PDMS/ZSM-5膜的制备及渗透汽化分离水中乙酸正丁酯和乙酸乙酯

为探究出适合分离水中的乙酸正丁酯和乙酸乙酯的新型渗透汽化膜材料,选用沸石ZSM-5 对聚二甲基硅氧烷(PDMS)材料进行填充改性,以聚偏氟乙烯(PVDF)为支撑层,采用刮涂法制备PDMS/ZSM-5/PVDF复合膜渗透汽化分离水中的乙酸正丁酯和乙酸乙酯。采用SEM、接触角测量仪、FTIR、TGA和XRD等对膜材料物理化学性能进行表征,考察了膜材料的溶胀行为及渗透汽化性能。结果表明,ZSM-5在 PDMS 膜中分散均匀,且没有发生化学作用,并提高了膜材料的疏水性和热稳定性。随着ZSM-5添加量的增加,膜在乙酸正丁酯和乙酸乙酯的溶胀度和待分离组分在膜材料中的扩散速率不断增加。随着进料浓度和温度的增加,渗透通量不断增大,分离因子先增大后减小。随着ZSM-5在PDMS/ZSM-5/PVDF复合膜中含量的增加,总渗透通量增加,而分离因子呈现先增加后减小的趋势。当添加量为10%（质量）时,分离因子达到最大值。对于乙酸正丁酯/水体系,渗透通量和分离因子最大值分别为319 g·m ^-2·h ^-1和131;而对于乙酸乙酯/水体系,渗透通量和分离因子最大值分别为1385 g·m ^-2·h ^-1和121。     

无机盐对聚二甲基硅氧烷/陶瓷复合膜渗透汽化性能的影响

将渗透汽化应用于醇/水体系的分离,具有诸多显著的优势。然而,目前的研究大都基于二元体系,而实际的应用体系是多元的,还包含少量无机盐和糖类等,它们的存在对膜的性能具有一定的影响。本文研究了NaCl、KCl和MgCl2 3种无机盐的加入对聚二甲基硅氧烷 （PDMS）/陶瓷复合膜渗透汽化性能的影响。结果表明,在313 K,无机盐的加入使复合膜的分离因子和通量均有所提高。其中二价盐MgCl2对渗透汽化性能的影响最为显著,分离因子最大提高到醇/水体系的2.8倍。而一价盐NaCl和KCl的加入,使分离因子分别提高为醇/水体系的2.5倍和2.4倍。同时借助于Setschenow扩展方程计算了乙醇活度,对实验结果进行了初步的解释。     

有机硅烷交联PDMS/陶瓷复合膜的制备及渗透汽化汽油脱硫性能

采用有机硅烷γ-氨丙基三甲氧基硅氧烷（APTMS）,对聚二甲基硅氧烷（PDMS）进行交联改性,以ZrO₂/Al₂O₃陶瓷复合膜为支撑体,制备了一系列有机硅烷交联的PDMS/陶瓷复合膜。通过扫描电镜（SEM）、傅里叶红外光谱（FTIR）、热重分析（TGA）对改性效果和膜结构进行了表征。将所制备的PDMS/陶瓷复合膜应用于渗透汽化脱除模拟汽油中的有机硫化物（噻吩）,考察了交联剂APTMS含量、操作温度、料液含硫量等因素对复合膜渗透汽化脱硫性能的影响。实验结果表明,有机硅烷交联的PDMS膜相比于传统正硅酸乙酯（TEOS）交联的PDMS膜,通量和硫富集因子均有所提高。随着进料温度和原料液中硫含量的升高,膜的渗透通量均增大,而硫富集因子均减小。当APTMS质量分数为15%、进料温度为25℃、噻吩质量浓度为100mg/kg时,渗透通量为0.46 kg/（m²·h）,硫富集因子达到3.5。     

疏水SiO2填充PDMS膜分离水中乙酸正丁酯的性能

以聚偏氟乙烯（PVDF）为支撑层,选用疏水性纳米SiO₂粉体作为改性剂,制备出聚二甲基硅氧烷（PDMS）复合膜材料,并用于乙酸正丁酯/水溶液的渗透汽化分离。采用SEM、FTIR、XRD、拉伸实验、接触角及正电子湮没寿命谱测定等对膜材料物理化学性能进行了表征,考察了膜材料的溶胀行为及渗透汽化性能。结果表明,SiO₂在PDMS膜中分散均匀,且没有发生化学作用,并提高了膜材料的机械强度和疏水性。随着SiO₂添加量增加,膜在乙酸正丁酯溶液中的溶胀度先升后降,渗透通量呈下降趋势,而分离因子先增大后减小。当SiO₂添加量为4%（质量）时,随进料浓度的增加,渗透通量增大,分离因子先增大后减小;随着温度升高,渗透通量增大,分离因子减小;渗透通量和分离因子最大值分别为240 g·m^-2·h^-1和542。     

聚偏氟乙烯/聚二甲基硅氧烷渗透气化膜在丁醇分离中的应用

通过相转化法制备PVDF多孔支撑膜,在其上涂覆致密的PDMS分离层制备得到PVDF/PDMS复合膜,用于丁醇的分离纯化。以丁醇水溶液为原料液,流速为1.6 L·min^-1,丁醇浓度为15 g·L^-1,温度为37℃时, PVDF/PDMS复合膜的总通量为158.2 g·m^-2·h^-1,分离因子为17.3。向丁醇水溶液中按丁醇：丙酮：乙醇比例为6：3：1添加丙酮和乙醇模拟发酵液,PVDF/PDMS复合膜的总通量升高到189.5 g·m^-2·h^-1,分离因子降低到14.8。进一步考察了以丙酮-丁醇-乙醇（ABE）发酵液为原料液的渗透气化膜分离性能,发酵液中不存在菌体时,PVDF/PDMS复合膜的总通量和分离因子分别为120.2 g·m^-2·h^-1和19.7,而菌体存在时,复合膜的总通量和分离因子分别为122.1 g·m^-2·h^-1和16.7。与PDMS均质膜相比,PVDF/PDMS复合膜在丁醇分离过程中的分离性能有了显著的提升, 具有潜在的应用价值。     

ZIF-L/PDMS混合基质膜蒸气渗透耦合发酵强化乙醇生产效率的研究

蒸气渗透（VP）膜分离不存在膜污染风险,在生物乙醇生产中具有广阔的应用前景。将聚二甲基硅氧烷（PDMS）膜和以二维沸石咪唑骨架（ZIF-L）为填充基质制备的PDMS（ZIF-L/PDMS）混合基质膜,分别用于VP膜分离与菊粉水解液发酵制乙醇过程的耦合,分析了二者在耦合过程中的分离性能和发酵性能。探究了不同膜分离方式、不同类型膜及操作条件对膜分离性能的影响。实验结果表明,当料液浓度为5%（质量）、蒸气循环流量为1.5 L·min^-1时,ZIF-L/PDMS混合基质膜的VP性能高于渗透汽化（PV）,归一化总通量达到1148.78 g·m^-2·h^-1,分离因子高达19.14,显著提升了乙醇分离性能。ZIF-L/PDMS混合基质膜用于VP耦合发酵,实现了耦合过程的高渗透性和乙醇选择性,与文献报道相比,乙醇移除效果最优,乙醇产率和时空产率分别达到0.421 g·g^-1、3.07 g·L^-1·h^-1,两个指标明显高于单独发酵,极大地提高了乙醇生产效率。因此,ZIF-L/PDMS混合基质膜在原位分离发酵乙醇方面具有很大的应用潜力。     

聚偏氟乙烯/聚二甲基硅氧烷渗透气化膜在丁醇分离中的应用

通过相转化法制备PVDF多孔支撑膜,在其上涂覆致密的PDMS分离层制备得到PVDF/PDMS复合膜,用于丁醇的分离纯化。以丁醇水溶液为原料液,流速为1.6 L·min-1,丁醇浓度为15 g·L-1,温度为37℃时,PVDF/PDMS复合膜的总通量为158.2 g·m-2·h-1,分离因子为17.3。向丁醇水溶液中按丁醇:丙酮:乙醇比例为6:3:1添加丙酮和乙醇模拟发酵液,PVDF/PDMS复合膜的总通量升高到189.5 g·m-2·h-1,分离因子降低到14.8。进一步考察了以丙酮-丁醇-乙醇(ABE)发酵液为原料液的渗透气化膜分离性能,发酵液中不存在菌体时,PVDF/PDMS复合膜的总通量和分离因子分别为120.2 g·m-2·h-1和19.7,而菌体存在时,复合膜的总通量和分离因子分别为122.1 g·m-2·h-1和16.7。与PDMS均质膜相比,PVDF/PDMS复合膜在丁醇分离过程中的分离性能有了显著的提升,具有潜在的应用价值。     

碳纳米管填充PDMS膜的渗透汽化性能

将碳纳米管（CNTs）填充到PDMS中制备出CNTs/PDMS杂化膜,并将其用于乙醇/水体系的分离,发现由多壁碳纳米管制备的膜分离性能优于单壁碳纳米管填充膜,在40℃下,进料乙醇浓度为5%（质量分数）时,膜的分离因子可由8.3提高到10.0,渗透通量为206.2 g·（m²·h）^-1;采用十二烷基三氯硅烷对多壁碳纳米管进行修饰,并对修饰前后碳纳米管的性能进行表征,研究表明修饰后碳纳米管表面形成疏水层,碳纳米管的疏水性增强;将修饰后的碳纳米管填充到PDMS中,可进一步提高杂化膜对乙醇的选择性,膜的分离因子可提高到11.3,渗透通量为130.9 g·（m²·h）^-1。     

纳米白炭黑填充硅橡胶复合膜的制备与渗透汽化分离性能

制备以聚酯(PET)为支撑层,白炭黑填充的聚二甲基硅氧烷(PDMS107)为皮层的硅橡胶复合膜,并以乙醇水物系为料液,对比分析白炭黑增强硅橡胶复合膜的渗透蒸发分离性能,分离因子比空白膜有所提高,在乙醇浓度为3%～5%时,分离因子可达16.09,渗透通量为75.39 g/m2·h;测定填充白炭黑硅橡胶复合膜的拉伸强度,结果表明:拉伸强度可达1.828 MPa,相当于空白膜(0.368 MPa)的5倍.     

PDMS涂覆的Al2O3中空纤维膜在ABE/水体系分离中的应用

通过浸渍-提拉的方法制备了PDMS涂覆的Al2O3中空纤维膜,并系统地研究了其用于ABE/水体系的分离过程。首先对制备出的膜进行了形貌表征,SEM电镜照片表明,所用的Al2O3中空纤维支撑体具有非对称结构,海绵孔位于膜壁的中间而指状孔在其两侧。制备出的PDMS涂覆的Al2O3中空纤维复合膜表面致密完好没有缺陷,其厚度小于10μm,说明PDMS层被均匀地涂在支撑体外表面。然后在不同的模拟体系(丙酮-水、丁醇-水、乙醇-水)中,系统地考察了复合膜的性能。实验表明,复合膜具有优异的渗透汽化性能(通量和分离因子)。最后将该复合膜用于ABE-水体系的分离,考察了膜在操作过程中的渗透汽化性能和稳定性,同时将二元体系与四元体系过程对比,讨论渗透汽化对ABE体系的分离作用。     

Liquid–liquid interface induced PDMS-PTFE composite membrane for ethanol perm-selective pervaporation

Pervaporation has great potential in the separation of many significant mixtures. However, excessive penetration of separation layer into the substrate pores enhances the transport resistance of solvent molecules, which impedes the development of pervaporation membrane. In this study, a facile floating-on-water (FOW) method was used to prepare poly(dimethylsiloxane) (PDMS)/polytetrafluoroethylene (PTFE) composite membranes. The formation of separation layer and preparation of composite membrane were step-by-step completed through this liquid–liquid interface induced method. The PDMS layer thickness could be precisely regulated from 0.5 to 8 μm. Moreover, the pore penetration could be controlled by optimizing pre-crosslinking density, crosslinking time on water and polymer solution volume. The obtained PDMS/PTFE composite membrane exhibited a high flux of 2016 g·m⁻²·h⁻¹ with the separation factor of 12 when separating ethanol from a 5 wt% ethanol/water mixture. The performance of the membrane could be stable for over 200 h, exhibiting great potential in ethanol perm-selective pervaporation.     

Simultaneously enhancing interfacial adhesion and pervaporation separation performance of PDMS/ceramic composite membrane via a facile substrate surface grafting approach

A facile substrate surface silane-grafting approach was demonstrated to enhance both interfacial adhesion and pervaporation separation performance of PDMS composite membrane. With C₁₆ grafted ceramic substrate, the PDMS/ceramic composite membrane exhibited up to 1.7 times stronger interfacial adhesion force between separation layer and substrate layer, meanwhile 1.5 times larger butanol/water separation factor that is higher than state-of-the-art membranes. This novel approach paves a new avenue to developing composite membranes with high and stable separation performance.     

PTFE对PDMS复合膜在低浓度有机物水溶液中渗透汽化性能的影响

制备了聚四氟乙烯（PTFE）超细粉体填充聚二甲基硅氧烷（PDMS）复合膜,通过扫描电子显微镜、傅里叶变换红外光谱仪、热失重分析仪等测试仪器对复合膜进行了表征,利用低浓度有机物（乙醇、丙酮、正丙醇）水溶液体系进行渗透汽化,并由单组分溶解实验计算了有机物（乙醇、丙酮、正丙醇）在复合膜中的溶解度。结果表明,PTFE含量由0增加至10 %（质量分数,下同）时, 复合膜的表面积及热稳定性得到了提高,有机物乙醇、丙酮、正丙醇在复合膜中的溶解度分别由0.0923、0.1589和0.2691 g/g提高至0.0991、0.1678和0.2773 g/g;加入PTFE后提高了复合膜的渗透汽化性能。     

Spray-coated PDMS/PVDF composite membrane for enhanced butanol recovery by pervaporation

In this study, spray-coating was used to prepare dihydroxypolydimethylsiloxane (PDMS) composite membranes with high flux and separation factor for biobutanol recovery from aqueous solution. A thin, smooth, and defect-free PDMS layer was prepared by spray-coating on polyvinylidene difluoride ultrafiltration membrane with little PDMS penetration. The effects of process parameters for membrane fabrication and pervaporation on membrane performance were investigated. A membrane with 2 μm active layer was obtained with a high flux of 1306.9 g/m² h. The optimal membrane with the highest pervaporation separation index (PSI) (19.15 kg/m² h) showed a total flux of 530.6 g/m² h and a separation factor of 36.1 at 37°C, and a PSI of 65.61 kg/m² h and a flux of 1927.0 g/m² h at 70°C. Membrane performance was affected by feed composition and temperature. Acetone-butanol-ethanol solution and fermentation broth gave lower butanol fluxes and separation factors compared to butanol model solution.     

Preparation and characterization of Silicalite‐1/PDMS surface sieving pervaporation membrane for separation of ethanol/water mixture

To improve the pervaporation performance of Silicalite‐1/PDMS composite membrane by adding a small amount of Silicalite‐1 zeolite, novel Silicalite‐1/PDMS surface sieving membranes (SSMs) were prepared by attaching Silicalite‐1 particles on the PDMS membrane surface. The obtained membranes and traditional mixed‐matrix membranes (MMMs) were characterized by SEM, XRD, TGA, FT‐IR, and pervaporation separation of ethanol–water mixture. Effects of Silicalite‐1 particles content, feed temperatures, and feed compositions on the separation performance were discussed. From the cross‐section view SEM images of SSMs, a two‐layer structure was observed. The thickness of the Silicalite‐1 layer was about 300 nm to 2 μm. The TGA analysis indicates that the zeolite concentration in 3 wt % SSM is lower than 10 wt % MMMs. In the ethanol/water pervaporation experiment, the separation factor of Silicalite‐1/PDMS SSMs increased considerably compared with pure PDMS membrane. When the suspensions concentrations of Silicalite‐1 particles reached 3 wt %, the separation factor was about 217% increase over pure PDMS membrane and 52.9% increase over 10 wt % Silicalite‐1/PDMS MMMs. As the ethanol concentration in the feed increases, the separation factor of SSMs increases, whereas permeation flux decreases. At the same time, with increasing operating temperature, the permeation flux of SSMs increased. The stability of SSMs at high temperature is better than the traditional MMMs. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42460.     

PDMS/ceramic composite membrane for pervaporation separation of acetone–butanol–ethanol (ABE) aqueous solutions and its application in intensification of ABE fermentation process

Pervaporation (PV) has attracted increasing attention because of its potential application in bio-butanol recovery from fermentation process. In this work, PDMS/ceramic composite membrane was employed for PV separation of acetone–butanol–ethanol (ABE) aqueous solutions. The influence of coupling effect on the molecular transport during the PV process was systematically investigated. The separation performance and transport phenomena of ABE molecules were discussed based on the analysis and calculation of physicochemical properties such as solubility parameter, polarity parameter, interaction parameter, activity coefficient. The results suggested that the ABE separation factor was mainly determined by the intrinsic solubility parameter and driving force. Coupling effect in the ABE multicomponent system was closely related to the interaction parameters between components themselves and between component and membrane. Also, the PDMS membrane was integrated with ABE fermentation to construct an efficient intensification process. It was found that the rate matching of fermentation and in situ removal could improve the ABE productivity by 2 times.