The Removal of Organic Pollutants and Ammonia Nitrogen from High-Salt Wastewater by the Electro-Chlorination Process and Its Mechanism
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-12-18 |
| Journal | Separations |
| Authors | Yujun Zhou, Ting Hou, Bo Zhou |
| Institutions | Nanjing Agricultural University, Nanjing University of Science and Technology |
| Citations | 3 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Electro-Chlorination (E-Cl) for High-Salt Wastewater
Section titled âTechnical Documentation & Analysis: Electro-Chlorination (E-Cl) for High-Salt WastewaterâExecutive Summary
Section titled âExecutive SummaryâThis review highlights the critical role of advanced electrode materials, particularly Boron-Doped Diamond (BDD), in the highly efficient Electro-Chlorination (E-Cl) process for treating high-salt wastewater.
- Core Technology: E-Cl is a green, high-efficiency electrochemical advanced oxidation process achieving deep mineralization of pollutants (organic compounds and ammonia nitrogen).
- Mechanism: Pollutant removal is driven primarily by indirect oxidation using in situ generated Reactive Chlorine Species (RCS) (e.g., HClO, ClO¯) and highly reactive chlorine radicals (·Cl) produced at the anode.
- Material Advantage: Boron-Doped Diamond (BDD) electrodes are identified as superior non-active anodes, offering high oxygen evolution overpotential (2.54 V - 2.66 V vs. Ag/AgCl) and exceptional electrochemical stability, crucial for high-salinity environments.
- Application Focus: E-Cl is highly effective for challenging industrial effluents, including dyeing, petrochemical, and antibiotic wastewater, leveraging the high ClÂŻ concentration as the necessary electrolyte.
- Reactor Design: Flow-through electrode reactors are the most promising configuration, significantly enhancing mass transfer and electron transfer efficiency compared to traditional flow-by systems.
- Performance Metrics: Case studies demonstrate 100% removal efficiency for complex contaminants like Levofloxacin and Cefadroxil under optimized current densities (e.g., 18-39.6 mA/cm2).
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points extracted from the review summarize the key electrochemical properties and performance metrics relevant to E-Cl systems.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Hydroxyl Radical (·OH) Redox Potential | 2.8 | V | Non-selective strong oxidant |
| Chlorine Radical (·Cl) Redox Potential | 2.4 | V | High electrophilicity, higher selectivity |
| Hydroxyl Radical (·OH) Half-Life | 10-9 | s | Extremely short existence time |
| Chlorine Radical (·Cl) Half-Life | 3 x 10-6 | s | Longer than ·OH |
| RCS Half-Life (e.g., HClO, ClOÂŻ) | 9 - 12 | h | Prolonged contact time with pollutants |
| BDD Oxygen Overpotential (Si/BDD) | 2.54 | V | vs. Ag/AgCl, Non-active anode |
| BDD Energy Consumption (Ti/BDD) | 1.00 | kWh/g | vs. Ag/AgCl reference |
| Levofloxacin Removal Efficiency (BDD) | 100 | % | 100 mg/L initial concentration, 30 min |
| Cefadroxil (CFDX) Removal Efficiency (DSA) | 100 | % | 55 ”mol/L initial concentration, 15 min |
| Tetracycline Removal Efficiency (Ti/IrO2-RuO2) | 100 | % | 50 mg/L initial concentration, 30 min |
Key Methodologies
Section titled âKey MethodologiesâThe E-Cl process relies on precise material selection and controlled electrochemical parameters to maximize the generation of active chlorine species.
- Electrochemical Oxidation (E-Cl): Utilizing ClÂŻ-containing wastewater as the electrolyte, electricity is applied to generate strong oxidants in situ.
- Anode Material Selection: Anodes are categorized by oxygen evolution overpotential:
- Active Anodes (e.g., DSA, Pt): Lower chlorine evolution overpotential, prone to Oxygen Evolution Reactions (OERs).
- Non-Active Anodes (e.g., BDD): High oxygen evolution overpotential, favoring the production of chlorine radicals and RCS.
- Pollutant Degradation: Achieved primarily via indirect oxidation by in situ generated Reactive Chlorine Species (RCS) (HClO, ClO¯, Cl2) and chlorine radicals (·Cl, ·ClO).
- Reactor Configuration: Optimization favors flow-through electrode reactors, which use porous electrode materials to create a layered, three-dimensional structure, significantly improving mass and electron transfer efficiency.
- Operating Parameters: Critical factors influencing efficiency include applied current density (ranging from 3 mA/cm2 to 800 A/m2), voltage, electrolyte (ClÂŻ) concentration, and initial pH value.
- Active Species Detection: Qualitative and quantitative verification of radicals and RCS using advanced techniques:
- Electron Paramagnetic Resonance (EPR) with scavengers (e.g., DMPO).
- Spectrophotometry using chromogenic agents (e.g., N, N-diethyl-1,4-phenylenediamine sulfate (DPD)).
- Ion Chromatography (IC) for detecting species like ClO2ÂŻ, ClO3ÂŻ, and ClO4ÂŻ.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD specializes in high-quality MPCVD diamond materials, providing the foundational components necessary to advance and scale the high-performance E-Cl systems described in this research. The superior stability and wide electrochemical window of diamond are essential for the next generation of wastewater treatment anodes.
Applicable Materials
Section titled âApplicable MaterialsâThe research explicitly identifies Boron-Doped Diamond (BDD) as a key material for high-efficiency E-Cl anodes. 6CCVD offers BDD tailored for electrochemical applications:
| Material | Description | Application Relevance to E-Cl |
|---|---|---|
| Heavy Boron-Doped PCD | Polycrystalline Diamond (PCD) wafers/plates with high boron concentration for maximum conductivity. | Ideal for non-active anodes requiring high oxygen evolution overpotential and chemical inertness in highly corrosive, high-salt environments. |
| BDD Thin Films on Substrates | Custom BDD films deposited onto conductive substrates (e.g., Si, Ti, W) for cost-effective, large-area electrode manufacturing. | Enables the fabrication of complex, multilayer electrode structures (e.g., Ti/BDD) optimized for flow-through reactors. |
| Optical Grade SCD/PCD | High-purity Single Crystal (SCD) or Polycrystalline Diamond (PCD) substrates. | Used as robust, inert structural components or dielectric separators in advanced flow-through reactor designs, especially those combining E-Cl with UV irradiation (Photo-E-Cl). |
Customization Potential for E-Cl Systems
Section titled âCustomization Potential for E-Cl SystemsâTo move E-Cl technology from the lab scale to industrial application, custom material engineering is indispensable. 6CCVDâs in-house capabilities directly address the challenges of developing stable, efficient, and low-cost electrode materials:
| Capability | Technical Specification | Relevance to E-Cl Scale-Up |
|---|---|---|
| Custom Dimensions | Plates/wafers up to 125mm (PCD). Substrates up to 10mm thickness. | Essential for scaling up flow-through reactors and achieving mass production of large-area electrodes. |
| Surface Engineering | Polishing down to Ra < 5nm (PCD) and Ra < 1nm (SCD). | Ensures optimal surface morphology for uniform BDD deposition, maximizing active sites for chlorine radical generation. |
| Advanced Metalization | Internal capability for Au, Pt, Pd, Ti, W, Cu deposition. | Critical for creating robust, low-resistance electrical contacts and integrating BDD films into complex multilayer anodes (e.g., Ti/RuO2-IrO2/BDD structures). |
| Thickness Control | SCD/PCD films from 0.1”m to 500”m. | Allows precise control over BDD film thickness to balance performance, cost, and longevity in high-current density operations. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team offers authoritative professional support for material selection and optimization in electrochemical advanced oxidation processes. We assist engineers and scientists in:
- Anode Recipe Optimization: Tailoring boron doping levels and film thickness to achieve specific oxygen evolution overpotentials required for selective chlorine radical generation in high-salinity wastewater projects.
- Reactor Integration: Providing consultation on integrating custom BDD plates into flow-through reactor designs to maximize mass transfer efficiency and minimize energy consumption.
- Corrosion Mitigation: Selecting the most stable diamond material and metalization layers to withstand the highly corrosive environment generated by chlorine radicals and high current densities.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Electro-chlorination (E-Cl) is an emerging and promising electrochemical advanced oxidation technology for wastewater treatment with the advantages of high efficiency, deep mineralization, a green process, and easy operation. It was found that the mechanism of pollutant removal by electro-chlorination mainly involves an indirect oxidation process, in which pollutant removal is mainly driven by the intermediate active species, especially RCS and chlorine radicals, with a strong oxidization ability produced at the anodes. In this work, we summarized the principles and pathways of the removal/degradation of pollutants (organic pollutants and ammonia nitrogen) by E-Cl and the major affecting factors including the applied current density, voltage, electrolyte concentration, initial pH value, etc. In the E-Cl system, the DSA and BDD electrodes were the most widely used electrode materials. The flow-through electrode reactor was considered to be the most promising reactor since it had a high porosity and large pore size, which could effectively improve the mass transfer efficiency and electron transfer efficiency of the reaction. Of the many detection methods for chlorine radicals and RCS, electron paramagnetic resonance (EPR) and spectrophotometry with N, N-diethyl-1,4-phenylenediamine sulfate (DPD) as the chromogenic agent were the two most widely used methods. Overall, the E-Cl process had excellent performance and prospects in treating salt-containing wastewater.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
Section titled âReferencesâ- 2021 - Recent developments in physical, biological, chemical, and hybrid treatment techniques for removing emerging contaminants from wastewater [Crossref]
- 2023 - Plant tannin foam anchored iron nanoparticles: Efficient and recyclable degradation of tetracycline antibiotics under high salt conditions [Crossref]
- 2024 - Review on ultrasonic technology enhanced biological treatment of wastewater [Crossref]
- 2015 - Challenges and Opportunities for electrochemical processes as next-generation technologies for the treatment of contaminated water [Crossref]
- 2009 - Electro-Fenton process and related electrochemical technologies based on Fentonâs reaction chemistry [Crossref]
- 2008 - The Synergistic Influences of OH- concentration and electrolyte conductivity on the redox behavior of Ni(OH)2/NiOOH [Crossref]
- 2021 - Current progress in electrochemical anodic-oxidation of pharmaceuticals: Mechanisms, influencing factors [Crossref]
- 2024 - Electrogenerated singlet oxygen and reactive chlorine species enhancing volatile fatty acids production from co-fermentation of waste activated sludge and food waste: The key role of metal oxide coated electrodes [Crossref]
- 2023 - Elimination of pesticide from high salinity wastewater by electrochlorination process: Active chlorine species and scale-up performance [Crossref]