ZIF-8 derived carbon with confined sub-nanometer pores for electrochemically selective separation of chloride ions

• Published in: Separation and purification technology 2022-08, Vol.295, p.121222, Article 121222
• Main Authors: Qiao, Jie, Ma, Wenbiao, Du, Xiao, Ma, Xuli, Liu, Zhong, Li, Jun, Guan, Guoqing, Abudula, Abuliti, Hao, Xiaogang
• Format: Article
• Language: English
• Subjects: Carbonization temperature; Chloride ion; Confinement effect; Electrochemically selective separation; Sub-nanometer carbon pore; ZIF-8
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2022.121222

ZIF-8 derived carbon with confined sub-nanometer pores for electrochemically selective separation of chloride ions based on the confinement effect and difference in dehydration free energies. [Display omitted] •An electroactive carbon with confined sub-nanometer pores was obtained for Cl− removal.•Confinement effect and difference in dehydration free energies contributed to the selectivity.•The Cl− uptake capacity of the obtained electrode reached to 64.06 mg g−1.•The charge capacity of the film retained over 99.7% after 1000 cycles. Selective ion separation from aqueous solution is challenging and crucial for water purification. In this work, zeolitic imidazolate framework (ZIF-8) derived nano-porous carbon (NC-X-A) with confined sub-nanometer pores was synthesized by acid leaching and alkali activation after the carbonization of ZIF-8 precursor for the selective electrochemical separation of chloride ions (Cl−). Here, the uptake capacity and selectivity of Cl− were improved by changing the carbonization temperature to tune the specific surface area and pore size. Based on the size confinement effect and the difference in free energies of dehydration, the obtained optimum carbon film, i.e., NC-1000-A coated electrode, exhibited separation factors of 1.384, 1.952 and 2.970 for Cl−/Br−, Cl−/F− and Cl−/SO42−, respectively. It also showed fast uptake/release ability with an uptake equilibrium time less than 90 min. The Cl− uptake capacity reached to 64.06 mg g−1 and retained 99.7% of its initial value even after 1000 uptake/release cycles due to its porous structure with high specific surface area, good electrical conductivity and extra electric driving force during the ESIX process. Thus, it is expected that this kind of carbon film would be applied as a promising electroactive material for the selective separation of Cl− from wastewater.