Removal of Orange G dye from water by heterogeneous electro Fenton-based processes using Ti4O7 anode and different iron-based catalysts
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-04-01 |
| Journal | Emergent Materials |
| Authors | Fatima Ezzahra Titchou, Rachid AıÌt Akbour, Mohamed Hamdani, Mehmet A. Oturan |
| Citations | 1 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis study validates the use of heterogeneous electro-Fenton (HEF) and photoelectro-Fenton (HPEF) processes, utilizing a cost-effective Ti4O7 anode and recycled stainless steel (SS) sludge catalyst, for highly efficient Orange G (OG) dye removal.
- Sustainable Catalyst Valorization: SS sludge, a waste product from electrocoagulation, was identified as the most effective heterogeneous catalyst, achieving 82.33% TOC removal in the HPEF process.
- Cost-Effective Electrode Alternative: The Ti4O7/Carbon Felt (CF) cell configuration demonstrated comparable mineralization efficiency (82.33% TOC removal) to the traditional, expensive Boron Doped Diamond (BDD)/CF cell (84.25% TOC removal).
- Superior Energy Metrics: The HPEF-Ti4O7/CF system achieved significantly lower energy consumption (EC) (0.32 kWh (kg TOC)-1) compared to the AO-BDD/CF system (0.44 kWh (kg TOC)-1).
- Process Optimization: Optimal conditions were established at pH 3.0, 1.67 mA cm-2 current density, and 10 mg SS sludge loading, maximizing TOC removal while maintaining high Mineralization Current Efficiency (MCE).
- Catalyst Stability: The SS sludge catalyst exhibited excellent reusability, maintaining stable activity even after five consecutive cycles, confirming its potential for long-term industrial application.
- Synergistic Effect: HPEF (using UV-A irradiation) significantly enhanced degradation and mineralization rates compared to HEF alone, attributed to enhanced hydroxyl radical generation and catalyst regeneration.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Target Pollutant | Orange G (OG) | Dye | C16H10N2Na2O7S2 (MW=452.38 g mol-1) |
| Optimal Current Density (HPEF) | 1.67 | mA cm-2 | Used for best TOC/EC trade-off |
| Optimal pH | 3.00 (±0.30) | - | Maintained for maximum efficiency |
| Supporting Electrolyte | 50 | mM | Na2SO4 |
| Optimal SS Sludge Dosage | 10 | mg | Catalyst load for 230 mL solution |
| HPEF TOC Removal (SS Sludge, 5h) | 82.33 | % | Ti4O7/CF cell, 1.67 mA cm-2 |
| AO TOC Removal (BDD, 5h) | 84.25 | % | BDD/CF cell, 1.67 mA cm-2 (Benchmark) |
| HPEF Energy Consumption (EC) | 0.32 | kWh (kg TOC)-1 | Ti4O7/CF cell (lower than BDD benchmark) |
| AO Energy Consumption (EC) | 0.44 | kWh (kg TOC)-1 | BDD/CF cell |
| HPEF MCE (5h) | 11.54 | % | Ti4O7/CF cell |
| AO MCE (5h) | 14.98 | % | BDD/CF cell |
| SS Sludge Composition (Key Oxides) | Magnetite, Trevorite, Chromite | - | Fe3O4, NiFe2O4, FeCr2O4 (Confirmed by XRD) |
| UV Source Type | UV LED 400 Solo lamp | - | UV-A spectrum, peak wavelength ~400 nm |
| UV Power Rating | 1.50 | W | Low power consumption |
Key Methodologies
Section titled âKey MethodologiesâThe electrochemical advanced oxidation processes (EAOPs) were conducted in an undivided batch electrolytic cell (230 mL volume) under galvanostatic control.
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Electrode Configuration:
- Anode: Magnéli phase Ti4O7 thin film (4 cm x 6 cm x 0.20 cm) on a Ti substrate.
- Cathode: Carbon-felt (CF) (64 cm2 area) for electrochemical H2O2 generation.
- Note: BDD anode (4 cm x 10 cm x 0.20 cm) was used for comparative AO benchmarking.
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Catalyst Preparation (SS Sludge):
- Sludge was generated via electrocoagulation (SS electrodes, 20 mA cm-2, 15 min, 0.1 M NaCl).
- Sludge was dried, washed to remove excess salts, and thermally treated at 300 °C to eliminate adsorbed organic matter.
- Final particle size was milled and sieved to be less than 80 ”m.
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Process Operation (HEF/HPEF):
- Solutions were saturated with oxygen (compressed air, 1.5 L min-1) for 10 minutes prior to and continuously throughout electrolysis.
- The optimal current density was fixed at 1.67 mA cm-2 for efficiency comparison.
- HPEF Specifics: Continuous UV-A irradiation was applied using a 1.50 W LED lamp positioned 4 cm above the reaction medium.
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Catalyst Screening:
- Four heterogeneous catalysts were tested: SS sludge, Iron sludge, Pyrite (natural mineral), and Titaniferous sand (natural mineral).
- SS sludge was selected as the optimal catalyst based on superior TOC removal, MCE, and EC metrics.
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Performance Assessment:
- Mineralization: Monitored via Total Organic Carbon (TOC) analysis using a TOC-L SHIMADZU analyzer (thermal catalytic oxidation at 680 °C).
- Discoloration: Monitored via UV-Vis spectrophotometry at λmax=478 nm.
- Efficiency Metrics: MCE (%) and EC (kWh (kg TOC)-1) were calculated based on standard electrochemical equations.
Commercial Applications
Section titled âCommercial ApplicationsâThe findings support the deployment of sustainable and energy-efficient electrochemical systems in several high-value engineering sectors:
- Textile and Dye Manufacturing: Direct application for treating highly colored wastewater containing persistent azo dyes like Orange G, achieving high discoloration and mineralization rates.
- Pharmaceutical Wastewater Treatment: EAOPs are highly effective against recalcitrant organic contaminants (RECs). The stable, reusable SS sludge catalyst offers a low-cost solution for treating complex pharmaceutical effluents.
- Sustainable Water Management: Implementation of Ti4O7 anodes as a durable, low-cost, and high-performance alternative to expensive BDD electrodes in large-scale AOP reactors.
- Waste Valorization and Circular Economy: Utilizing electrocoagulation sludge (a common industrial waste stream) as a functional, high-activity heterogeneous catalyst, reducing disposal costs and material sourcing needs.
- Electrochemical Reactor Design: Optimization data (current density, catalyst loading, pH) provides critical parameters for scaling up HEF and HPEF reactors for industrial flow systems.
View Original Abstract
Abstract Removal of Orange G (OG) dye from water by anodic oxidation (AO), heterogeneous electro Fenton (HEF), and heterogeneous photoelectro-Fenton (HPEF) processes was systematically investigated under different operating conditions. Four distinct heterogeneous catalysts were used in this study: titaniferous sand, pyrite, and sludge derived from electrocoagulation using stainless steel (SS sludge) or iron electrodes (iron sludge); within an electrolytic cell equipped with a Ti 4 O 7 anode and carbon-felt (CF) cathode, a cost-effective configuration for advanced oxidation processes. The optimal operating conditions were chosen based on comparison of total organic carbon (TOC) removal efficiency, mineralization current efficiency (MCE (%)), and energy consumption (EC). A key highlight is the comparison of Ti 4 O 7 /CF and BDD/CF cells, demonstrating that the former cell offers comparable degradation efficiency with significantly improved MCE and low EC values, underscoring its potential as a cost-efficient alternative to traditional AO systems. The used iron-based materials were characterized using SEM-EDS and X-ray diffraction analyses. Besides, reusability runs were performed to demonstrate the sustainability of the most effective catalyst, the SS sludge. Results showed that the most effective treatment of OG solution was achieved using SS sludge, with a stable activity even after five cycles. The HPEF process with Ti 4 O 7 /CF cell exhibited comparable degradation efficiency as the AO process with the BDD/CF cell. Specifically, both the AO process using BDD/CF cell and HPEF with Ti 4 O 7 /CF cell achieved similar mineralization efficiencies, i.e., 84.25% and 82.33%, respectively, while the latter exhibited better MCE and EC values. These findings establish the HPEF process using Ti 4 O 7 /CF cell as an innovative, sustainable, and energy-efficient alternative for dye removal, advancing the application of heterogeneous catalysts in wastewater treatment.