Degradation of pesticide Cartap in Padan 95SP by combined advanced oxidation and electro-Fenton process
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-05-06 |
| Journal | Journal of Solid State Electrochemistry |
| Authors | Nguyen Tien Hoang, Rudolf Holze |
| Institutions | Chemnitz University of Technology |
| Citations | 27 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive Summaryâ- Core Technology: Highly efficient degradation of the pesticide Cartap (Padan 95SP) achieved using a combined Advanced Oxidation Process (AOP) and Electro-Fenton (EF) system.
- Key Material: A Boron-Doped Diamond (BDD) thin-film electrode was employed as the anode to generate hydroxyl radicals (â˘OH) via water oxidation (BDD + H2O â BDD(â˘OH) + H+ + e-).
- Cartap Removal Efficiency: Near-quantitative removal of the parent Cartap molecule (>95%) was achieved rapidly, typically within the initial 5 minutes of electrochemical treatment.
- Mineralization Limitation: Total Organic Carbon (TOC) reduction was limited to approximately 80% under optimal conditions, indicating the formation of stable, recalcitrant organic intermediates that resist further â˘OH attack.
- Catalyst Performance: Copper ions (Cu2+) at 5 mM concentration significantly accelerated TOC removal in the early stages (first 30 min), outperforming the standard Fe2+ catalyst and other tested metals (Mg2+, Al3+).
- Pretreatment Impact: Pretreatment with NaOCl effectively removed Cartap but introduced chloride ions (Cl-), which negatively impacted the subsequent Electro-Fenton process efficiency by scavenging â˘OH radicals and complexing Fe2+/Fe3+ ions.
- Process Optimization: Optimal conditions were identified as 0.2 M H2O2 and 10 mM Fe2+ at an initial pH of 3.0, with a constant current density of 20 mA cm-2.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Initial Cartap Concentration | 700 | mg L-1 | Padan 95SP solution (2.6 mM) |
| Initial TOC Concentration | 215 | mg L-1 | Equivalent organic carbon content |
| Supporting Electrolyte | 0.05 | M | Na2SO4 |
| Current Density (j) | 20 | mA cm-2 | Constant current applied (optimal value) |
| Total Electrolysis Time | 120 | min | Duration of treatment |
| BDD Electrode Area | 3.8 | cm2 | Circular exposed surface area (Anode) |
| BDD Coating Thickness | 2.5 - 3 | Âľm | Diamond film thickness |
| Optimal Initial pH | 3.0 | - | Maintained throughout the EF process |
| Optimal H2O2 Concentration | 0.2 | M | Added for modified Electro-Fenton |
| Optimal Fe2+ Concentration | 10 | mM | Added catalyst concentration |
| Maximum TOC Removal | ~80 | % | Achieved after 120 min |
| Cartap Removal Time | < 5 | min | Time for near-complete parent molecule decomposition |
| Best Co-Catalyst (Initial Stage) | 5 mM Cu2+ | - | Achieved 35% TOC remaining after 5 min |
Key Methodologies
Section titled âKey Methodologiesâ- Electrochemical Cell: Bulk electrolysis conducted in a 400-mL, one-compartment cell at room temperature (22 °C).
- Electrode Configuration:
- Working Electrode (Anode): Boron-Doped Diamond (BDD) thin-film electrode (3.8 cm2).
- Counter Electrode (Cathode): Platinum foil.
- Reference Electrode: Ag/AgCl (sat. KCl).
- Electrolyte Preparation: 250 mL of 700 mg L-1 Padan 95SP solution prepared with 0.05 M Na2SO4 as the supporting electrolyte.
- Process Initiation: Solution pH was adjusted to the target value (typically pH 3.0) using H2SO4 or NaOH. H2O2 and Fe2+ (or other metal co-catalysts) were added to initiate the modified Electro-Fenton reaction.
- Operation Mode: Electrolysis was performed under galvanostatic control (constant current density) at 20 mA cm-2 for 120 minutes, with continuous magnetic stirring.
- Cartap Quantification: Cartap concentration was determined indirectly using UV-vis spectroscopy based on the 5,5-dithiobis-(2-nitrobenzoic acid) (DTNB) procedure, measuring the resulting thiolate anion at 412 nm.
- Mineralization Tracking: Total Organic Carbon (TOC) content was measured using a multi N/C 3100 NPOC analyzer to monitor the overall mineralization efficiency.
- Intermediate Analysis: High Performance Liquid Chromatography (HPLC) was used to analyze degradation products, confirming rapid Cartap decomposition and the appearance and subsequent fading of intermediate peaks.
Commercial Applications
Section titled âCommercial ApplicationsâThe use of BDD electrodes in combined AOP/Electro-Fenton systems is highly relevant for industrial and environmental engineering applications focused on water purification and detoxification:
- Pesticide and Herbicide Remediation: Direct application for treating agricultural runoff and wastewater contaminated with persistent, water-soluble pesticides like Cartap and related organosulfur compounds.
- Industrial Wastewater Treatment: Effective mineralization of complex, recalcitrant organic pollutants (POPs) in industrial effluents that are resistant to conventional biological or chemical methods.
- Advanced Water Purification Systems: Integration of BDD-based electrochemical reactors into tertiary treatment stages for municipal or industrial water recycling facilities requiring high levels of organic contaminant destruction.
- Electrochemical Reactor Design: Development of compact, high-efficiency, one-compartment electrochemical cells for simultaneous radical generation (anode) and catalyst regeneration (cathode), minimizing system complexity and footprint.
- Catalytic Oxidation Processes: Utilizing BDD technology to drive highly oxidative processes (like the combined EF/AOP) where the generation of powerful, non-selective oxidants (â˘OH radicals) is necessary for complete detoxification.
View Original Abstract
Abstract The electro-Fenton process combined with a boron-doped diamond-positive electrode in a one-compartment cell has shown efficient degradation of Cartap (95% in Padan 95SP) by hydroxyl radicals (â˘OH) generated in the electro-Fenton and the electrochemical oxidation processes. The influence of added NaOCl in a pretreatment step, effects of H 2 O 2 concentration, Fe 2+ -ion addition, presence of further metals acting as co-catalysts, and solution pH on the efficiency of Cartap degradation were studied. The concentration of Cartap was determined by UV-vis spectroscopy according to the 5,5-dithiobis-(2-nitrobenzoic acid) procedure. The efficiency reaches approximately 80% when measured as total carbon concentration decrease, even with increased concentrations of H 2 O 2 , Fe 2+ , or metal ions added as co-catalyst. This limitation is presumably due to recalcitrant intermediates, which cannot be destroyed by â˘OH.