Electrocatalytic Oxidation of Toxic Wastewater using Electrodes based on Transition d-metal Oxides
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-01-08 |
| Journal | Water Air & Soil Pollution |
| Authors | Semra YaĆar Ăırak, Dilara ĂztĂŒrk, Abdurrahman Akyol |
| Citations | 3 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis study evaluates the electrocatalytic oxidation performance of various Dimensionally Stable Anodes (DSA) against the benchmark Boron Doped Diamond (BDD) electrode for treating Paracetamol (PCT) wastewater, focusing on a novel Ti/PbO2-IrO2-RuO2 composition.
- Benchmark Performance: BDD demonstrated superior mineralization efficiency in synthetic wastewater, achieving 96% Total Organic Carbon (TOC) removal and near-complete degradation of PCT and its toxic by-products (Benzoquinone/Hydroquinone).
- Best DSA Electrode: The Ti/PbO2-IrO2-RuO2 electrode was the most effective DSA tested, achieving 57% TOC removal in synthetic water, significantly outperforming other DSA types (e.g., Ti/IrO2-RuO2-TiO2 at 35%, Pt at 24%).
- Energy Efficiency: BDD provided the highest energy efficiency (2.32 %TOC removal per Watt). However, the Ti/PbO2-IrO2-RuO2 DSA electrode showed the best DSA efficiency (1.32 %TOC removal per Watt) and consumed similar total energy to BDD.
- Real Wastewater Challenge: Direct treatment of high-concentration real industrial PCT wastewater (TOC: 13,830 mg/L) failed due to electrode passivation; successful treatment required 1:10 dilution and filtration.
- Real Wastewater Results (Diluted): In 1:10 diluted real wastewater, the Ti/PbO2-IrO2-RuO2 DSA achieved 52% TOC removal, closely approaching BDDâs 58% removal, positioning it as a viable, cheaper alternative for practical application.
- Novelty: This paper is the first to study the electrooxidation of real PCT wastewater using the Ti/PbO2-IrO2-RuO2 DSA electrode.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Reactor Volume | 800 | mL | Experimental setup |
| Current Density | 350 | A/m2 | Applied operational condition |
| Initial pH (Synthetic) | 7 | - | Fixed starting condition |
| Initial Conductivity | 3500 | ”S/cm | Fixed starting condition |
| Treatment Time | 180 | minutes | Maximum duration for synthetic tests |
| Initial PCT Concentration (Synthetic) | 50 | mg/L | Synthetic wastewater composition |
| BDD TOC Removal Efficiency | 96 | % | Synthetic wastewater (Best performance) |
| Ti/PbO2-IrO2-RuO2 TOC Removal Efficiency | 57 | % | Synthetic wastewater (Best DSA performance) |
| BDD O2 Evolution Potential | 2.2 - 2.6 | V | High overoxidation potential (Inactive electrode) |
| PbO2-doped O2 Evolution Potential | 1.78 - 2.09 | V | DSA range |
| BDD Energy Efficiency (Synthetic) | 2.32 | %TOC/Watt | Highest efficiency |
| Ti/PbO2-IrO2-RuO2 Energy Efficiency (Synthetic) | 1.32 | %TOC/Watt | Best DSA efficiency |
| Real WW TOC (Initial) | 13,830 | mg/L | Industrial wastewater characterization |
| Real WW COD (Initial) | 69,200 | mg/L | Industrial wastewater characterization |
| Real WW Dilution Ratio | 1:10 | - | Required for successful treatment |
| BDD PCT Removal (1:10 Diluted WW) | 59 | % | Real wastewater performance |
| Ti/PbO2-IrO2-RuO2 PCT Removal (1:10 Diluted WW) | 53 | % | Real wastewater performance |
Key Methodologies
Section titled âKey MethodologiesâThe electrooxidation (EO) process was conducted using a comparative approach between BDD and five DSA electrodes under controlled conditions.
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Electrode Materials:
- Anodes Tested: BDD (Boron Doped Diamond), Pt, and five DSA compositions: Ti/PbO2-IrO2-RuO2, Ti/IrO2-RuO2-TiO2, Ti/RuO2-SnO2, Ti/IrO2-RuO2-SnO2.
- Cathode: Stainless steel electrode.
- Electrolyte: Sodium nitrate (NaNO3) used as the supporting electrolyte.
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Experimental Setup:
- EO was performed in an 800 mL plexiglass reactor (10x10x10 cm).
- Electrodes were placed 2 cm apart and the solution was mixed at 250 rpm to ensure homogeneous reaction conditions.
- Power was supplied by a 30 V-30A DC power supplier.
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Operational Parameters:
- Current density was fixed at 350 A/m2.
- Initial conductivity was fixed at 3500 ”S/cm.
- Initial pH was fixed at 7 (synthetic tests) or 7.4 (real wastewater tests).
- Experiments were run for 180 minutes (3 hours) at room temperature.
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Wastewater Preparation:
- Synthetic: Prepared with 50 mg/L PCT in ultra-pure water.
- Real Industrial: Purchased PCT wastewater (TOC: 13,830 mg/L; COD: 69,200 mg/L) required filtration and 1:10 dilution to prevent electrode passivation caused by high suspended solids and organic load.
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Analytical Methods:
- Mineralization: Total Organic Carbon (TOC) removal efficiency was measured using a SHIMADZU TOC-L analyzer.
- Pollutant/By-product Monitoring: PCT, Benzoquinone (BQ), and Hydroquinone (HQ) concentrations were monitored using UV-Vis spectrophotometry (244 nm, 293 nm, 288 nm, respectively) and HPLC analysis.
- Efficiency Calculation: Energy consumption (Watt) and TOC removal efficiency per unit energy (Watt) were calculated to compare economic viability.
- Toxicity Assessment: Toxicity was measured using the mortality of Daphnia magna on raw and treated wastewater samples at various dilution levels.
Commercial Applications
Section titled âCommercial ApplicationsâThe findings support the implementation of electrooxidation technology, particularly using optimized DSA electrodes, in industrial and municipal water treatment sectors.
- Pharmaceutical Wastewater Treatment: Direct application for the destruction and mineralization of persistent pharmaceutical micropollutants (like PCT) in effluent streams, ensuring compliance with discharge limits.
- Advanced Oxidation Processes (AOPs): Integration of the Ti/PbO2-IrO2-RuO2 DSA electrode as a cost-effective, high-performance alternative to BDD in AOP systems requiring high radical generation (âąOH).
- Industrial Effluent Management: Applicable for treating highly concentrated, complex industrial wastewaters, provided appropriate pre-treatment (filtration, dilution) is implemented to prevent electrode passivation.
- Hybrid Treatment Systems: Use of electrooxidation as an effective pre-treatment step (e.g., before biological reactors) to reduce toxicity and mineralize refractory compounds, improving the overall efficiency of sequential treatment trains.
- Electrode Technology Development: Validation of Pb-doped DSA electrodes as a promising class of materials that can approach the high overpotential and mineralization capability of BDD at a lower manufacturing cost.
View Original Abstract
Abstract The process of electrooxidation of the active substances Paracetamol (PCT), benzoquinone (BQ) and hydroquinone (HQ) was studied using a set of different dimensionally stable anode (DSA) and Boron doped diamond (BDD) electrodes. Comparison of the efficiency of electrocatalytic anodes was assessed using percent total organic carbon (%TOC) removal and PCT amount removal values. The removal of %TOC in synthetically prepared waters for the BDD anode reached 96%, for DSA electrodes Ti/PbO 2 -IrO 2 -RuO 2 57%, Ti/IrO 2 -RuO 2 -TiO 2 35%, Ti/IrO 2 -RuO 2 -SnO 2 31%, Ti/RuO 2 -SnO 2 30% and Pt 24%. BDD effectively degrades PCT and almost completely mineralizes BQ and HQ. A DSA-Ti/PbO 2 -IrO 2 -RuO 2 electrode and a BDD electrode were used in the electrooxidation process of real industrial wastewater containing PCT. The BDD electrode had a TOC removal efficiency of 58%, while the DSA-Ti/PbO 2 -IrO 2 -RuO 2 electrode achieved 52%. Despite similar values ââof PCT removal by both electrodes, the Ti/PbO 2 -IrO 2 -RuO 2 anode showed low mineralization of organic matter. The originality of this paper lies in the study of the electrooxidation of real PCT wastewater and the use of a Ti/PbO 2 -IrO 2 -RuO 2 electrode. Graphical Abstract