Electrochemical Determination of Chemical Oxygen Demand Based on Boron-Doped Diamond Electrode
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-03-20 |
| Journal | Journal of Electrochemical Science and Technology |
| Authors | Dian S. Latifah, Subin Jeon, Ilwhan Oh |
| Institutions | Kumoh National Institute of Technology |
| Citations | 3 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research details the development and validation of a rapid, environment-friendly electrochemical sensor for Chemical Oxygen Demand (E-COD) utilizing a Boron-Doped Diamond (BDD) electrode.
- Core Value Proposition: The BDD-based E-COD sensor provides a fast (steady-state reached in ~10 seconds) and non-toxic alternative to the conventional dichromate method, which is slow (2-4 hours) and uses hazardous reagents (chromium, mercury).
- Mechanism: The BDD anode fully oxidizes organic pollutants, primarily via hydroxyl radicals (âąOH) generated at high anodic potential, resulting in a mass-transfer-limited steady-state current proportional to the COD concentration.
- Material Specification: The sensor employs a BDD thin film (3 ”m thick, 5000 ppm B doping) grown on a silicon substrate via Hot Filament CVD.
- Optimized Performance: Optimal analytical conditions were determined at an applied potential of 2.5 V (vs. SHE) and a neutral solution pH (range 3 to 10).
- Performance Metrics: The sensor exhibits a linear range of 0 to 80 mg/L and a low detection limit of 1.1 mg/L (S/N=5).
- Validation: The E-COD results show excellent correlation (R2=0.96) and high compatibility with the conventional dichromate COD method, with an average difference of only ~7%.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Anode Material | Boron-Doped Diamond (BDD) | - | Thin film grown on monocrystalline Si. |
| Boron Doping Level | 5000 | ppm | Used in HFCVD growth process. |
| Film Thickness | 3 | ”m | BDD layer thickness. |
| Resistivity | 100 | mΩ·cm | BDD film property. |
| Working Electrode Area | 2.54 | cm2 | Exposed area (18 mm diameter). |
| Optimized Applied Potential | 2.5 | V | vs. SHE (Selected for sensitive response and stability). |
| Optimized Solution pH | 3 to 10 | - | Neutral range (avoids excessive O2 evolution). |
| Linear Range (E-COD) | 0 to 80 | mg/L | Chemical Oxygen Demand (O2 equivalent). |
| Detection Limit (LOD) | 1.1 | mg/L | Calculated at S/N=5. |
| Steady-State Response Time | ~10 | seconds | Time to reach stable current after sample injection. |
| Correlation Coefficient (R2) | 0.96 | - | E-COD vs. Conventional Dichromate Method. |
| Calibration Equation (KHP standard) | E-COD = 123 Ă Inet | mg/L | Inet in mA. |
Key Methodologies
Section titled âKey Methodologiesâ- BDD Electrode Preparation: BDD thin film was grown on a thick monocrystalline Si substrate using the Hot Filament Chemical Vapor Deposition (HFCVD) method, achieving a 5000 ppm boron doping level.
- Cleaning and Activation: The electrode was degreased by sonication in acetone, isopropyl alcohol, and deionized water (10 minutes each), followed by surface treatment in 1.0 M HNO3 for one hour to remove impurities.
- Electrochemical Setup: Measurements were performed in a three-electrode cell configuration: BDD (working electrode), Pt coil (counter electrode), and Saturated Calomel Electrode (SCE) (reference electrode).
- Pre-conditioning: The BDD electrode was pre-conditioned by conducting 20 potential cycles in a blank 0.1 M KNO3 supporting electrolyte.
- Amperometric Detection: The E-COD value was determined using amperometric detection under well-stirred conditions. A constant potential (optimized at 2.5 V vs. SHE) was applied until the background current stabilized.
- Response Measurement: Aliquots of organic compounds were injected, and the resulting increase in steady-state anodic current (Inet) was measured as the sensor response, which is directly proportional to the COD concentration.
- Validation: E-COD results for model organic compounds (KHP, glucose, phenol, etc.) were compared against results obtained using the standard colorimetric dichromate digestion method (heating at 150 °C for 2 hours).
Commercial Applications
Section titled âCommercial ApplicationsâThe development of a rapid, robust, and non-toxic COD sensor based on BDD electrodes is highly relevant for several industries:
- Wastewater Treatment and Environmental Monitoring:
- Real-time, continuous monitoring of industrial and municipal effluent quality, replacing slow, centralized laboratory testing.
- Field-deployable, portable COD meters for rapid environmental surveys of rivers and lakes.
- Process Control in Manufacturing:
- Integration into chemical, pharmaceutical, and food processing plants to provide immediate feedback on organic load and water recycling efficiency.
- Advanced Electrochemical Oxidation Processes (EAOP):
- The BDD material, known for its wide potential window and high stability, is critical for high-efficiency electrochemical incineration and water remediation systems.
- Sensor Technology:
- Commercialization of compact, safer COD devices that eliminate the need for toxic reagents (e.g., chromium and mercury salts).
View Original Abstract
A rapid and environment-friendly electrochemical sensor to determine the chemical oxygen demand (COD) has been developed. The boron-doped diamond (BDD) thin-film electrode is employed as the anode, which fully oxidizes organic pollutants and provides a current response in proportion to the COD values of the sample solution. The BDD-based amperometric COD sensor is optimized in terms of the applied potential and the solution pH. At the optimized conditions, the COD sensor exhibits a linear range of 0 to 80 mg/L and the detection limit of 1.1 mg/L. Using a set of model organic compounds, the electrochemical COD sensor is compared with the conventional dichromate COD method. The result shows an excellent correlation between the two methods.