Preparation of highly positively charged NF membranes with surface quaternization modification and Li+/Mg2+ separation performance

doi:10.11949/0438-1157.20241174

Abstract

Abstract:

Positive charge modification of nanofiltration membrane surface is expected to improve lithium-magnesium separation selectivity, but conventional surface positive charge modification methods are inefficient, the positive charge density of the membrane surface is low, the electrostatic shielding effect is difficult to eliminate, and the improvement of lithium-magnesium selectivity is limited. In this study, polyethyleneimine (PEI) molecules rich in amine groups were grafted onto the surface of a commercial polyamide nanofiltration membrane, creating a surface-modified membrane (PEI/PA). The surface amine groups were then quaternized in situ through alkylation, producing a membrane with significantly enhanced positive charge (N-alkyl@PEI/PA). After modification, the isoelectric point of the membrane surface increased from 4.4 to 7.9, indicating a successful enhancement of surface charge. The performance of the modified membrane was further evaluated using a Li⁺/Mg²⁺ mixture with a concentration of 1000 mg·L^-1 and a mass ratio of 10∶1. The results showed that surface modification had minimal impact on membrane flux. At pH 6.8, its Li⁺/Mg²⁺ separation factor reached 35.7. At pH 9.7, the reduced protonation and weakened positive charge of the PEI/PA membrane led to a 72% decrease in lithium-magnesium selectivity, whereas the N-alkyl@PEI/PA membrane, with its higher positive charge, exhibited a smaller decline in performance, maintaining a separation factor of 21.9. This demonstrates the membrane’s potential for efficient Li⁺/Mg²⁺ separation across a broad pH range.

Key words: nanofiltration, nitrogen alkylation reaction, Li⁺/Mg²⁺ separation, Donnan effect, selectivity

摘要：

纳滤膜表面荷正电改性有望提高锂镁分离选择性，但常规表面荷正电改性方法效率不高，膜表面荷正电密度低，静电屏蔽作用难消除，锂镁选择性提升有限。利用氮烷基化对表面接枝聚乙烯亚胺的纳滤膜（PEI/PA膜）表面胺基进行原位季铵化改性，制得荷正电性强化的纳滤膜（N-alkyl@PEI/PA膜）。改性后膜表面等电点从4.4提升至7.9，膜表面荷正电强度显著提高。结果表明，表面改性过程对膜通量影响较小。表面季铵化改性膜在不同pH条件下的锂镁混合溶液分离中，展示出稳定的锂镁分离性能。在pH=6.8时，其锂镁分离因子达35.7；在pH=9.7时，PEI/PA膜由于表面质子化程度降低，荷正电性减弱，其锂镁选择性降至10.1，降幅达72%，而N-alkyl@PEI/PA膜得益于膜表面季铵基团的高电离程度及荷正电强度，其锂镁选择性仍维持在21.9。本研究为提高纳滤膜在宽pH范围内锂镁分离性能的稳定性提供了参考。

关键词: 纳滤, 氮烷基化反应, 锂镁分离, Donnan排斥效应, 选择性

CLC Number:

TQ 028.8

Xinchen XIANG, Dan LU, Ying ZHAO, Zhikan YAO, Ruiqiang KOU, Danjun ZHENG, Zhijun ZHOU, Lin ZHANG. Preparation of highly positively charged NF membranes with surface quaternization modification and Li⁺/Mg²⁺ separation performance[J]. CIESC Journal, 2025, 76(5): 2377-2386.

向昕辰, 鲁丹, 赵影, 姚之侃, 寇瑞强, 郑丹军, 周志军, 张林. 聚酰胺纳滤膜表面季铵化提高荷正电性及其锂镁分离性能[J]. 化工学报, 2025, 76(5): 2377-2386.

Figures/Tables 10

Fig.1 Construction of positively charged active layer by EDC/NHS

Fig.2 Preparation of N-alkyl@PEI/PA membrane by N-alkylation method

Fig.3 PEI grafting concentration optimization: (a) the effect of PEI concentration on the content of surface amine groups; (b) rejection performance of modified membranes with different PEI concentrations for MgCl2 solution at pH 6.8

Fig.4 Optimization of N-alkylation reaction conditions: (a) optimization of sodium hydroxide concentration; (b) optimization of iodomethane concentration

Fig.5 The surface and cross-section SEM of NF membranes: (a) PA membrane; (b) PEI/PA membrane; (c) N-alkyl@PEI/PA membrane

Fig.6 The surface group content of different membrane: (a) amine group; (b) carboxyl group

Fig.7 The Zeta potential of different membrane at different pH

Fig.8 Single salt separation performance of membranes: (a) MgCl2 solution at pH 6.8; (b) MgCl2 solution at pH 9.7; (c) LiCl solution at pH 6.8; (d) LiCl solution at pH 9.7

Fig.9 Mixed salt (Li+∶Mg2+ = 1∶10) separation performance of membrane: (a) Mg2+ rejection at different pH; (b) Li+ rejection at different pH; (c) separation factor at different pH

Table 1 Comparison of experimental Li+/Mg2+ separation factors with data in literature

膜类型	压力/bar	混盐浓度/(mg·L^-1)	镁锂比	pH	分离因子	文献
N-alkyl@PEI/PA	6	10	1000	6.8	35.7	本文
NF90	16	20	2000	6.0	2.1	[26]
DK	16	24	4940	7.0	3.2	[26]
TFC-MeOH	6	24	1000	7.6	5.77	[27]
TFC-1	6	24	1000	7.6	9.36	[27]
TFC-2	6	24	1000	7.6	9.8	[27]
TFC-3	6	24	1000	7.6	11.38	[27]
TFC-4	6	24	1000	7.6	11.15	[27]
PEI-g-PA	4	73	2000	7.0	23.9	[28]
PES/(CNC-COOH)/PEI/TMC	4	20	2000	7.0	12.2	[28]
MCPM-2.0	2	1.54	1000	7.0	18	[28]
PEI/TMC-PDA-gC₃N₄ (M4)	4	20	2000	7.3	13.39	[29]
PEI/TMC-PDA-gC₃N₄ (M5)	4	48	2000	7.3	10.77	[29]
NF-IL-2	6	20	2000	7.9	8.12	[30]
PBI_12-25K	6	10	2000	7.9	15.15	[30]

References 30

1	赵显赫, 耿光超, 龚裕仲, 等. 基于深度学习的储能锂离子电池健康状态估计[J]. 能源工程, 2022, 42(4): 28-35.
	Zhao X H, Geng G C, Gong Y Z, et al. Real-time state of health estimation of lithium ion battery in energy storage power station based on deep learning[J]. Energy Engineering, 2022, 42(4): 28-35.
2	Zhang Y, Wang L, Sun W, et al. Membrane technologies for Li⁺/Mg²⁺ separation from salt-lake brines and seawater: a comprehensive review[J]. Journal of Industrial and Engineering Chemistry, 2020, 81: 7-23.
3	Nagata M, Saraswat A, Nakahara H, et al. Miniature pin-type lithium batteries for medical applications[J]. Journal of Power Sources, 2005, 146(2): 762-765.
4	蒋晨啸, 陈秉伦, 张东钰, 等. 我国盐湖锂资源分离提取进展[J]. 化工学报, 2022, 73(2): 481-503.
	Jiang C X, Chen B L, Zhang D Y, et al. Progress in isolating lithium resources from China salt lake brine[J]. CIESC Journal, 2022, 73(2): 481-503.
5	Zhang N, Yu H C, Zhang J D, et al. Pressure-driven Li⁺/Mg²⁺ selective permeation through size-sieving nanochannels: the role of the second hydration shell[J]. Separation and Purification Technology, 2023, 327: 124818.
6	吴雨茜, 唐元晖, 郭强, 等. 纳滤膜对硫酸型解吸液锂镁分离的实验研究与模拟[J]. 化工学报, 2024, 75(12): 4563-4575.
	Wu Y X, Tang Y H, Guo Q, et al. Experimental study and simulation on nanofiltration separation of lithium and magnesium from sulfate desorption solution[J]. CIESC Journal, 2024, 75(12): 4563-4575.
7	Bai R B, Wang J F, Wang D G, et al. Selective separation of lithium from the high magnesium brine by the extraction system containing phosphate-based ionic liquids[J]. Separation and Purification Technology, 2021, 274: 119051.
8	Ying J D, Luo M J, Jin Y, et al. Selective separation of lithium from high Mg/Li ratio brine using single-stage and multi-stage selective electrodialysis processes[J]. Desalination, 2020, 492: 114621.
9	Lu D, Yao Z K, Jiao L, et al. Separation mechanism, selectivity enhancement strategies and advanced materials for mono-/multivalent ion-selective nanofiltration membrane[J]. Advanced Membranes, 2022, 2: 100032.
10	Sun X S, Wang X Z, Wan Y L, et al. Synthesis of functional ionic liquids with high extraction rate and electroconductivity for lithium-magnesium separation and metallic magnesium production from salt lake brine[J]. Chemical Engineering Journal, 2023, 452: 139610.
11	Wang R Y, Lin S H. Pore model for nanofiltration: history, theoretical framework, key predictions, limitations, and prospects[J]. Journal of Membrane Science, 2021, 620: 118809.
12	Wang R Y, Biesheuvel P M, Elimelech M. Extended Donnan model for ion partitioning in charged nanopores: application to ion-exchange membranes[J]. Journal of Membrane Science, 2024, 705: 122921.
13	Li Y, Zhao Y J, Wang H Y, et al. The application of nanofiltration membrane for recovering lithium from salt lake brine[J]. Desalination, 2019, 468: 114081.
14	Peng H, Zhao Q. A nano-heterogeneous membrane for efficient separation of lithium from high magnesium/lithium ratio brine[J]. Advanced Functional Materials, 2021, 31: 2009430.
15	Zhang H R, He Q M, Luo J Q, et al. Sharpening nanofiltration: strategies for enhanced membrane selectivity[J]. ACS Applied Materials & Interfaces, 2020, 12(36): 39948-39966.
16	叶海星, 陈宇昊, 陈仪, 等. 镁锂分离复合纳滤膜研究进展[J]. 化工进展, 2023, 42(4): 1934-1943.
	Ye H X, Chen Y H, Chen Y, et al. Research progress of composite nanofiltration membrane for magnesium and lithium separation[J]. Chemical Industry and Engineering Progress, 2023, 42(4): 1934-1943.
17	Li Q, Liu Y H, Jia Y L, et al. High performance Li⁺/Mg²⁺ separation membrane by grafted short chain amino-rich monomers[J]. Journal of Membrane Science, 2023, 677: 121634.
18	Zhang Y N, Yu D H, Jia C Y, et al. Advances and promotion strategies of membrane-based methods for extracting lithium from brine[J]. Desalination, 2023, 566: 116891.
19	Dey T K, Bindal R C, Prabhakar S, et al. Development, characterization and performance evaluation of positively-charged thin film-composite nanofiltration membrane containing fixed quaternary ammonium moieties[J]. Separation Science and Technology, 2011, 46(6): 933-943.
20	Zhao Y, Li N, Shi J, et al. Extra-thin composite nanofiltration membranes tuned by γ-cyclodextrins containing amphipathic cavities for efficient separation of magnesium/lithium ions[J]. Separation and Purification Technology, 2022, 286: 120419.
21	Li Q, Liu Y H, Ji Y H, et al. Mg²⁺/Li⁺ separation by electric field assisted nanofiltration: the impacts of membrane pore structure, electric property and other process parameters[J]. Journal of Membrane Science, 2022, 662: 120982.
22	Staros J V, Wright R W, Swingle D M. Enhancement by N-hydroxysulfosuccinimide of water-soluble carbodiimide-mediated coupling reactions[J]. Analytical Biochemistry, 1986, 156(1): 220-222.
23	Peng J M, Su Y L, Chen W J, et al. Polyamide nanofiltration membrane with high separation performance prepared by EDC/NHS mediated interfacial polymerization[J]. Journal of Membrane Science, 2013, 427: 92-100.
24	Smith M B. March's Advanced Organic Chemistry: Reactions, Mechanisms, and Structure[M]. 5th ed. Hoboken: Wiley, 2013.
25	鲁丹, 向昕辰, 耿艺方, 等. 面向盐湖提锂的聚酰胺纳滤膜设计策略[J]. 盐湖研究, 2025, 33(1): 100-112.
	Lu D, Xiang X C, Geng Y F, et al. Design strategy of polyamide nanofiltration membrane for lithium extraction from salt lake brines[J]. Journal of Salt Lake Research, 2025, 33(1): 100-112.
26	Zhai J, Balogun A, Bhattacharjee S, et al. Nanofiltration as pretreatment for lithium recovery from salt lake brine[J]. Journal of Membrane Science, 2024, 710: 123150.
27	Zhang S Y, Zhang R N, Li R L, et al. Guanidyl-incorporated nanofiltration membranes toward superior Li⁺/Mg²⁺ selectivity under weakly alkaline environment[J]. Journal of Membrane Science, 2022, 663: 121063.
28	Yuan B B, Zhao S H, Xu S J, et al. Aliphatic polyamide nanofilm with ordered nanostripe, synergistic pore size and charge density for the enhancement of cation sieving[J]. Journal of Membrane Science, 2022, 660: 120839.
29	Luo H, Peng H W, Zhao Q. High flux Mg²⁺/Li⁺ nanofiltration membranes prepared by surface modification of polyethylenimine thin film composite membranes[J]. Applied Surface Science, 2022, 579: 152161.
30	Ashraf M A, Wang J F, Wu B C, et al. Enhancement in Li⁺/Mg²⁺ separation from salt lake brine with PDA-PEI composite nanofiltration membrane[J]. Journal of Applied Polymer Science, 2020, 137(47): e49549.

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Preparation of highly positively charged NF membranes with surface quaternization modification and Li⁺/Mg²⁺ separation performance

聚酰胺纳滤膜表面季铵化提高荷正电性及其锂镁分离性能

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