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Positively Charged Polyamine Nanofiltration Membrane for Precise Ion-Ion Separation
Zhenyi Zhao1, Nanxi Di1, Zhiyuan Zha1
1School of Chemical Engineering and Technology, Tianjin University, Tianjin Key Laboratory of Membrane Science and Desalination Technology, State Key Laboratory of Chemical Engineering, Tianjin University, Tianjin 300072, P. R. China.
ACS Applied Materials & Interfaces
|October 5, 2023
Summary
This study introduces a novel positively charged nanofiltration membrane for precise ion separation. The new polyamine-based membrane demonstrates high selectivity for separating lithium and magnesium ions, crucial for various industrial applications.
Area of Science:
- Materials Science
- Chemical Engineering
- Environmental Science
Background:
- Conventional nanofiltration (NF) membranes face limitations in ion separation due to negative surface charges.
- Achieving high ion-ion selectivity is critical for applications like lithium-magnesium separation and water softening.
Purpose of the Study:
- To develop an advanced, positively charged nanofiltration membrane for precise ion separation.
- To overcome the performance limitations of traditional polyamide-based membranes.
Main Methods:
- Interfacial polymerization of polyethylenimine (PEI) and 1,3,5-tris(bromomethyl)benzene (TBB) to create a PEI-TBB selective layer.
- Fabrication of a composite membrane with ultrathin thickness (~95 nm) and a pore size of 6.5 Å.
- Characterization of surface charge (zeta potential +20.9 mV at pH 7) and separation performance.
Main Results:
- The PEI-TBB membrane exhibited a water permeance of 4.2 L·m⁻²·h⁻¹·bar⁻¹.
- Achieved >90% rejection for various divalent salts and separation factors >15 for NaCl/MgCl₂ and LiCl/MgCl₂.
- A three-stage NF process reduced the Mg²⁺/Li⁺ mass ratio from 50 to 0.11 with a total separation factor of 455.
Conclusions:
- The developed polyamine-based NF membrane offers precise ion-ion separation capabilities.
- Demonstrated excellent operational stability under continuous filtration and high pressure.
- Shows significant potential for applications requiring selective ion removal and recovery.
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