trichloropyridin-2-yl) phosphate (OCP) as primary intermediates.
- Sonication Ineffectiveness: Ultrasound irradiation (40 kHz) did not enhance CP removal efficiency and significantly increased the specific energy consumption (up to 26x), indicating that mass transport limitations near the anode surface were the dominant kinetic constraint.
- Future Potential: The BDD/SPE technology is highly promising for the remediation of emerging pollutants (pharmaceuticals, pesticides) in low-conductivity industrial streams and for in-situ groundwater treatment, offering a sludge-free oxidation alternative.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Anode Material | Nb/Boron-Doped Diamond (BDD) | N/A | High hydroxyl radical generation |
| Cathode Material | Ti/RuO2 mesh | N/A | Used for hydrogen evolution |
| Electrolyte Type | NafionÂź N324 | N/A | Solid Polymer Electrolyte (SPE) |
| Electrode Dimensions | 3.5 x 7.5 | cm | Active surface area |
| Electrode Gap | 0.15 | mm | Distance between anode and cathode |
| Initial CP Concentration | 0.56 ± 0.005 | ”g L-1 | Low concentration test solution |
| Current Intensities Tested | 0.1 and 0.5 | A | Galvanostatic operation |
| Sonication Frequency | 40 | kHz | Ultrasonic irradiation |
| Max CP Removal (0.1 A, 30 min) | 89.28 | % | Sonication Off |
| Min Specific Energy Consumption | 8.68·10-6 | kWh ”g-1 removed | 0.1 A, 10 min, Sonication Off |
| Max Specific Energy Consumption | 2.33·10-3 | kWh ”g-1 removed | 0.5 A, 30 min, Sonication On |
| Stirring Rate | 550 | rpm | Vertical stirrer mixing |
| Operating Temperature | 20 | °C | Ambient conditions |
Key Methodologies
Section titled âKey Methodologiesâ- Reactor Configuration: Experiments were conducted in a single-compartment electrochemical cell using a Nb/BDD anode and a Ti/RuO2 mesh cathode, separated by a NafionÂź N324 Solid Polymer Electrolyte (SPE) membrane.
- Electrolysis Conditions: Trials were performed under galvanostatic control (0.1 A and 0.5 A) for 30 minutes at 20 °C and natural pH, powered by an AMEL 2055 potentiostat/galvanostat.
- Mixing and Pre-treatment: Solutions were continuously mixed at 550 rpm. Electrodes were pre-sonicated for 30 minutes at 1 A prior to each assay to ensure surface cleanliness.
- Sono-Electrolysis Coupling: Sonication was applied using a SONICA 2200 ultrasonic device operating at 40 kHz during coupled trials.
- Extraction and Analysis: Samples were collected at defined intervals, stored in the dark at 4 °C, and extracted using rotary evaporation with a cyclohexane/ethylacetate mixture (1:1).
- Quantification: CP and its metabolites (TCP, OCP) were quantified using a Shimadzu GC-MS-TQ8040 equipped with a crossbond diphenyl dimethyl polysiloxane SH-Rxi-5 ms column.
Commercial Applications
Section titled âCommercial Applicationsâ- Advanced Oxidation Processes (AOPs): Integration of BDD anodic oxidation into tertiary water treatment facilities to achieve high mineralization rates for persistent organic pollutants (POPs) and emerging contaminants.
- Low-Conductivity Wastewater Treatment: Specialized remediation systems for industrial streams (e.g., pharmaceutical manufacturing, chemical synthesis) characterized by low ionic strength, where traditional electrochemical methods fail.
- Solid Polymer Electrolyte (SPE) Systems: Development of compact, energy-efficient electrochemical cells utilizing SPE technology for decentralized or mobile water purification units, eliminating the need for added supporting electrolytes.
- Diamond Electrode Supply: Increased demand for high-performance, stable Nb/BDD electrodes for industrial electrochemical applications requiring robust hydroxyl radical generation and resistance to passivation.
- In-Situ Groundwater Remediation: Application of BDD/SPE reactors for the direct treatment of contaminated groundwater containing pesticides (like Chlorpyrifos) and personal care products, offering a sludge-free, in-situ solution.