Advanced Oxidation of Organic Dyes Using a Porous Gold Electrode - Kinetic Analysis
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-04-01 |
| Journal | An-Najah University Journal for Research - A (Natural Sciences) |
| Authors | Fatima Zaaboul, Chaimaa Haoufazane, Mohamed El Ouardi, Meryem Abouri, Khalil Azzaoui |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research validates the use of a porous gold electrode (PGE) in an electrochemical advanced oxidation process (EAOP) for highly efficient degradation of the azo dye Reactive Blue 203 (RB203).
- Core Value Proposition: The PGE demonstrated exceptional stability and electrocatalytic activity, achieving high mineralization rates, positioning it as a sustainable alternative to conventional electrodes (e.g., BDD, graphite).
- Decolorization and Mineralization: Achieved 91.82% decolorization in 180 minutes and a high 96% Chemical Oxygen Demand (COD) removal after 360 minutes of treatment.
- Kinetic Performance: The degradation followed pseudo-first-order kinetics. The rate constant (k) increased significantly from 0.00261 min-1 to 0.0141 min-1 as the current density increased from 100 to 400 mA.cm-2.
- Optimal Conditions: Best performance was achieved under acidic conditions (pH=3), which favors the generation of highly oxidative hydroxyl radicals (OH).
- Electrolyte Effect: Potassium chloride (KCl) supporting electrolyte outperformed Na2SO4, enhancing degradation (92.66% vs. 82.23% removal) due to the formation of reactive chlorine species (Cl2, HOCl).
- Material Advantage: Gold was selected for its exceptional corrosion resistance and high electrical conductivity, ensuring long-term operational stability in harsh, oxidizing environments.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Working Electrode Material | Porous Gold | N/A | Anode in the electrochemical cell |
| Target Contaminant | Reactive Blue 203 (RB203) | N/A | Azo dye (C28H29N5O21S6-4Na) |
| Initial Dye Concentration | 40 | mg/L | Standard experimental concentration |
| Optimal Current Density (i) | 400 | mA.cm-2 | Achieved maximum decolorization rate |
| Maximum Decolorization | 91.82 | % | At 400 mA.cm-2, 180 min |
| Maximum COD Removal | 96 | % | After 360 min treatment |
| Optimal Initial pH | 3 | N/A | Favors OH radical formation |
| Kinetic Rate Constant (k) at 400 mA.cm-2 | 0.0141 | min-1 | Highest k observed for current density variation |
| Kinetic Rate Constant (k) at pH 3 | 0.01305 | min-1 | Highest k observed for pH variation |
| Optimal Electrolyte | KCl (0.2 M) | N/A | Promotes indirect oxidation via Cl2/HOCl |
| Electrolysis Time (Decolorization) | 180 | min | Standard duration for kinetic studies |
| Electrolysis Time (COD) | 360 | min | Duration for maximum mineralization |
| Reaction Kinetics | Pseudo-first-order | N/A | Confirmed by R2 values up to 0.97027 |
Key Methodologies
Section titled âKey MethodologiesâThe electrochemical oxidation experiments were conducted using a controlled three-electrode system in a non-compartmentalized reactor.
- Electrochemical Setup: A PGZ 301 potentiostat was used to control the applied current. The system utilized a Porous Gold working electrode, a Platinum (Pt) counter electrode, and a Saturated Calomel Electrode (SCE) as the reference.
- Solution Preparation: Experiments used RB203 at 40 mg/L (or 0.1 mM) supported by 0.2 M electrolytes (Na2SO4 or KCl). The solution volume was 50 mL, maintained at 20 °C ambient temperature with magnetic stirring.
- Current Density Variation: The effect of current density was tested across a range of 100, 200, 300, and 400 mA.cm-2 to determine the optimal rate of OH radical generation.
- pH Optimization: Initial pH was adjusted using H2SO4 or NaOH to test values ranging from 3 to 11, confirming that acidic conditions accelerate degradation kinetics.
- Electrolyte Comparison: The performance of KCl versus Na2SO4 was evaluated to quantify the impact of indirect oxidation mechanisms (i.e., generation of reactive chlorine species from KCl).
- Analytical Monitoring: Decolorization efficiency was measured by monitoring absorbance at the maximum visible wavelength (605 nm) using a UV-Vis spectrophotometer. Mineralization was quantified via titrimetric Chemical Oxygen Demand (COD) analysis.
- Kinetic Modeling: Degradation data (ln(C0/C) vs. time) were fitted to a pseudo-first-order model to determine rate constants (k) and coefficients of determination (R2).
Commercial Applications
Section titled âCommercial ApplicationsâThis technology, leveraging the stability and high activity of porous gold electrodes in EAOP, is highly relevant for industries requiring robust and efficient water purification systems.
- Textile and Dye Manufacturing: Direct application for treating highly concentrated, colored wastewater streams, offering a compact and energy-efficient solution for meeting stringent discharge regulations.
- Industrial Wastewater Treatment: Applicable to the degradation of complex, non-biodegradable organic pollutants (e.g., pharmaceuticals, pesticides, and other specialty chemicals) where conventional biological or physical methods fail.
- Electrocatalytic Reactor Design: The porous gold material can be integrated into modular electrochemical reactors for continuous flow-through treatment systems, benefiting from goldâs superior corrosion resistance and long lifespan.
- Water Reclamation and Reuse: Provides a high-mineralization step (96% COD removal) necessary for closing the water loop in industrial facilities, supporting sustainable manufacturing practices.
- Advanced Sensor and Electrode Manufacturing: The findings on goldâs electrocatalytic behavior in acidic and oxidizing environments inform the design of durable electrodes for various electrochemical processes beyond wastewater treatment.
View Original Abstract
MAX 250 words This study evaluates the efficiency of anodic oxidation processes for the degradation of the azo dye Reactive Blue 203 (RB203) using a gold electrode in an compartmented electrochemical cell. Unlike most studies that rely on conventional electrodes such as BDD or graphite, this work explores the use of a porous gold electrodeâan uncommon yet promising material in dye degradationâhighlighting its high electrocatalytic activity and exceptional chemical stability. Experiments explored the effects of current density, initial pH and type of supporting electrolyte. The gold electrode performed remarkably well, achieving a 91.82% decolorization rate and 96% Chemical Oxygen Demand (COD) removal after 360 minutes of treatment. Best performance was observed under acidic conditions (pH = 3), where the formation of hydroxyl radicals (âOH) is favored. The use of KCl as a supporting electrolyte improved degradation compared to NaâSOâ, thanks to better ionic conductivity and the generation of reactive species such as Clâ and HOCl. Kinetic analysis revealed that the reaction follows a pseudo-first-order model, with rate constants increasing from 0.00261 min-š to 0.0141 min-š as the current density increases from 100 to 400 mA.cm-². These results confirm that anodic oxidation, with the gold electrode, is an effective and sustainable method for treating textile wastewater