Key Takeaways & Executive Findings
- •• Coal tar pitch-based nanosheets (CPN-9) exhibit high specific surface area (466.34 m2/g) and hierarchical porosity, enhancing ion transport and accessibility. • Nitrogen doping (pyrrolic and pyridinic N) synergistically improves electron transfer and reduces charge transfer resistance, boosting capacitive performance. • In flow-electrode capacitive deionization (FCDI), CPN-9 achieves a desalination rate of 0.039 mg/(cm2 min) with high charge efficiency (48.47%) and low energy consumption (0.012 kWh/mol). • The study provides a sustainable route for high-salinity wastewater treatment using coal-derived carbon materials, addressing environmental challenges in mining regions.
Abstract
High-salinity wastewater treatment has always been a challenging issue. In this study, coal tar pitch was used as the carbon source and melamine as the nitrogen source to prepare coal tar pitch-based nanosheets (CPN-9) using a salt-template method. The desalination performance of CPN-9 was evaluated using flow-electrode capacitive deionization technology. The results showed that CPN-9 has a high specific surface area (466.34 m2/g), a rich pore structure (micro-/meso-pore volume was 0.28), excellent rheological properties, and hydrophilicity (contact angle of 20.44°), thereby accelerating ion transport. Electrochemical results indicated that CPN-9 exhibits a significant double-layer ion storage mechanism, with a specific capacitance of 176.66 F/g at a current density of 0.5 A/g. CPN-9 has a very low charge transfer resistance. The synergistic effect of aromatic carbon and nitrogen doping (the content of pyrrole and pyridine nitrogen was 36.40% and 35.83%, respectively) in coal tar pitch accelerates electron transfer in CPN-9. The good ion diffusion performance and low impedance of CPN-9 accelerate the ion exchange rate, resulting in outstanding desalination performance. At 1.2 V and 3% mass loading, with a CPN-9 to conductive carbon black ratio of 4:1, the average desalination rate, charge efficiency, and energy consumption reached 0.039 mg/(cm2 min), 48.47%, and 0.012 kWh/mol, respectively. In summary, this study optimized the structure of CPN-9 from the perspective of electronic and ionic transport, enhancing its desalination performance and providing theoretical support for the deionization of high-salinity wastewater.
1. Introduction
Water resources are the foundation for maintaining the health of ecosystems and the socio-economic development. However, global water resources are facing unprecedented pressure. Therefore, there is an encouragement to carry out in-depth treatment and research on the reuse of highly saline water bodies, as well as the promotion of non-traditional water sources such as mine water and urban reclaimed water [1–3]. In the process of mining and processing of coal, a large amount of groundwater and surface water comes into contact with salt deposits and rock salt mines, dissolving mineral substances, leading to wastewater rich in sodium salts. The direct discharge of high-concentration sodium salt wastewater can cause pollution to the surrounding soil, groundwater, and surface water bodies, posing a threat to the ecological environment. In addition, the discharge of high-salinity wastewater can also affect downstream water bodies, leading to long-term negative impacts on aquatic ecosystems [2,4]. Therefore, it is extremely necessary to manage the wastewater from mines, not only to reduce its negative impact on the environment, but also to promote the recycling of water resources, alleviating the urgency of industrial water use [3].
Capacitive deionization (CDI) technology is a promising technology for desalination of water. It is a more cost-effective and energy-efficient alternative to reverse osmosis and distillation for desalination of brackish water [5,6]. Fixed electrodes have limitations in terms of increased electro sorption, and regeneration of desalination efficiency of the saline water. Flow electrode capacitor deionization (FCDI) addresses these bottlenecks.
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Jincai Ran, Zhaoyang Song, Qiongqiong He, Zhenyong Miao (2025). Coal pitch-based nanosheets enhance the electronic and ionic transport of flow electrode capacitive deionization. SinoTechIntel Verified Research. https://doi.org/10.1016/j.ijmst.2025.03.008
Research & Educational Purpose Only:The translations, structured abstracts, analytical annotations, and data reports provided by SinoTechIntel are intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
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Frequently Asked Questions
What is the main innovation of this study?
The study develops coal tar pitch-based nanosheets (CPN-9) via a salt-template method with nitrogen doping, which significantly enhances both electronic and ionic transport, leading to superior desalination performance in flow-electrode capacitive deionization (FCDI).
How does CPN-9 improve desalination performance?
CPN-9 exhibits a high specific surface area (466.34 m2/g), hierarchical pore structure, excellent hydrophilicity, and low charge transfer resistance. Nitrogen doping (pyrrolic and pyridinic) accelerates electron transfer, while the porous structure facilitates ion diffusion, resulting in a high desalination rate of 0.039 mg/(cm2 min) and low energy consumption.
What are the key electrochemical properties of CPN-9?
CPN-9 shows a specific capacitance of 176.66 F/g at 0.5 A/g, a significant double-layer ion storage mechanism, and very low charge transfer resistance, indicating excellent electrochemical performance for capacitive deionization.
What is the significance of using coal pitch as a precursor?
Coal pitch is an abundant and low-cost byproduct of coal processing. Utilizing it as a carbon source for high-performance desalination materials provides a sustainable and economically viable approach for treating high-salinity wastewater, especially in coal mining regions.
What are the practical implications of this research?
The findings offer a promising method for efficient and energy-saving desalination of mine water and other high-salinity wastewaters, contributing to environmental protection and water resource recycling in industrial applications.
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