Electrochemical degradation of surfactants in domestic wastewater using a DiaClean® cell equipped with a boron-doped diamond electrode
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2023-04-25 |
| Journal | Frontiers in Chemistry |
| Authors | Dayana G. Cisneros-León, Patricio J. Espinoza-Montero, Diego Bolaños-Méndez, Jocelyne Álvarez-Paguay, Lenys Fernández |
| Institutions | National Polytechnic School, Pontificia Universidad Católica del Ecuador |
| Citations | 9 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This analysis focuses on the application of Advanced Electro-Oxidation (AEO) using a Boron-Doped Diamond (BDD) electrode within a commercial DiaClean® cell for the remediation of real domestic wastewater containing high loads of surfactants.
- Core Technology: The system utilizes a DiaClean® cell with a BDD anode and a T304 Stainless Steel (SS) cathode in a galvanostatic recirculation setup, demonstrating excellent mass transfer and current distribution.
- Optimal Performance: The best results were achieved at a low recirculation flow rate (1.5 L min-1) and a moderate current density (14 mA cm-2) over 7 hours of electrolysis.
- Key Removal Metrics: Under optimal conditions, the process achieved 64.7% removal of surfactants, 48.7% Chemical Oxygen Demand (COD) removal, and 44.9% Total Organic Carbon (TOC) mineralization.
- Kinetic Behavior: Surfactant degradation followed zero-order kinetics (k = 0.0011 min-1), while COD and TOC mineralization followed pseudo-first-order kinetics (k = 0.028 min-1 and k = 0.0076 min-1, respectively).
- Economic Viability: The system exhibited low energy consumption (2.59 kWh m-3) and a calculated operating cost of 1.40 USD m-3, positioning AEO as a promising, cost-effective technology, potentially powered by solar energy.
- Toxicity Concern: Ecotoxicity tests showed that the AEO-treated wastewater was highly toxic to Chlorella sp. microalgae (cellular density dropped to 0 × 104 cells ml-1), likely due to the formation of highly oxidizing reactive species (HORS) intermediates.
- Compliance: Despite the toxicity, the final effluent quality (COD, pH, sulfates, nitrates, chlorides) complied with Ecuadorian environmental regulations for discharge into freshwater bodies.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Anode Material | Boron-Doped Diamond (BDD) | N/A | DiaClean® cell |
| Cathode Material | T304 Stainless Steel (SS) | N/A | DiaClean® cell |
| Electrode Surface Area | 70 | cm2 | Both anode and cathode |
| BDD Thickness | 1-10 | µm | Deposited on silicon |
| BDD Resistance | 0.1 | Ω cm | N/A |
| Optimal Current Density (j) | 14.0 | mA cm-2 | Max removal efficiency |
| Optimal Flow Rate (Q) | 1.5 | L min-1 | Recirculation system |
| Electrolysis Time | 7 | h | Total treatment duration |
| Initial TOC Concentration (Co) | 103 | mg L-1 | Domestic wastewater |
| TOC Mineralization (Optimal) | 44.9 | % | Removal percentage |
| Surfactant Removal (Optimal) | 64.7 | % | Removal percentage |
| COD Removal (Optimal) | 48.7 | % | Removal percentage |
| Surfactant Degradation Kinetics | Zero-order (k = 0.0011) | min-1 | At 1.5 L min-1 |
| COD Removal Kinetics | Pseudo-first-order (k = 0.028) | min-1 | At 1.5 L min-1 |
| Energy Consumption (EC) | 2.59 | kWh m-3 | DiaClean cell only |
| Operating Cost | 1.40 | USD m-3 | Based on 0.063 USD kWh-1 |
| Final pH (Optimal) | 9.38 | N/A | Compliant with regulations (5-9) |
| Final Temperature (Optimal) | 24.8 | °C | Compliant with regulations (<35 °C) |
Key Methodologies
Section titled “Key Methodologies”The electrochemical degradation was performed under galvanostatic control using a commercial DiaClean® cell coupled to a recirculation system.
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System Configuration:
- A 6 L volume of real domestic wastewater was treated in a recirculation loop using a peristaltic pump.
- The DiaClean® cell housed a BDD disk anode and a T304 SS disk cathode, both with 70 cm2 surface area.
- The system was monitored using a galvanostat (GW INSTEK SPS-3610) and a multimeter.
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Electrode Preparation:
- Prior to each 7-hour experiment, electrodes were cleaned using a 0.1 M H2SO4 solution with a 2 A current applied for 15 minutes to remove surface impurities.
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Flow Rate Optimization (Fixed Current Density):
- The effect of recirculation flow was tested at 1.5, 4.0, and 7.0 L min-1, maintaining a constant current density of 14 mA cm-2.
- The lowest flow rate (1.5 L min-1) was selected as optimal due to increased residence time and better interaction with BDD-generated oxidizing species.
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Current Density Optimization (Fixed Flow Rate):
- Current density (j) was varied across 7, 14, 20, 30, 40, and 50 mA cm-2, maintaining the optimal flow rate of 1.5 L min-1.
- 14 mA cm-2 was identified as optimal, balancing high removal efficiency with minimized energy loss due to excessive oxygen evolution and foam formation observed at higher currents.
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Analytical Monitoring:
- Degradation was tracked by measuring surfactants, COD, and TOC hourly.
- Water quality parameters (pH, conductivity, temperature, sulfates, nitrates, phosphates, chlorides) were also monitored.
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Ecotoxicity Testing:
- Chlorella sp. growth was assessed over 30 days in untreated wastewater, 3-hour treated wastewater, and 7-hour treated wastewater.
- Cell density was counted every 3 days using Neubauer plates and an optical microscope.
Commercial Applications
Section titled “Commercial Applications”The use of BDD electrodes in AEO systems, particularly within efficient commercial cells like DiaClean®, is highly relevant for treating complex, stable organic matrices in various industrial and municipal settings.
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Municipal Wastewater Treatment:
- Post-conventional treatment polishing step to remove persistent organic pollutants (POPs) that bypass biological processes, such as surfactants, pesticides, and pharmaceuticals.
- Ensuring effluent compliance with strict discharge regulations, especially concerning COD and TOC.
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Industrial Effluent Remediation:
- Treatment of highly concentrated industrial streams (e.g., textile, pharmaceutical, and chemical manufacturing) where stable organic molecules require complete mineralization.
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Water Reuse and Recycling:
- AEO serves as a robust technology for generating high-quality water for industrial or agricultural reuse by effectively destroying endocrine disruptors and toxic intermediates.
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High-Stability Contaminant Destruction:
- Specific application for degrading molecules resistant to conventional methods, leveraging the high oxidation potential of BDD-generated hydroxyl radicals (OH) and other HORS (e.g., Cl2, S2O82-, P2O84-).
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BDD Electrode Manufacturing (6ccvd.com Relevance):
- The success of this AEO process relies entirely on the high electrochemical stability and wide potential window of the BDD anode material, confirming the demand for high-quality, large-area BDD films for commercial reactor deployment.
View Original Abstract
Treating domestic wastewater has become more and more complicated due to the high content of different types of detergents. In this context, advanced electro-oxidation (AEO) has become a powerful tool for complex wastewater remediation. The electrochemical degradation of surfactants present in domestic wastewater was carried out using a DiaClean ® cell in a recirculation system equipped with boron-doped diamond (BDD) as the anode and stainless steel as the cathode. The effect of recirculation flow (1.5, 4.0 and 7.0 L min −1 ) and the applied current density (j = 7, 14, 20, 30, 40, and 50 mA cm −2 ) was studied. The degradation was followed by the concentration of surfactants, chemical oxygen demand (COD), and turbidity. pH value, conductivity, temperature, sulfates, nitrates, phosphates, and chlorides were also evaluated. Toxicity assays were studied through evaluating Chlorella sp . performance at 0, 3, and 7 h of treatment. Finally, the mineralization was followed by total organic carbon (TOC) under optimal operating conditions. The results showed that applying j = 14 mA cm −2 and a flow rate of 1.5 L min −1 during 7 h of electrolysis were the best conditions for the efficient mineralization of wastewater, achieving the removal of 64.7% of surfactants, 48.7% of COD, 24.9% of turbidity, and 44.9% of mineralization analyzed by the removal of TOC. The toxicity assays showed that Chlorella microalgae were unable to grow in AEO-treated wastewater (cellular density: 0 × 10 4 cells ml −1 after 3- and 7-h treatments). Finally, the energy consumption was analyzed, and the operating cost of 1.40 USD m −3 was calculated. Therefore, this technology allows for the degradation of complex and stable molecules such as surfactants in real and complex wastewater, if toxicity is not taken into account.
Tech Support
Section titled “Tech Support”Original Source
Section titled “Original Source”References
Section titled “References”- 2017 - Electrochemical degradation of nonylphenol ethoxylate-7 (NP7EO) using a DiaClean® cell equipped with boron-doped diamond electrodes (BDD) [Crossref]
- 2018 - Standard Methodds for The Examination Of Water and Wastewater
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- 2019 - Boron-doped diamond for hydroxyl radical and sulfate radical anion electrogeneration, transformation, and voltage-free sustainable oxidation [Crossref]
- 2005 - Electrochemical synthesis of peroxodiphosphate using boron-doped diamond anodes [Crossref]
- 2016 - Use of DiaCell modules for the electro-disinfection of secondary-treated wastewater with diamond anodes [Crossref]
- 2014 - Microbial characterization and degradation of linear alkylbenzene sulfonate in an anaerobic reactor treating wastewater containing soap powder [Crossref]