| Metadata | Details |
|---|
| Publication Date | 2023-09-19 |
| Journal | Journal of the Mexican Chemical Society |
| Authors | Noe Valladares, Rubén Vázquez Medrano, Dorian Prato-García, Jorge G. Ibáñez |
| Institutions | Universidad Nacional de Colombia, Ibero American University |
| Citations | 1 |
| Analysis | Full AI Review Included |
- Core Technology: Advanced electro-oxidation utilizing a non-divided modified Diachem® cell equipped with a cathode-anode-cathode array of Boron-Doped Diamond (BDD) electrodes for herbicide mineralization.
- Performance Achieved: High removal efficiencies for the recalcitrant herbicide Bentazon (Bn), achieving up to 86% Bn removal, 68% Total Organic Carbon (TOC) removal, and 82% Chemical Oxygen Demand (COD) removal.
- Optimal Operating Point: The most efficient mineralization (TOC/COD) was achieved at a current density of 1.0 mA cm-2 and a volumetric flow of 750 mL min-1, using an initial Bn concentration of 100 mg L-1.
- Energy Efficiency: The specific energy consumption (ECTOC) under optimal conditions was minimized to 0.07 kWh gTOC-1, demonstrating high energy performance compared to other reported electrochemical processes.
- Process Greenness: Increasing the current density beyond 1.0 mA cm-2 (to 1.5 mA cm-2) yielded only marginal efficiency gains (2-3%) but increased the carbon footprint and treatment cost by 55%, confirming that low current density operation is critical for sustainable scaling.
- Kinetic Control: The Instantaneous Current Efficiency (ICE) showed an exponential reduction over time, indicating that the overall process efficiency is significantly limited by mass transfer kinetics, particularly at lower pollutant concentrations.
- Material Specifications: The BDD anodes featured a diamond layer thickness of 1-10 µm, resistivity of 0.1 Ω cm, and boron concentration ranging from 500 to 8000 ppm.
| Parameter | Value | Unit | Context |
|---|
| Anode Material | Boron-Doped Diamond (BDD) | N/A | Cathode-Anode-Cathode array |
| BDD Thickness | 1 to 10 | µm | Diamond conducting layer |
| BDD Resistivity | 0.1 | Ω cm | Electrode characteristic |
| Boron Concentration | 500 to 8000 | ppm | Doping level |
| Anode Geometrical Area | 100 | cm2 | Total active area |
| Optimal Current Density (j) | 1.0 | mA cm-2 | Best efficiency/cost ratio |
| Optimal Volumetric Flow (v) | 750 | mL min-1 | Highest mineralization |
| Initial Bn Concentration ([Bn]0) | 10, 50, 100 | mg L-1 | Tested range |
| Supporting Electrolyte | 0.04 M Na2SO4 / 0.05 M NaHSO4 | N/A | pH 2 ± 0.1 |
| Max Bn Removal | 86 | % | [Bn]0 = 100 mg L-1, j = 1.0 mA cm-2, v = 500 mL min-1 |
| Max TOC Removal | 68 | % | [Bn]0 = 100 mg L-1, j = 1.0 mA cm-2, v = 750 mL min-1 |
| Max COD Removal | 82 | % | [Bn]0 = 100 mg L-1, j = 1.0 mA cm-2, v = 750 mL min-1 |
| Minimum Specific Energy Consumption (ECTOC) | 0.07 | kWh gTOC-1 | Optimal conditions |
| Bn Oxidation Potential | 1.18 | V | vs. Ag/AgCl (determined by CV) |
| Bn Diffusion Coefficient (D) | 5.82 x 10-5 | cm2 s-1 | Calculated via Cottrell equation |
| Mexican Energy Mix Carbon Emission (Reference) | 0.068 | kg CO2 gTOC-1 | Used for cost/greenness analysis |
- Electrochemical Setup: Experiments were conducted in a closed flow system using a modified, non-divided Diachem® cell. The electrode configuration was a parallel cathode-anode-cathode array, designed to ensure homogeneous current distribution.
- Electrode Specifications: Boron-Doped Diamond (BDD) electrodes were used, characterized by low resistivity (0.1 Ω cm) and high boron doping (500 to 8000 ppm). The anode active area was 100 cm2.
- Electrolyte Preparation: The supporting electrolyte was an acidic buffer solution (pH 2 ± 0.1) composed of 0.04 M Na2SO4 and 0.05 M NaHSO4.
- Operational Variables: Three key variables were systematically tested:
- Current Density (j): 0.5, 1.0, and 1.5 mA cm-2.
- Initial Bentazon Concentration ([Bn]0): 10, 50, and 100 mg L-1.
- Volumetric Flow (v): 280, 500, and 750 mL min-1.
- Process Monitoring: Electrolysis lasted 330 minutes (5.5 h) at ambient temperature (avg. 24 °C). Samples were taken periodically to measure Bn concentration (UV-Vis spectrophotometry), mineralization (TOC), and oxidizability (COD).
- Performance Metrics: Process efficiency was quantified using the Instantaneous Current Efficiency (ICE) and the Specific Energy Consumption (ECTOC), allowing for direct comparison of operational costs and environmental impact across different conditions.
- Diffusion Coefficient Determination: Cyclic voltammetry and chronoamperometry, analyzed using the Cottrell equation, were employed to determine the Bn oxidation potential (1.18 V vs. Ag/AgCl) and the diffusion coefficient (5.82 x 10-5 cm2 s-1).
- Agrochemical Wastewater Treatment: Direct application in treating concentrated effluents from agricultural operations, particularly those generated during the cleaning or reuse of containers contaminated with persistent herbicides like Bentazon.
- Advanced Oxidation Processes (AOPs): Utilization of BDD anodes for generating highly potent hydroxyl radicals (BDD(OH)•), enabling the non-selective electrochemical incineration of complex, recalcitrant organic pollutants (e.g., pharmaceuticals, dyes, and other pesticides).
- Sustainable Remediation Systems: Integration of BDD electrochemical cells with renewable energy sources (e.g., solar photovoltaic or wind turbines) to minimize the carbon footprint and operating costs associated with high energy consumption processes.
- Industrial Water Recycling: Deployment in industrial settings requiring high-purity water, where BDD technology ensures high mineralization rates (up to 68% TOC removal) necessary for water reuse.
- Electrode Manufacturing (BDD): The study validates the performance requirements for BDD electrodes (low resistivity, high boron doping) optimized for high-efficiency electrochemical oxidation reactors.
View Original Abstract
Abstract. We studied the mineralization of the herbicide bentazon (Bn) through advanced electro-oxidation using a non-divided modified Diachem® cell. The treatment system consisted of an array of three boron-doped diamond (BDD) electrodes: cathode-anode-cathode. The chosen variables of interest were current density (j = 0.5, 1.0, and 1.5 mA cm-2), the initial Bn concentration (10, 50, and 100 mg L-1), and the volumetric flow (v = 280, 500, and 750 mL min-1). In all cases, a 0.04 M Na2SO4 and 0.05 M NaHSO4 (pH ~ 2) solution was used as the supporting electrolyte. Results indicate that, at low current densities, up to 86 % of the Bn present in the solution can be removed (j = 1.0 mA cm-2 and v = 500 mL min-1); however, additional increases in j (from 1.0 to 1.5 mA cm-2) slightly increase (2-3 %) the removal efficiency but increase 55 % the carbon footprint and the treatment cost. Likewise, increases in the volumetric flow from 500 to 750 mL min-1 marginally affect the elimination of Bn and the removal of total organic carbon (TOC) in 1% and 4 %, respectively. The highest efficiencies for TOC (68 %) and COD (82 %) removals were obtained with the following operational conditions: j = 1.0 mA cm-2 and v = 750 mL min-1. Values obtained for the instantaneous current efficiency (ICE) showed an exponential reduction, suggesting that mass transfer influences importantly the efficiency of the process. Resumen. En este trabajo se estudió la mineralización del herbicida bentazón (Bn) por medio de electroooxidación avanzada utilizando una celda no dividida Diachem® modificada. El sistema de tratamiento consta de un arreglo de tres electrodos de diamante dopado con boro (BDD): cátodo-ánodo-cátodo. Las variables de interés seleccionadas fueron: la densidad de corriente (j = 0.5, 1.0 y 1.5 mA cm-2), la concentración inicial de Bn (10, 50 y 100 mg L-1) y el flujo volumétrico (v = 280, 500 y 750 mL min-1). En todos los casos se usó como electrolito soporte una solución de 0.04 M Na2SO4 y 0.05 M de NaHSO4 (pH ~ 2). Los resultados obtenidos indican que, a bajas densidades de corriente, se puede remover hasta el 86 % del Bn presente en solución (j = 1.0 mA cm-2 y v = 500 mL min-1); sin embargo, aumentos adicionales en j (de 1.0 a 1.5 mA cm-2) elevan ligeramente la eficiencia de remoción (2-3 %) pero incrementan hasta en un 55% la huella de carbono y el costo de tratamiento. De igual forma, incrementos en el flujo volumétrico de 500 a 750 mL min-1 afectan de forma marginal la eliminación del Bn y la remoción del carbono orgánico total (TOC) en un 1 % y 4 %, respectivamente. Las mayores eficiencias de remoción de TOC (68 %) y COD (82 %) se obtuvieron con las siguientes condiciones operativas: j = 1.0 mA cm-2 y v = 750 mL min-1. Los valores obtenidos de la eficiencia de corriente instantánea (ICE) presentaron una reducción exponencial, lo cual sugiere que la transferencia de masa tiene una influencia importante en la eficiencia del proceso.