Achieving Sustainable Development Goal 6 Electrochemical-Based Solution for Treating Groundwater Polluted by Fuel Station

At a Glance

Metadata	Details
Publication Date	2022-09-17
Journal	Water
Authors	Júlio César Oliveira da Silva, Aline Maria Sales Solano, Inalmar D. Barbosa Segundo, Elisama Vieira dos Santos, Carlos A. Martínez‐Huitle
Institutions	Universidade Federal do Rio Grande do Norte, Johannes Gutenberg University Mainz
Citations	13
Analysis	Full AI Review Included

Technical Analysis & Documentation: MPCVD Diamond for Advanced Water Treatment

Reference: da Silva et al. (2022). Achieving Sustainable Development Goal 6 Electrochemical-Based Solution for Treating Groundwater Polluted by Fuel Station. Water, 14, 2911.

Executive Summary

This research validates the use of Electrochemical Advanced Oxidation Processes (EAOPs) for achieving Sustainable Development Goal 6 (SDG 6) by effectively treating groundwater contaminated by petroleum fuels (BTEX compounds).

Application: High-efficiency removal of BTEX, Phenol, and Total Petroleum Hydrocarbons (TPHs) from real-world contaminated groundwater matrices.
Material Comparison: Three anode materials (Ti/RuO₂, Ti/Pt, and Niobium-supported Boron-Doped Diamond (Nb/BDD)) were compared for their electrocatalytic efficiency in COD and TOC removal.
BDD Performance: Nb/BDD anodes demonstrated superior intrinsic oxidation performance, achieving high COD removal (78.2% at 30 mA cm^-2) due to the efficient electrogeneration of physisorbed hydroxyl radicals (•OH), favoring complete electrochemical incineration.
Mineralization Efficiency: Ti/RuO₂ achieved the highest TOC removal (64.61%) in batch tests, while Nb/BDD achieved 51.74%, confirming BDD’s strong potential for mineralization.
Scale-Up Validation: A 5 L pilot flow plant using a double-sided Ti/RuO₂ anode achieved 87% COD abatement and reduced BTEX concentrations to below Brazilian regulatory limits (except Xylene), demonstrating industrial viability.
Energy Metrics: The process is energy-viable, with the lowest energy consumption recorded at 0.050 kWh gCOD^-1 using Ti/RuO₂ at 30 mA cm^-2 with Na₂SO₄ electrolyte.

Technical Specifications

The following hard data points were extracted from the batch and pilot-scale experiments, highlighting the performance of the electrocatalytic materials.

Parameter	Value	Unit	Context
Initial COD Concentration	230	mg L^-1	Untreated groundwater effluent
Initial Xylene Concentration	5435.5	µg L^-1	Highest BTEX pollutant concentration
Current Density (Batch & Pilot Optimum)	30	mA cm^-2	Optimized operating condition
Electrolyte Concentration	0.5	M	Na₂SO₄ supporting salt
COD Removal (Nb/BDD, Batch)	78.2	%	At 30 mA cm^-2 (without Na₂SO₄)
TOC Removal (Nb/BDD, Batch)	51.74	%	Mineralization efficiency
COD Abatement (Ti/RuO₂, Pilot)	87	%	After 300 min treatment
Xylene Removal (Ti/RuO₂, Pilot)	90	%	Reduced from 5435.5 to 500 µg L^-1
Energy Consumption (Ti/RuO₂, Batch Optimum)	0.050	kWh gCOD^-1	Lowest EC achieved (with Na₂SO₄)
Energy Consumption (Ti/RuO₂, Pilot)	2.53	kWh kg COD^-1	Total energy required for 300 min
Operating Temperature	25	°C	Ambient condition

Key Methodologies

The study utilized both batch and flow-cell electrochemical reactors to evaluate the degradation efficiency under varying conditions.

Anode Selection and Preparation: Three distinct anode types were employed: Ti/RuO₂ (active), Ti/Pt (active), and Nb/BDD (non-active, high-performance).
Batch Reactor Testing: Initial comparative tests were conducted in a 0.5 L constantly mixed batch cell, applying current densities of 10, 30, and 60 mA cm^-2 over 240 minutes.
Electrolyte Optimization: The effect of increased conductivity and enhanced oxidant generation was studied by adding 0.5 M Na₂SO₄ as a supporting electrolyte.
BDD Mechanism Validation: The superior performance of BDD was attributed to the weak adsorption of •OH radicals on the non-active diamond surface, promoting complete electrochemical incineration (conversion to CO₂ and water).
Pilot Scale-Up: The optimized conditions (30 mA cm^-2 and 0.5 M Na₂SO₄) were applied to a 5 L pilot flow plant using a double-sided Ti/RuO₂ anode and stainless steel cathodes to verify industrial viability.
Performance Metrics: Degradation was quantified by monitoring COD, TOC, and specific BTEX compound concentrations (Benzene, Toluene, Ethylbenzene, Xylene) via GC-MS.

6CCVD Solutions & Capabilities

The research confirms that Boron-Doped Diamond (BDD) anodes are critical for achieving the highest levels of pollutant mineralization through electrochemical incineration. While the authors selected Ti/RuO₂ for scale-up based on immediate “eco-technological suitability,” 6CCVD specializes in providing high-performance BDD materials that offer superior long-term stability and oxidative power, essential for treating highly recalcitrant pollutants like those found in fuel leaks.

Applicable Materials for Replication and Extension

To replicate the high-performance oxidation achieved by the Nb/BDD anode and to extend the research toward full mineralization (TOC removal), 6CCVD recommends the following materials:

6CCVD Material	Description & Application	Key Benefit for EAOPs
Heavy Boron-Doped Diamond (BDD)	MPCVD BDD films grown on conductive substrates (Niobium, Silicon, or Tungsten).	Highest overpotential for oxygen evolution, maximizing physisorbed •OH generation for complete pollutant incineration.
Custom BDD Substrates	BDD films grown directly on Niobium (Nb) or Titanium (Ti) substrates, matching the configuration used in the study (Nb/BDD).	Ensures robust electrical contact and mechanical stability required for high current density flow cells.
Polycrystalline Diamond (PCD) Substrates	Large-area PCD plates for cost-effective, high-throughput reactor designs.	Available in plates up to 125mm, ideal for scaling up industrial flow reactors beyond the 5 L pilot stage.

Customization Potential for Electrochemical Reactors

6CCVD provides comprehensive customization services necessary to transition laboratory-scale BDD performance into robust industrial solutions:

Custom Dimensions and Thickness: We supply BDD plates and wafers in custom dimensions up to 125mm (PCD/BDD), with film thicknesses ranging from 0.1 µm to 500 µm, allowing engineers to optimize electrode area (A) and mass transport conditions (km) for specific flow cell designs.
Substrate Flexibility: We offer BDD deposition on various conductive substrates (Ti, Nb, W, Si) to meet the mechanical and electrical requirements of the reactor, ensuring compatibility with high current densities (up to 60 mA cm^-2 and beyond).
Advanced Metalization Services: For integrating BDD electrodes into flow cells, reliable electrical contacts are essential. 6CCVD offers in-house metalization capabilities, including deposition of Au, Pt, Ti, and W layers, ensuring stable, low-resistance connections under aggressive electrochemical conditions.
Polishing and Surface Finish: We provide polishing services (Ra < 5 nm for inch-size PCD/BDD) to optimize surface morphology, which is critical for controlling mass transport and maximizing the efficiency of the electrogenerated oxidants.

Engineering Support

6CCVD’s in-house PhD team specializes in the material science of diamond electrochemistry. We can assist researchers and engineers with material selection and optimization for similar Groundwater Remediation and Advanced Oxidation projects, focusing on:

Tuning the boron concentration to optimize the BDD surface for maximum sulfate radical (SO₄•¯) or hydroxyl radical (•OH) generation, depending on the effluent matrix.
Designing custom electrode geometries and metalization schemes for high-efficiency, double-sided flow cell reactors, similar to the pilot plant used in this study.
Consultation on achieving the optimal sp²/sp³ ratio in the BDD film to maximize stability and lifetime under continuous high current density operation.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Oil leakage occurs at fuel service stations due to improper storage, which pollutes soil and, subsequently, can reach the groundwater. Many compounds of petroleum-derived fuels pose hazards to aquatic systems, and so must be treated to guarantee clean and safe consumption, which is a right proposed by the United Nations in their Sustainable Development Goal 6 (SDG 6: Clean Water and Sanitation). In this study, contaminated groundwater with emerging pollutants by petroleum-derived fuel was electrochemically treated in constantly mixed 0.5 L samples using three different anodes: Ni/BDD, Ti/Pt, Ti/RuO2. Parameters were investigated according to chemical oxygen demand (COD), energy consumption analysis, by applying different electrodes, current densities (j), time, and the use of Na2SO4 as an electrolyte. Despite a similar COD decrease, better degradation was achieved after 240 min of electrochemical treatment at Ti/RuO2 system (almost 70%) by applying 30 mA cm−2, even without electrolyte. Furthermore, energy consumption was lower with the RuO2 anode, and greater when 0.5 M of Na2SO4 was added; while the order, when compared with the other electrocatalytic materials, was Ti/RuO2 > Ti/Pt > Ni/BDD. Thereafter, aiming to verify the viability of treatment at a large scale, a pilot flow plant with a capacity of 5 L was used, with a double-sided Ti/RuO2 as the anode, and two stainless steel cathodes. The optimal conditions for the effective treatment of the polluted water were a j of 30 mA cm−2, and 0.5 M of Na2SO4, resulting in 68% degradation after 300 min, with almost complete removal of BTEX compounds (benzene, toluene, ethyl-benzene, and xylene, which are found in emerging pollutants) from the water and other toxic compounds. These significant results proved that the technology used here could be an effective SDG 6 electrochemical-based solution for the treatment of groundwater, seeking to improve the quality of water, removing contaminants, and focusing on Brazilian environmental legislations and, consequently, converting pollutants into effluent that can be returned to the water cycle.

Tech Support

Original Source

DOI: https://doi.org/10.3390/w14182911

References

2021 - Policy experience with groundwater protection from diffuse pollution—A review [Crossref]
2021 - Evaluating the ability of transformed urban agglomerations to achieve Sustainable Development Goal 6 from the perspective of the water planet boundary: Evidence from Guanzhong in China [Crossref]
2019 - The potential evaluation of groundwater pollution based on the intrinsic and the specific vulnerability index [Crossref]
2020 - Polychlorinated Biphenyls and Polycyclic Aromatic Hydrocarbons in Groundwater of Fuel-Impacted Areas in Ado-Ekiti, Nigeria [Crossref]
2018 - Increasing removal of benzene from groundwater using stacked tubular air-cathode microbial fuel cells [Crossref]
2016 - Enhanced bioremediation of TCE-contaminated groundwater with coexistence of fuel oil: Effectiveness and mechanism study [Crossref]
2014 - Climate change and challenges of water and food security [Crossref]
2018 - Electrochemical oxidation of organic pollutants for wastewater treatment [Crossref]