SCI和EI收录∣中国化工学会会刊

Chinese Journal of Chemical Engineering ›› 2022, Vol. 41 ›› Issue (1): 220-229.DOI: 10.1016/j.cjche.2021.10.023

• Fluid Dynamics and Transport Phenomena • Previous Articles     Next Articles

Molecular insights on Ca2+/Na+ separation via graphene-based nanopores: The role of electrostatic interactions to ionic dehydration

Yumeng Zhang1, Yingying Zhang1, Xueling Pan1, Yao Qin1, Jiawei Deng1, Shanshan Wang2, Qingwei Gao3, Yudan Zhu1, Zhuhong Yang1, Xiaohua Lu1   

  1. 1 College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University, Nanjing 211816, China;
    2 College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China;
    3 School of Chemical Engineering, State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China
  • Received:2021-07-20 Revised:2021-10-15 Online:2022-02-25 Published:2022-01-28
  • Contact: Yudan Zhu,E-mail address:ydzhu@njtech.edu.cn
  • Supported by:
    This work was supported by the National Science Foundation of China (21878144, 21838004 and 21776123), the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (21921006).

Molecular insights on Ca2+/Na+ separation via graphene-based nanopores: The role of electrostatic interactions to ionic dehydration

Yumeng Zhang1, Yingying Zhang1, Xueling Pan1, Yao Qin1, Jiawei Deng1, Shanshan Wang2, Qingwei Gao3, Yudan Zhu1, Zhuhong Yang1, Xiaohua Lu1   

  1. 1 College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University, Nanjing 211816, China;
    2 College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China;
    3 School of Chemical Engineering, State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China
  • 通讯作者: Yudan Zhu,E-mail address:ydzhu@njtech.edu.cn
  • 基金资助:
    This work was supported by the National Science Foundation of China (21878144, 21838004 and 21776123), the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (21921006).

Abstract: Ca2+/Na+ separation is a common problem in industrial applications, biological and medical fields. However, Ca2+ and Na+ have similar ionic radii and hydration radii, thus Ca2+/Na+ separation is challenging. Inspired by biological channels, group modification is one of the effective methods to improve the separation performance. In this work, molecular dynamics simulations were performed to investigate the effects of different functional groups (COO-, NH3+) on the separation performance of Ca2+ and Na+ through graphene nanopores under an electric field. The pristine graphene nanopore was used for comparison. Results showed that three types of nanopores preferred Ca2+ to Na+, and Ca2+/Na+ selectivity followed the order of GE-COO-(4.06) > GE (1.85) > GE-NH3+ (1.63). Detailed analysis of ionic hydration microstructure shows that different nanopores result in different hydration factors for the second hydration layer of Ca2+ and the first layer of Na+. Such different hydration factors corresponding to the dehydration ability can effectively evaluate the separation performance. In addition, the breaking of hydrogen bonds between water molecules due to electrostatic effects can directly affect the dehydration ability. Therefore, the electrostatic effect generated by group modification will affect the ionic hydration microstructure, thus reflecting the differences in dehydration ability. This in turn affects the permeable and separation performance of cations. The results of this work provide perceptive guidelines for the application of graphene-based membranes in ion separation.

Key words: Separation, Microstructure, Molecular simulation, Modified graphene nanopores, Metal-ions, Nanoconfinement

摘要: Ca2+/Na+ separation is a common problem in industrial applications, biological and medical fields. However, Ca2+ and Na+ have similar ionic radii and hydration radii, thus Ca2+/Na+ separation is challenging. Inspired by biological channels, group modification is one of the effective methods to improve the separation performance. In this work, molecular dynamics simulations were performed to investigate the effects of different functional groups (COO-, NH3+) on the separation performance of Ca2+ and Na+ through graphene nanopores under an electric field. The pristine graphene nanopore was used for comparison. Results showed that three types of nanopores preferred Ca2+ to Na+, and Ca2+/Na+ selectivity followed the order of GE-COO-(4.06) > GE (1.85) > GE-NH3+ (1.63). Detailed analysis of ionic hydration microstructure shows that different nanopores result in different hydration factors for the second hydration layer of Ca2+ and the first layer of Na+. Such different hydration factors corresponding to the dehydration ability can effectively evaluate the separation performance. In addition, the breaking of hydrogen bonds between water molecules due to electrostatic effects can directly affect the dehydration ability. Therefore, the electrostatic effect generated by group modification will affect the ionic hydration microstructure, thus reflecting the differences in dehydration ability. This in turn affects the permeable and separation performance of cations. The results of this work provide perceptive guidelines for the application of graphene-based membranes in ion separation.

关键词: Separation, Microstructure, Molecular simulation, Modified graphene nanopores, Metal-ions, Nanoconfinement