Preparation and performance of bilayer polyvinylidene fluoride ultrafiltration membranes based on green solvents

doi:10.19965/j.cnki.iwt.2025-0117

Abstract

Abstract:

In response to the toxic solvent contamination and safety issues in the traditional preparation process of ultrafiltration membranes, non-toxic and biodegradable methyl lactate (ML) and propylene carbonate (PC) were selected as green solvents. Non-solvent-induced phase separation (NIPS) and thermally-induced phase separation (TIPS) techniques were used to successfully prepare a bilayer structure polyvinylidene fluoride (PVDF) ultrafiltration membrane in a mild environment. The good compatibility of ML/PC composite solvent and PVDF was confirmed by Hansen solubility parameter evaluation, and the appropriate temperature range of the membrane preparation process was determined by the gel transition temperature test. The formation process of ultrafiltration membrane in green solvent system was analyzed, and the effect of bilayer structure on membrane performance was investigated. The results showed that the support layer prepared using PVDF/ML/PC system was loose and porous, which was conducive to the osmotic transport of water molecules, while the selective layer prepared using PVDF/ML system was dense and could provide good retention performance. The bilayer ultrafiltration membrane composed of the two layers was dense and defect free on the surface, and the water contact angle decreased from 108.27° to 79.75°, resulting in improved hydrophilicity. The membrane cross-section structures were all in the form of bicontinuous fiber intertwining, with excellent mechanical properties, and the elongation at break was as high as 481.8%. This ultrafiltration membrane exhibited excellent filtration capacity, with a pure water flux of 2 006.0 L/(m²·h·MPa), a BSA retention rate of up to 99.9%, and a protein adsorption of no more than 5.0×10^-5 g/cm².

Key words: methyl lactate, propylene carbonate, bilayer structure, polyvinylidene fluoride ultrafiltration membrane

摘要：

针对超滤膜传统制备过程存在的毒性溶剂污染与安全问题，选择无毒且可生物降解的乳酸甲酯（ML）和碳酸丙烯酯（PC）作为绿色溶剂，借助非溶剂诱导相分离（NIPS）和热诱导相分离（TIPS）技术，在温和环境下成功制备了具有双层结构的聚偏氟乙烯（PVDF）超滤膜。通过汉森溶解度系数评估证实了ML/PC复合溶剂与PVDF的良好相容性，并利用凝胶转变温度测试确定了制膜过程的适宜温度范围。分析了绿色溶剂体系下超滤膜的形成过程及双层结构对膜性能的影响。结果表明，采用PVDF/ML/PC体系制备的支撑层疏松多孔，有利于水分子渗透运输；采用PVDF/ML体系制备的选择层结构致密，可提供良好的截留性能。二者复合构成的双层膜表面致密无缺陷，水接触角从108.27°降至79.75°，亲水性提升；膜截面呈双连续纤维交织状，力学性能优异，断裂伸长率高达481.8%。该超滤膜表现出优异的过滤能力，纯水通量高达2 006.0 L/（m²·h·MPa），牛血清白蛋白（BSA）截留率最高为99.9%，蛋白吸附量低于5.0×10^-5 g/cm²，为绿色溶剂制备高性能超滤膜提供了新途径。

关键词: 乳酸甲酯, 碳酸丙烯酯, 双层结构, 聚偏氟乙烯超滤膜

CLC Number:

TQ051.893

Manyao ZHU, Shujuan YANG, Bo JIANG, Yong ZHANG. Preparation and performance of bilayer polyvinylidene fluoride ultrafiltration membranes based on green solvents[J]. Industrial Water Treatment, 2026, 46(1): 105-113.

朱熳瑶, 杨淑娟, 蒋波, 张勇. 基于绿色溶剂的双层聚偏氟乙烯超滤膜的制备及其性能[J]. 工业水处理, 2026, 46(1): 105-113.

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URL: https://gyscl.magtechjournal.com/EN/10.19965/j.cnki.iwt.2025-0117

https://gyscl.magtechjournal.com/EN/Y2026/V46/I1/105

Figures/Tables 14

Fig.1 Preparation process of bilayer PVDF membrane

Table 1 Preparation parameters of PVDF ultrafiltration membranes with bilayer structure

膜	支撑层A刮刀厚度/μm	选择层B刮刀厚度/μm	支撑层暴露时间/min
A35-0	350	0	0
A35B-6M30	350	400	6.5
A45B-6M30	450	500	6.5
A40B-6M	400	450	6.0
A40B-6M30	400	450	6.5
A40B-7M	400	450	7.0
A40-6M	400	0	6.0
A40-6M30	400	0	6.5
A40-7M	400	0	7.0

Fig.2 Hansen solubility sphere radius （R ₀） and the position of a good and a bad solvent （R _a） for a specific polymer

Table 2 HEP for PVDF， green solvents， and traditional solvents

聚合物/溶剂混合物	δ _D/MPa^0.5	δ _P/MPa^0.5	δ _H/MPa^0.5	δ/MPa^0.5	R ₀	RED
PVDF	17.0	12.1	10.2	23.2	5.0
ML	15.5	7.2	7.6	18.7	6.3	1.3
PC	20.0	18.0	4.1	27.2	10.4	2.1
m（ML）∶m（PC）=43∶30	17.3	11.6	6.2	21.7	4.1	0.82
DMAC	17.8	14.1	11.8	25.6	3.0	0.60
NMP	18.0	12.3	7.2	23.0	3.6	0.72
DMF	17.4	13.7	11.3	24.9	2.1	0.42

Fig.3 Photographs of the gel state and film state

Fig.4 Photographs of bilayer membrane interlayer stability tests

Fig.5 XRD analysis of PVDF/ML/PC support layer （a） and bilayer film （b）

Fig.6 SEM images of support layers prepared at different exposure times （0，6，6.5，7 min）

Fig.7 SEM images of the magnified cross section

Fig.8 SEM images of bilayer-structured PVDF ultrafiltration membranes prepared with different exposure times and support layer thicknesses

Fig.9 Water contact angle dynamics of membranes

Fig.10 Membrane filtration performance

Fig.11 Mechanical properties of membranes

Fig.12 Summary data on mechanical properties of PVDF membranes prepared with green solvents

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