Response Surface Modeling for COD Removal in Electroplating Effluent Using Sacrificial Electrodes by Electro Fenton Process - Optimization and Analysis
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-09-01 |
| Journal | Nature Environment and Pollution Technology |
| Authors | V. Nandhini, S. Dhanakumar, M. Durga |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis study successfully optimized the Electro-Fenton (EF) process using sacrificial stainless steel electrodes for the efficient removal of Chemical Oxygen Demand (COD) from electroplating wastewater.
- Core Value Proposition: The EF process provides a sustainable and cost-effective method for degrading persistent, complex organic pollutants in industrial effluent, achieving mineralization rather than simple separation.
- Optimization Method: Response Surface Methodology (RSM) coupled with Box-Behnken Design (BBD) was employed to model and optimize critical operating parameters (pH, Fe2+ concentration, and H2O2 concentration).
- Peak Performance: A maximum COD removal efficiency of 80.45% was achieved under optimal conditions.
- Optimal Parameters: The ideal operating regime was determined to be pH 2, 0.005 M Fe2+, 0.5 M H2O2, and a constant stirring speed of 450 RPM.
- Kinetic Modeling: The pollutant degradation rate accurately followed pseudo-first-order kinetics (R2 = 0.9068), confirming rapid reaction progression under optimized conditions.
- Material Selection: Sacrificial stainless steel was chosen for its affordability and ability to generate the necessary Fe2+ catalyst in situ, reducing external reagent consumption.
- Model Reliability: The quadratic regression model demonstrated high precision (R2 = 0.9585) and adequacy (AP = 11.9342), ensuring reliable prediction of treatment outcomes.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Initial COD Concentration | 1080 | mg.L-1 | Raw Electroplating Effluent |
| Maximum COD Removal | 80.45 | % | Achieved at optimal conditions |
| Optimal Initial pH | 2 | - | Favors hydroxyl radical (â˘OH) generation |
| Optimal Ferrous Ion (Fe2+) | 0.005 | M | Catalyst concentration |
| Optimal Hydrogen Peroxide (H2O2) | 0.5 | M | Oxidant concentration |
| Stirring Speed | 450 | RPM | Maintained constant during electrolysis |
| Electrode Material | Stainless Steel | - | Sacrificial anode/cathode |
| Inter-Electrode Gap | 1 | cm | Reactor configuration |
| Kinetic Model Fit | Pseudo-First-Order | - | Best fit for degradation (R2 = 0.9068) |
| First Order Rate Constant (k1) | 0.027 | min-1 | Rate of pollutant reduction |
| Regression Model Precision (R2) | 0.9585 | - | Coefficient of determination for quadratic model |
| Model Adequacy (AP) | 11.9342 | - | Signal-to-noise ratio (AP > 4 required) |
Key Methodologies
Section titled âKey Methodologiesâ- Effluent Characterization: Electroplating wastewater was analyzed (Initial pH 4.8, COD 1080 mg.L-1, Electrical Conductivity 2.2 mS.cm-1) and stored at 4°C prior to treatment.
- Electrochemical Setup: A glass reactor containing 0.5 L of effluent was equipped with sacrificial stainless steel electrodes separated by 1 cm and connected to a precision DC power supply.
- Electrolyte and pH Control: Sodium sulfate (Na2SO4) was added to increase conductivity. The pH was adjusted using HCl to the target range (2-5) to ensure H2O2 stability and optimal Fenton reaction kinetics.
- Optimization Design (BBD-RSM): The Box-Behnken Design was used to define fifteen experimental runs, varying pH, Fe2+ concentration, and H2O2 concentration across three levels (low, medium, high).
- Reaction Execution: Each run was performed under constant stirring (450 RPM). The EF process generates H2O2 electrochemically at the cathode and utilizes the Fe2+ sacrificed from the anode to produce highly reactive hydroxyl radicals (â˘OH).
- Performance Measurement: Following treatment, the wastewater was filtered, and the final COD concentration was measured (APHA 2017). Removal efficiency was calculated based on the initial and final COD values.
- Kinetic Analysis: The degradation data was fitted to zero, first, and second-order kinetic models to determine the rate-limiting step, confirming a pseudo-first-order mechanism.
Commercial Applications
Section titled âCommercial ApplicationsâThe optimized Electro-Fenton process using sacrificial stainless steel electrodes is highly relevant for industries requiring robust and cost-effective treatment of complex liquid waste streams.
- Electroplating and Metal Finishing Industry: Direct application for detoxification of effluent containing high concentrations of heavy metals (e.g., zinc, copper, nickel) and persistent organic compounds (high COD).
- Advanced Oxidation Processes (AOPs) Integration: Provides a scalable alternative to traditional Fenton processes by generating the necessary reagents (Fe2+ and H2O2) in situ, minimizing reagent handling and storage risks.
- Sludge Minimization Technology: By achieving mineralization (degradation) of organic pollutants rather than just phase separation (like adsorption or RO), the process reduces the volume and toxicity of secondary iron sludge generated, lowering disposal costs.
- Sustainable Industrial Water Management: Offers a pathway for industries to meet stringent environmental discharge regulations by efficiently breaking down refractory pollutants that resist conventional biological or physical treatments.
View Original Abstract
The effluent produced by the electroplating industry contains hazardous and toxic chemicals that pose a threat to living organisms and ecosystems. Consequently, it is essential to employ advanced treatment technologies to remove the toxicants from the wastewater. Over the past two decades, the concept of Electro Fenton has been developed and demonstrated as an effective method for significantly alleviating pollutants in wastewater, making it a promising solution for treating wastewater. In the present investigation, the efficiency of the Electro Fenton (EF) process in removing Chemical oxygen demand (COD) from electroplating wastewater using stainless steel as the sacrificial electrode was examined. The influence of various operating parameters, including pH, hydrogen peroxide concentration, reaction time, and Fe2+ concentration, was investigated with the help of Box-Behnken design (BDD) in Response surface methodology (RSM). Notably, EF treatability studies demonstrated that optimal conditions of pH 2, Fe2+ concentration of 0.005M, H2O2 concentration of 0.5M, and RPM of 450 resulted in more than 75% COD removal. Hence, the sacrificial electrodes can be effective in removing COD from the wastewater.