| Metadata | Details |
|---|
| Publication Date | 2020-01-01 |
| Journal | Manufacturing Review |
| Authors | Mattia Pierpaoli, MichaĹ Rycewicz, Aneta Ĺuczkiewicz, Sylwia FudalaâKsiÄ
Ĺźek, Robert Bogdanowicz |
| Institutions | Marche Polytechnic University, GdaĹsk University of Technology |
| Citations | 16 |
| Analysis | Full AI Review Included |
- Problem Statement: Electrochemical Oxidation (EO) is effective for treating refractory landfill leachate, but high-performance anodes often rely on Critical Raw Materials (CRMs) like Platinum (Pt), Iridium (Ir), and Ruthenium (Ru), leading to high cost and supply risk.
- Methodology: A âCritical Indexâ (Ci) was developed, quantifying the criticality of electrode materials based on the EU CRM list (Supply Risk and Economic Importance), weighted by the material composition in the active layer.
- Key Finding (BDD): Boron-Doped Diamond (BDD) electrodes offer the best compromise, achieving high Chemical Oxygen Demand (COD) removal efficiency (median ~75%) with a significantly low Critical Index (Ci: 0.084-0.168).
- CRM-Heavy Anodes: Noble metal (Pt) electrodes exhibited the highest Ci (up to 14), confirming their unsuitability for large-scale, sustainable applications despite high stability.
- Performance Correlation: For Single Metal Oxide (SMO) and Multi-Metal Oxide (MMO) electrodes, there is a general trend showing that higher CRM content (higher Ci) correlates with increased COD removal efficiency.
- CRM-Free Alternatives: Amorphous Carbon (a-C) electrodes are CRM-free (Ci = Absent) but suffer from the lowest removal efficiency (median COD removal ~25%) and pronounced corrosion.
- Conclusion: BDD is validated as the preferential material for sustainable, high-efficiency EO of heavily polluted landfill leachates, minimizing reliance on CRMs.
| Parameter | Value | Unit | Context |
|---|
| COD Initial Concentration (Median) | 1870 | mg O2/l | Median initial concentration across 115 observations. |
| COD Removal Efficiency (BDD, Median) | ~75 | % | Highest median efficiency among tested electrode types. |
| COD Removal Efficiency (a-C, Median) | ~25 | % | Lowest median efficiency, limited by corrosion. |
| N-NH4 Initial Concentration (Range) | 300 to 3000 | mg/m3 | Typical range for ammonium nitrogen in analyzed leachates. |
| Critical Index (Ci) - Noble Metal (Pt) | 0.003 to 14 | - | Highest criticality, reflecting high Pt content and cost. |
| Critical Index (Ci) - BDD | 0.084 to 0.168 | - | Low criticality, high performance. |
| Critical Index (Ci) - MMO (Range) | 0.023 to 4.9 | - | Varies based on specific oxide composition (e.g., IrO2, RuO2, Ta2O5). |
| Specific Electrical Charge (Range) | 0 to 60 | Ah/m3 | Range used for performance comparison plots. |
| Typical DSA Coating Thickness | 0.24 | mg/cm2 | Example for Ti/Ru-Sn-Ti electrode (Kim et al. [30]). |
| BDD Deposition Method | MPCVD | - | Microwave Plasma-Assisted Chemical Vapor Deposition. |
- Data Collection: 112 experimental observations were compiled from 25 publications focusing on the electrochemical oxidation of landfill leachate, classifying electrodes into six categories (Noble Metal, SMO, MMO, PbO2, a-C, BDD).
- Performance Quantification: Chemical Oxygen Demand (COD) and Ammonium-Nitrogen (N-NH4) removal efficiencies were extracted or estimated from published data. Specific Electrical Charge (Q) was calculated (Q = JAt/V) to normalize performance across different scales and durations.
- Critical Index (Ci) Calculation: The Ci was computed using the Euclidean distance method, integrating:
- Supply Risk (SRj) and Economic Importance (EIj) indexes from the 2017 EU CRM list.
- The elemental fraction ratio (aj) and atomic weight (AWj) of the active electrode layer.
- Normalization by the electrode area (A).
- Material Composition Determination:
- For SMO/MMO (DSA) electrodes, the nominal or effective elemental composition of the oxide coating was used.
- For BDD electrodes, the amount of boron was calculated based on the diborane gas used during the MPCVD growth process.
- For Noble Metal and a-C electrodes, the entire electrode mass was considered for Ci calculation.
- Correlation Analysis: Boxplots and scatter plots were generated to visualize the relationship between the calculated Critical Index (Ci) and the measured COD and N-NH4 removal efficiencies for each electrode type.
- Wastewater Treatment (Leachate): Direct application for treating highly contaminated landfill leachate, providing a high-efficiency, sustainable alternative to traditional methods that struggle with refractory pollutants.
- Advanced Oxidation Processes (AOPs): Integration of BDD-based EO systems into industrial and municipal wastewater treatment plants to mineralize persistent organic pollutants (POPs) and micropollutants of emerging concern.
- Sustainable Electrochemical Manufacturing: Replacement of CRM-dependent anodes (Pt, IrO2, RuO2) with BDD in large-scale electrochemical reactors, improving supply chain security and reducing material costs.
- Water Reuse and Recycling: Utilizing BDDâs high stability and wide potential window to achieve complete mineralization of contaminants, enabling the safe reuse of treated water streams.
- Electrochemical Synthesis: Application in processes requiring extremely stable, chemically inert anodes, leveraging BDDâs resistance to corrosion and high activity toward indirect oxidation mechanisms (e.g., chlorine/hypochlorite generation).
View Original Abstract
Landfill leachate possesses high concentrations of ammonia, micropollutants, and heavy metals, and are characterised for low biodegradability. For this reason, conventional treatment technologies may result ineffective for complete pollutant removal. Electrochemical oxidation allows most of the of recalcitrant pollutants to be oxidised effectively within an easy operational and acceptable retention time, without the need to provide additional chemicals, and without producing waste materials. The mineralisation efficiency and electrode durability depend on the nature of the electrode material. The conventionally adopted anodes can contain critical raw materials (CRMs), and are subject to extreme corrosion conditions. CRM-free electrodes, such as carbon and graphite-based, exhibit a lower efficiency, and are subject to faster deactivation, or, as for lead-dioxide-based electrodes, can constitute a hazard due to the release into the effluent of the coating corrosion products. In this study, the relationship between electrode type, CRM content, and the removal efficiencies of organic compounds and ammonium-nitrogen (N-NH 4 ) was investigated. Material criticality was estimated by the supply risk with economic importance indexes reported in the 2017 EU CRM List. The COD and N-NH 4 removal efficiencies were obtained from a literature analysis of 25 publications. The results show that, while single and multi-oxide-coated electrodes may contain low amounts of CRM, but with limited efficiency, boron-doped diamonds (BDD) may constitute the best compromise in terms of a reduced content of CRM and a high mineralisation efficiency.