现代化工

现代化工 ›› 2026, Vol. 46 ›› Issue (2) : 116-121. DOI: 10.16606/j.cnki.issn0253-4320.2026.02.020

科研与开发

ZIF-8/PSF@Fe₃O₄-ZIF-8有机中空纤维复合膜的制备及其O₂/N₂分离性能研究

张如月 ¹ ,
苗泽凤 ¹ ,
刘聪聪 ² ,
杨腾飞 ¹^,^*

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Preparation of ZIF-8/PSF@Fe₃O₄-ZIF-8 organic hollow fiber composite membrane and study on its O₂/N₂ separation performance

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摘要

以磁性Fe₃O₄-ZIF-8核壳粒子作为填料,采用嵌入晶种法在PSF有机中空纤维上制备了ZIF-8/PSF@Fe₃O₄-ZIF-8复合膜,并对膜结构和O₂/N₂分离性能进行研究。结果表明,优化条件下PSF中空纤维表面制备了厚度为8.67 μm的连续 ZIF-8膜,其O₂渗透通量为3.52×10^-8 mol/(m²·s·Pa),O₂/N₂理想选择性为4.05。经过216 h运行和20次压力循环(0.1~0.2 MPa)测试,复合膜的O₂渗透通量以及O₂/N₂理想选择性基本保持恒定,表现出优异的长期运行稳定性和良好的制备重现性。相比掺杂纯ZIF-8晶种制备的有机中空纤维膜,ZIF-8/PSF@Fe₃O₄-ZIF-8有机中空纤维复合膜的O₂/N₂分离性能得到提升,证实磁性Fe₃O₄纳米粒子弱吸附和ZIF-8孔道筛分的协同增效作用。

Abstract

ZIF-8/PSF@Fe₃O₄-ZIF-8 composite membranes were prepared on PSF organic hollow fiber by a seed-embedded method using magnetic Fe₃O₄-ZIF-8 core-shell particles as fillers.The membrane structure and O₂/N₂ separation performance were systematically investigated.The results showed that a continuous ZIF-8 membrane with the thickness of 8.67 μm was prepared on the surface of PSF hollow fibers under the optimized conditions,with O₂ permeance of 3.52×10^-8 mol/(m²·s·Pa) and O₂/N₂ selectivity of 4.05.After 216 h of operation and 20 pressure cycles (0.1-0.2 MPa) tests,the O₂ permeance and O₂/N₂ selectivity of the composite membranes remained nearly unchanged,demonstrating good long-term operational stability and preparation reproducibility.The O₂/N₂ separation performance of ZIF-8/PSF@Fe₃O₄-ZIF-8 organic hollow fiber composite membranes was enhanced compared with that of organic hollow fiber membranes prepared by using pure ZIF-8 seeds as fillers,confirming the synergistic effects of the weak adsorption of magnetic Fe₃O₄ nanoparticles and the sieving of ZIF-8 pores.

Graphical abstract

关键词

Fe₃O₄-ZIF-8核壳粒子 / O₂/N₂分离 / 嵌入晶种法 / PSF有机中空纤维 / ZIF-8复合膜

Key words

Fe₃O₄-ZIF-8 core-shell particles / O₂/N₂ separation / seed-embedded method / PSF organic hollow fibers / ZIF-8 composite membranes

Author summay

张如月(1999-),女,硕士生,研究方向为传质与分离工程, 1528878195@qq.com。

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School of Chemistry and Chemical Engineering, Shandong University of Technology, Zibo 255000, China), AuthorCompanyExt(id=1241417717741220254, tenantId=1226480274814496768, journalId=1226484258170171394, articleId=1240720291778753450, companyId=1241417717728637340, language=CN, country=null, province=null, city=null, postcode=null, companyName=null, departmentName=null, remark=1.山东理工大学化学化工学院,山东淄博 255000)])])] 张如月,苗泽凤,刘聪聪,杨腾飞. ZIF-8/PSF@Fe₃O₄-ZIF-8有机中空纤维复合膜的制备及其O₂/N₂分离性能研究[J]. , 2026, 46(2): 116-121 DOI:10.16606/j.cnki.issn0253-4320.2026.02.020

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随着工业技术快速发展,O₂和N₂已成为现代工业中应用最广泛的工业气体^[1]。O₂应用于医疗、气化以及富氧燃烧等领域,N₂不仅是工业合成氨的原料,更常用作惰性气体^[2-6]。对于O₂和N₂分离,相比深冷精馏和变压吸附技术,膜分离技术具有设备投资少、能源消耗低、操作简便的优势,其中膜材料是气体分离技术的核心^[7-10]。聚合物膜材料是最常见的气体分离材料,但其通常存在渗透性与选择性之间的权衡效应问题^[11],开发具有优异O₂/N₂分离性能的新型膜材料成为研究热点。

ZIF-8是类沸石咪唑酯类骨架材料(ZIFs)系列中研究最为广泛的材料之一,理论孔径3.4 Å,与O₂动力学直径(0.34 nm)相近,这使其成为最有希望用于O₂/N₂分离的金属有机骨架(MOFs)材料^[12]。然而O₂与N₂的动力学直径相近,且O₂、N₂分子与常规膜材料之间缺乏特异性相互作用(如吸附或磁响应效应),导致分离选择性难以突破理论极限。近年来,磁性混合基质膜由于展现出特殊的O₂/N₂分离机制优势,通过巧妙地利用填充粒子和聚合物间的界面缺陷,在提高气体渗透性的同时增加了O₂/N₂选择性^[13]。通过在膜基质中引入纳米级磁体作为填料,可实现内部磁场的施加^[14]。康雪婷等^[15]采用溶剂挥发法在成膜过程中施加磁场制备了具有良好O₂/N₂分离性能的磁性膜。Rybak等^[16]在醋酸纤维素、聚酰亚胺等聚合物中掺入磁性钕颗粒,验证了磁性填料对分离性能的协同增强作用。尽管已有一些报道证明磁性能在一定程度上促进O₂/N₂分离,但过高掺杂量下磁性填料的团聚问题也不容忽视,此外现有磁性O₂/N₂分离膜大多局限于平板膜形式,对中空纤维膜的研究较少,难以发挥中空纤维膜的高比表面积、高传质效率和易集成组装优势^[17-19]。

采用嵌入晶种法,在掺杂磁性Fe₃O₄-ZIF-8核壳粒子的PSF有机中空纤维上,制备了共生性良好的ZIF-8膜。ZIF-8壳层的存在解决了Fe₃O₄纳米粒子易团聚的问题,同时,可作为异质成核位点促进晶体生长。该方法利用掺杂磁性Fe₃O₄纳米粒子的弱吸附作用与ZIF-8孔道筛分之间的协同作用,实现O₂渗透通量与O₂/N₂选择性的同时提升。

1 材料与试剂

1.1 试剂

聚砜(PSF),常州德毅新材料科技有限公司生产;四氧化三铁纳米粒子(Fe₃O₄ NPs),上海麦克林生化科技股份有限公司生产;聚乙烯吡咯烷酮(PVP),天津市光复精细化工研究所生产;六水合硝酸锌[Zn(NO₃)₂·6H₂O]、2-甲基咪唑(Hmim)、二水合甲酸钠(HCOONa·2H₂O)、N-甲基-2-吡咯烷酮(NMP)、无水甲醇(CH₃OH)、无水乙醇(C₂H₆O),国药集团化学试剂有限公司生产。巯基乙酸(MAA),上海迈瑞尔生化科技有限公司生产。

1.2 仪器

JJ-1型精密增力电动搅拌器,常州普天仪器制造有限公司生产;DHG-9055A型电热鼓风干燥箱,上海一恒科学仪器有限公司生产;HH-4恒温水浴锅,常州中捷实验仪器制造有限公司生产;7890B型气相色谱仪,安捷伦有限公司生产。

2 实验方法

2.1 Fe₃O₄-ZIF-8核壳粒子的制备

采用逐层包覆法在经MAA修饰的Fe₃O₄ NPs表面生长ZIF-8,制备得到Fe₃O₄-ZIF-8核壳粒子^[20-21]。将1 g Fe₃O₄ NPs分散到200 mL无水乙醇中,超声处理10 min后加入1 g MAA,在室温下搅拌24 h使其充分反应;反应结束后用磁铁分离产物并用新鲜甲醇充分冲洗;将改性后的Fe₃O₄ NPs重新分散到200 mL甲醇中待用。

向上述分散液中加入3 g Zn(NO₃)₂·6H₂O,超声处理10 min;待完全溶解后加入200 mL含有5.8 g Hmim的甲醇溶液,在50℃油浴条件下反应3 h;待反应结束冷却至室温后用磁铁分离产物,并用新鲜甲醇冲洗,在60℃真空干燥箱中干燥12 h得到Fe₃O₄-ZIF-8核壳粒子。通过重复上述步骤,可增加ZIF-8壳层的厚度,所得产物记为Fe₃O₄-ZIF-8-X(X为循环次数)。

2.2 PSF@Fe₃O₄-ZIF-8有机中空纤维的制备

称取25 g PSF、10 g PVP和75 g NMP置于250 mL烧杯中,使用电动搅拌器混合均匀;加入质量分数为15%的Fe₃O₄-ZIF-8-X核壳粒子;将铸膜液转移至不锈钢料桶中,真空处理1.5 h去除溶液中气泡;以m(NMP)∶m(CH₃CH₂OH)=2∶8的混合溶液为内凝固浴、去离子水为外凝固浴,通过相转化纺丝制备PSF@Fe₃O₄-ZIF-8有机中空纤维,在纯水中固化24 h后室温下晾干备用。

2.3 ZIF-8/PSF@Fe₃O₄-ZIF-8有机中空纤维复合膜的制备

将使用聚四氟乙烯带密封两端的PSF@Fe₃O₄-ZIF-8-X有机中空纤维置于含有摩尔比n[Zn(NO₃)₂·6H₂O]∶n(Hmim)∶n(HCOONa·2H₂O)∶n(CH₃OH)=1∶2∶0.65∶440^[22]合成液的高压釜中,在60℃下反应 8 h。反应结束后,将ZIF-8复合膜取出,用新鲜甲醇对膜层表面进行充分清洗,放入40℃真空干燥箱中烘干。制备过程如图1所示。

2.4 ZIF-8/PSF@Fe₃O₄-ZIF-8有机中空纤维复合膜的表征

采用场发射扫描电子显微镜(SEM)对膜样品的形貌和结构进行分析;采用日本Bruker D8 ADVANCE型X-射线衍射仪(XRD)对样品的晶体结构进行表征;采用透射电子显微镜(TEM)对晶体形貌进行观察并进行粒径分析;采用3H-2000TD-Y型孔隙率分析仪对中空纤维的孔隙率进行测试。

2.5 ZIF-8/PSF@Fe₃O₄-ZIF-8有机中空纤维复合膜的气体渗透性能测试

采用实验室自制的气体控压装置对膜样品的O₂和N₂进行单组分气体渗透性能测试,如图2所示。气体渗透量[P_i,mol/(m²·s·Pa)]与理想选择性(α_i/j)的计算公式如式(1)、式(2)所示:

(1)

P i = N i / (Δ P i A)

(2)

α O 2 / N 2 = P O 2 / P N 2

式中,N_i为i组分的摩尔渗透速率,mol/s;ΔP_i为膜层两侧的压力差,Pa;A为膜的有效面积,m²。

采用Wicke-Kallenbach分离模型对通过复合膜的双组分气体进行渗透性能测试,以CH₄作吹扫气,流速为40 mL/min,O₂和N₂的体积流量为 20 mL/min,通过质量流量计进行调节,并采用皂泡流量计对气体流量进行校准,混合气分离系数(S_i/j)的计算公式(3)为:

(3)

S O 2 / N 2 = (y O 2 / y N 2) / (x O 2 / x N 2)

式中,

x O 2

与

x N 2

分别为进料侧的摩尔分数,%;

y O 2

与

y N 2

分别为渗透侧的摩尔分数,%。

3 结果与讨论

3.1 Fe₃O₄-ZIF-8核壳粒子表征

MAA分子中的—COOH基团可以充当Fe₃O₄ NPs的表面修饰基团,在后续反应中能够与Zn²⁺络合,进而与Hmim配位,促进ZIF-8晶体层形成^[13]。基于此,采用MAA对Fe₃O₄ NPs进行表面改性,通过多次的ZIF-8生长循环,制备了以Fe₃O₄为核、ZIF-8为壳的Fe₃O₄-ZIF-8核壳粒子。Fe₃O₄-ZIF-8核壳结构的TEM表征如图3所示,未包覆Fe₃O₄ NPs的平均粒径约为12 nm,而经过3次ZIF-8生长循环后,颗粒粒径显著增加至约90 nm,证实ZIF-8在Fe₃O₄ NPs表面实现了有效包覆。Fe₃O₄ NPs及Fe₃O₄-ZIF-8核壳粒子的平均粒径均处于纳米尺度范围内,可显示出其原有的磁性,分散到PSF膜中形成磁性膜,对顺磁性O₂的传输具有一定促进作用^[23]。

在Fe₃O₄-ZIF-8核壳粒子的XRD图中(图4),2θ=35.5°处均出现Fe₃O₄的衍射峰,对应于(311)晶面,表明存在Fe₃O₄。其中,在7.3、10.4、12.7、14.7、16.4、18.3°处出现的衍射峰,分别与ZIF-8的(011)、(002)、(112)、(022)、(013)、(222)晶面相对应,与ZIF-8模拟衍射峰相匹配,证实ZIF-8的方纳石晶体结构在包覆过程中保持了完整性。此外,ZIF-8衍射峰强度随着循环次数的增加而不断增强,表明Fe₃O₄-ZIF-8核壳粒子的结晶度在提高。图4插图中显示制备的Fe₃O₄@ZIF-8核壳粒子在NMP中具有高分散性,并且可由磁铁吸引,证明该核壳粒子具有一定的磁性。Fe₃O₄-ZIF-8核壳结构的制备有效改善了Fe₃O₄ NPs的分散性,避免了高掺杂量下的团聚问题,同时为后续高性能ZIF-8复合膜的生长提供大量成核位点。

3.2 ZIF-8/PSF@Fe₃O₄-ZIF-8有机中空纤维复合膜

采用相转化法制备了PSF@Fe₃O₄-ZIF-8有机中空纤维,探究磁性Fe₃O₄-ZIF-8核壳粒子的引入对PSF有机中空纤维的O₂渗透性能的影响。以 m(NMP)∶m(CH₃CH₂OH)=2∶8的混合溶液为内凝固浴、去离子水为外凝固浴制备得到PSF有机中空纤维膜,其表面和截面SEM图见图5。膜截面呈现出典型的三明治状结构,两端为长而窄的指状孔,中间存在一层海绵层,具有较高孔隙率和较低传输阻力,是负载ZIF-8膜的理想载体。当循环次数为3次、Fe₃O₄-ZIF-8核壳粒子掺杂量为15%时,所得PSF@Fe₃O₄-ZIF-8有机中空纤维的孔隙率为85.69%,O₂渗透通量为1.47×10^-7 mol/(m²·s·Pa)。

载体表面存在的ZIF-8晶体不仅可作为膜生长的异质成核中心,而且在增强膜与载体的结合力方面起到关键作用^[24]。探究循环次数对膜性能的影响发现,Fe₃O₄-ZIF-8核壳粒子的总质量随着循环次数的增加而增加,并且3次循环后ZIF-8的质量占比由原先循环1次的44.96%增加至76.83%。ZIF-8壳层厚度及其在核壳粒子中占比的增加,可为后续膜的生长提供更多成核位点。图6为使用不同循环次数制备的PSF@Fe₃O₄-ZIF-8载体,于60℃、8 h条件下进行溶剂热合成制备ZIF-8复合膜的SEM图。仅1次循环时,所得膜表面存在缺陷,膜层厚度为2.33 μm[图6(a)],O₂/N₂理想选择性仅为2.23(图7)。这主要是由于载体表面上晶种数量越少,合成溶液中的结晶速率越高,导致可用于膜晶体生长的营养物质减少,最终只能形成较薄膜层^[25]。当循环次数增加至2次和3次时,载体表面ZIF-8晶种含量显著增加,异质成核密度增加,膜层厚度分别增加至6.67 μm和8.67 μm[图6(b)、(c)]。其中,当循环次数为3次时,制备ZIF-8复合膜的O₂渗透通量达到3.52×10^-8 mol/(m²·s·Pa),O₂/N₂理想选择性达到4.05(图7)。此外,在掺杂纯晶种的PSF@ZIF-8载体上经相同条件生长ZIF-8膜作为参照,由于载体表面晶种数量过多,生成的膜层厚度达到11.33 μm[图6(d)]。过厚的膜层增加了气体的传输阻力,O₂渗透通量仅为1.99×10^-8 mol/(m²·s·Pa),O₂/N₂理想选择性为3.01(图7)。上述对比表明掺杂Fe₃O₄-ZIF-8核壳粒子相比单纯ZIF-8晶种具有更好的控制成膜效果和气体筛分性能。

3.3 稳定性与制备重现性

膜的稳定性和制备重现性是评价其应用性能的关键指标。对ZIF-8/PSF@Fe₃O₄-ZIF-8复合膜在不同操作条件下的气体渗透性能进行了测试,结果见图8。图8(a)为不同操作压力下ZIF-8复合膜的气体渗透性能变化规律,由0.025 MPa到 0.2 MPa跨膜压力的改变并未引起单气体渗透通量的显著波动,说明制备的膜高度致密,未出现明显的缺陷或裂纹。进一步评估膜对压力波动的耐受性,在25℃条件下考察了0.1~0.2 MPa压力区间内O₂和N₂渗透性能的变化,如图8(b)所示。每个压力循环包含升压和降压两个过程[见图8(b)插图],经过20次循环测试后,0.1 MPa与0.2 MPa下的O₂和N₂渗透通量均保持稳定,证实制备的复合膜具有良好的压力波动耐受性。对于ZIF-8/PSF@Fe₃O₄-ZIF-8复合膜,进行分离等摩尔的O₂/N₂二元混合物的长期运行稳定性实验,在25℃下进行了216 h的连续测试,结果见图8(c)。在整个测试周期内,复合膜的气体渗透通量和O₂/N₂混合气分离系数几乎保持不变。最后,为验证制备方法的可重现性,在相同条件下制备了5个批次的ZIF-8/PSF@Fe₃O₄-ZIF-8复合膜,并对其进行了单气体渗透测试,结果如图8(d)所示。插图中数据表明,O₂和N₂的平均渗透通量分别为33.84、8.41×10^-9 mol/(m²·s·Pa),不同批次制备复合膜的气体渗透通量与平均值表现出高度一致性,表明该制备方法具有较好的制备重现性。

4 结论

采用嵌入晶种法成功制备ZIF-8/PSF@Fe₃O₄-ZIF-8有机中空纤维复合膜用于O₂/N₂分离,其中首先利用逐层包覆策略合成Fe₃O₄-ZIF-8核壳粒子,解决了Fe₃O₄ NPs易团聚问题,引入的ZIF-8壳层作为晶种也为后续膜层的生长提供了成核位点。磁性Fe₃O₄ NPs弱吸附作用与ZIF-8孔道筛分的协同作用使得复合膜表现出良好的O₂/N₂分离选择性(4.05)和优异的O₂渗透通量[3.52×10^-8 mol/(m²·s·Pa)]。ZIF-8/PSF@Fe₃O₄-ZIF-8中空纤维复合膜经过20个压力循环和216 h的长时间运行后仍保持了良好的O₂/N₂分离性能。该方法制备的复合膜具有优异的运行稳定性和制备重现性,为O₂/N₂分离膜合成提供了简单且有效的新策略。

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