水性聚氨酯膜渗透蒸发分离苯/环己烷的条件及过程

以聚己二酸1,4-丁二醇酯二醇(PBA-2000)和甲苯二异氰酸酯(TDI)为主要原料合成水性聚氨酯膜,并对苯/环己烷混合液渗透蒸发性能进行测试,讨论了苯/环己烷混合体系的渗透蒸发分离过程特点。结果表明,当膜厚度增大时,分离因子提高而渗透通量随之下降,这个变化趋势在膜较薄时很明显,达到一定厚度后则变化比较平缓;膜下游侧真空度提高会同时提高膜的分离因子和通量;增大料液中苯的浓度,提高料液温度会提高通量并降低分离因子。液体被分离组分在渗透蒸发膜中经历了吸附溶胀—膜内汽化—气体扩散的质量传递过程,"干区"对分离的影响作用更加显著。     

蒙脱石填充改性PDMS膜对稀溶液中苯的渗透分离性能

研究了CTAB柱撑改性蒙脱石填充聚二甲基硅氧烷(PDMS)膜对稀溶液中苯的渗透分离性能,考察了操作温度、有机蒙脱石填充量及料液中苯浓度对填充膜分离性能的影响. 结果表明,蒙脱石的填充不但能增强膜的机械性能,而且能明显改善膜的分离性能,随着蒙脱石填充量的增加,渗透通量增大,而分离因子先增大后减小;随着操作温度的提高,渗透通量明显增大,分离因子却减小;当料液中苯浓度增大时,苯通量增大,水通量保持不变,而分离因子减小. 用填充量为9.09%的填充膜对苯浓度为1000 kg/kg的料液进行渗透汽化实验,得到膜的渗透通量为115 g/(m2×h),分离因子达到798,比纯PDMS膜通量增大了12%,分离因子增大了32%.     

固载纳米银的聚酰亚胺混合基质膜的制备及其渗透汽化分离苯的性能

以AgNO_3为前驱体,利用浸渍吸附-热还原过程合成纳米Ag粒子-氧化石墨烯复合物,将该复合物通过共混法掺杂到聚酰亚胺高分子中,制备固载纳米银的聚酰亚胺混合基质膜,探索该膜在不同条件下对苯/环己烷混合物的渗透汽化分离性能。结果发现,热还原后得到的复合物中存在单质Ag,且Ag粒子良好地分散在氧化石墨烯表面。混合基质膜中Ag含量在15 wt%以内时,Ag粒子在膜中的分散性非常好,膜中没有出现明显的Ag粒子团聚物;当Ag含量超过20 wt%时,膜中出现了较为明显的Ag粒子团聚的形貌。在不同比例的苯/环己烷料液中,混合基质膜对料液渗透通量和分离因子的影响趋势总体相同。随着料液中苯质量分数的增加,膜的渗透通量也增加,分离因子则相反;随着温度的升高,膜的渗透通量也增高,分离因子则反之。     

新型渗透蒸发膜聚甲基双苯基硅氧烷膜的制备和分离

采用2种不同配方制备出苯基含量不同的聚甲基双苯基硅氧烷(PMPhS)膜并用于分离苯-水体系。接触角测定结果表明2种膜比PDMS膜亲苯疏水性增强。以渗透通量和分离因子为评价指标,研究了原料液温度、流动状况、质量分数、膜下游侧压力对渗透蒸发分离性能的影响,结果表明,随着原料液温度、流速以及料液浓度的提高,通量和分离因子都增加,随着下游侧压力的升高,通量和分离因子均降低。     

渗透蒸发膜分离有机双元混合物

本文以聚酰亚胺（ＰＩ）均质膜为渗透蒸发膜来分离苯和环己烷混合液，测定其渗透通量及透过液组成，证明ＰＩ膜对苯有极强的选择性；平衡溶解度大小影响着渗透通量的大小。在一定范围内，苯在ＰＩ膜内的扩散系数与其溶解度成指数关系，并将由此得到塑化因子ｒ，与苯和ＰＩ膜的相互作用参数的计算值进行了比较。同时，发现渗透通量、溶解度和扩散系数分别与温度之间符合Ａｒｒｅｈｅｎｉｕｓ方程。     

PDMS/PS复合膜的渗透蒸发性能的研究

制备了高性能的PDMS/PS复合膜,可将水溶液中苯的浓度由0.2～0.8×10-3kg·kg-1浓缩至70%～96%(质量分数),膜的渗透通量为0.10～0.4 kg·m-2·h-1,分离因子可达到20 000;通过渗透蒸发实验,考察了料液浓度、料液流速、料液温度和膜下游压力等操作条件对PDMS/PS复合膜渗透蒸发性能的影响;考察了活性层厚度和基膜结构分别对活性层传质阻力、基膜传质阻力的影响.并确定总传质阻力与活性层厚度的关系式和基膜传质阻力的经验公式.在此基础上得到了渗透蒸发的传质模型,计算结果与实验结果符合良好.     

二苯并-18-冠醚-6/聚醚嵌段酰胺膜富集水中苯酚性能研究

为提高聚醚嵌段酰胺 （PEBA）膜对水中苯酚的选择分离性能,采用二苯并-18-冠醚-6 (CE) 对PEBA膜进行改性制备了PEBA/CE渗透蒸发膜。通过FT-IR、SEM表征证实了CE与PEBA紧密结合且CE均匀分布在膜表面;AFM表征表明CE的修饰有效地提高了膜表面与苯酚的接触面积;水接触角测试表明CE的修饰极大地提高了PEBA/CE膜的疏水性。同时系统地研究了膜中CE含量、原料液苯酚浓度、进料温度对膜渗透汽化性能的影响,结果表明CE能显著提高PEBA膜对苯酚的选择性,在料液苯酚为0.8%（质量）及70℃操作温度条件下,当CE 的添加量为PEBA的6%（质量）时,PEBA/CE-6膜的分离因子和渗透通量分别为23.34和494.40 g/(m²·h),远超PEBA膜性能[分离因子8.46,总渗透通量547.48 g/(m²·h)]。长期性能稳定性测试表明所制备PEBA/CE-6膜具有良好稳定性,具有较好的工业运用潜力。     

壳聚糖-海藻酸钠/聚丙烯腈聚离子复合膜渗透汽化分离乙酸乙酯水溶液

制备了壳聚糖-海藻酸钠/聚丙烯腈（CS-SA/PAN）聚离子复合膜,将此膜用于渗透汽化分离乙酸乙酯水溶液.用红外光谱（FT-IR）表征CS、SA、CS/SA均质膜.研究CS-SA/PAN聚离子复合膜的溶胀性、料液浓度和SA质量分数、操作温度对乙酸乙酯水溶液脱水效果的影响.实验表明：CS/SA聚离子均质膜在乙酸乙酯水溶液中的溶胀度随溶液中水质量分数的增加而增大,随SA的质量分数增加而减小,40℃、SA质量分数为2.0%时,CS/SA聚离子均质膜在乙酸乙酯质量分数为97%的水溶液中溶胀度可达51%.随着SA质量分数的增加,CS-SA/PAN聚离子复合膜的渗透通量减小,分离因子增大,40℃、SA质量分数为2.0%时,分离乙酸乙酯质量分数为97%的水溶液,CS-SA/PAN聚离子复合膜渗透通量可达348g/（m^2.h）,分离因子为7245.随着料液中水含量的增加和料液温度的升高,膜渗透通量增大,分离系数减小,渗透通量与料液温度的关系能较好地吻合Arrhenius方程.     

渗透蒸发过程脱除水溶液中挥发性有机物的研究

采用自制的PDMS膜研究了从VOCs (挥发性有机化合物 )稀水溶液中脱除VOCs的渗透蒸发过程。以分离因子和渗透通量为评价指标 ,考察了料液浓度、温度和流动状况以及膜下游压力对膜的渗透蒸发分离性能的影响 ;并研究了针对脱除水溶液中VOCs的渗透蒸发过程的传质模型。     

用于芳烃/烷烃体系蒸汽渗透分离的离子液体支撑液膜研究

研究离子液体"填充型"支撑液膜制备规律,以及操作条件对苯/环己烷混合物蒸汽渗透分离过程影响。利用[C4mim][BF4]、[C8mim][BF4]、[C4mim][PF6]、[C6mim][PF6]、[4-Mebupy][BF4]、[3-Mebupy][BF4]离子液体分别制备支撑液膜,用于苯/环己烷混合物蒸汽渗透膜分离过程研究。实验比较了离子液体的种类、操作温度、原料液浓度等因素对苯/环己烷混合体系的蒸汽渗透膜分离性能的影响,其中[3-Mebupy][BF4]制得的支撑液膜对等体积配比的苯和环己烷混合物分离效果最佳,30℃时渗透通量为11.4g?m2?h?1,分离因子可达32.85。通过长时间运行的稳定性实验,证实离子液体支撑液膜的蒸汽渗透过程能够实现苯和环己烷的有效分离,具备良好的稳定性。离子液体"填充型"支撑液膜有望成为降低芳烃/烷烃等有机溶剂体系分离过程能耗的有效途径。     

Pervaporative separation of butanol using a composite PDMS/PEI hollow fiber membrane

In the study, the separation and purification of butanol was carried out using the composite hollow fiber membrane having the active layer of polydimethylsiloxane (PDMS) on the macroporous support of polyetherimide (PEI). The pervaporation results with the initial butanol concentration showed a trade-off between flux and separation factor. However, both the flux and the separation factor increased as the operating temperature increased. The pervaporation results showed the butanol flux and the separation factor were higher than those of the reported results. In this study, butanol was concentrated by the pervaporation as a feasibility study for the biofuel applications.     

聚丙烯酸-聚乙烯醇共混膜分离甲醇-碳酸二甲酯共沸体系

采用涂敷法制备了聚丙烯酸(PAA)-聚乙烯醇(PVA)共混膜,将其用于渗透汽化法分离甲醇(MeOH)-碳酸二甲酯(DMC)共沸物,考察了共混比例、热处理条件对甲醇分离性能的影响. 渗透汽化实验结果表明,随着热处理时间延长或热处理温度提高,分离因子先升高后降低,而渗透通量则逐渐减小;随着共混膜中PAA/PVA比例增加,分离因子先升高后降低,而渗透通量先减小后增大;当PAA/PVA质量比为7/3、热处理时间为60 min、热处理温度为150℃时,选择性最佳,在料液组成为70%(w) MeOH-30%(w) DMC及70℃的操作温度下,甲醇的分离因子为9.5(透过侧MeOH浓度为95.5%, w),渗透通量为360 g/(m2×h).     

Characterization of sodium alginate and poly(vinyl alcohol) blend membranes in pervaporation separation

By blending a rigid polymer, sodium alginate (SA), and a flexible polymer, poly(vinyl alcohol) (PVA), SA/PVA blend membranes were prepared for the pervaporation separation of ethanol–water mixtures. The rigid SA membrane showed a serious decline in flux and a increase in separation factor due to the relaxation of polymeric chains, whereas the flexible PVA membrane kept consistent membrane performance during pervaporation. Compared with the nascent SA membrane, all of the blend membranes prepared could have an enhanced membrane mobility by which the relaxation during pervaporation operation could be reduced. From the pervaporation separation of the ethanol–water mixtures along with the temperature range of 50–80°C, the effects of operating temperature and PVA content in membrane were investigated on membrane performance, as well as the extent of the relaxation. The morphology of the blend membrane was observed with PVA content by a scanning electron microscopy. The relaxational phenomena during pervaporation were also elucidated through an analysis on experimental data of membrane performance measured by repeating the operation in the given temperature range. SA/PVA blend membrane with 10 wt % of PVA content was crosslinked with glutaraldehyde to enhance membrane stability in water, and the result of pervaporation separation of an ethanol–water mixture through the membrane was discussed. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:949–959, 1998     

Preparation and Characterization of Silicone Rubber Membrane

Pervaporation membrane with preferential permeation for organic compounds over water was prepared and characterized. Selection of membrane material and the effects of polydimethylsiloxane (PDMS), cross-linker, and catalyst concentrations on performances of pervaporation membrane at room temperature were discussed. In addition, the time of cross-linking, and the kinds of basic plate in the process of preparation were tested. The formulation of pervaporation membrane material was determined. Through the characterization of membrane by infrared spectrometry(IR), scanning electron microscopy(SEM), transmission electron microscopy(TEM) and X-ray diffraction(XRD), it is proved that the structures and characters are suitable for the pervaporation process. Experiments also demonstrate that the permeate flux and separation factor are suitable for the process.     

Characterization of relaxation phenomena and permeation behaviors in sodium alginate membrane during pervaporation separation of ethanol–water mixture

The pervaporation separation of a concentrated ethanol–water mixture with 90 wt % of ethanol content through a sodium alginate (SA) membrane was carried out to investigate both the relaxation process and permeation behavior of the membrane in pervaporation. From the swelling measurement of the membrane in 90 wt % of ethanol content of the aqueous solution, it was observed that SA has an excellent permselectivity toward water and a high solubility of water: about 1000 of sorption selectivity and 21 wt % of water content in the swollen membrane at 40°C. Its excellent sorption properties could result in the outstanding pervaporation performance for the aqueous solution; higher than 10,000 of separation factors and 120–290 g/(m²h) of fluxes, depending on the operating temperature. However, a serious flux decline took place with operating time due to the occurrence of a significant relaxation process in SA. The flux decline was remarkable at the beginning stage and then mitigated with operating time. The fluxes were reduced by about 40–50% because of the relaxation process during the measurement. To analyze these phenomena in more detail, the hysteresis behavior of membrane performance along with an operation temperature cycle was investigated. During the heating process in the cycle, the relaxation process was important to affect membrane performance while the formation of excess stress in the membrane might be a crucial factor during the cooling process. It was postulated from the experimental observations that in the heating process an increase in flux with temperature is restricted by a more rapid relaxation process at a higher operation temperature, while in the cooling process, the excess stresses in the membrane are formed and accumulated in and near the transition zone and near the area in the membrane because of slower relaxational consolidation in unequilibrium cooling than in relaxational dilation in the heating process, resulting in flux more sensitive to temperature than in the heating process. These phenomena were found diminished as the relaxation time increased with aging time. The relaxation phenomena were discussed through an analysis on permeation activation energy data obtained from the pervaporation experiments. A qualitative model was established to describe the relaxation phenomena in the membrane material during the pervaporation process by using the basic principles of polymeric relaxation and the experimental observations obtained in this study. © 1996 John Wiley & Sons, Inc.     

有机硅烷改性ZSM-5/BPPO非对称膜制备及其渗透汽化性能

以硅烷改性ZSM-5分子筛为填充剂,采用沉浸凝胶相转化法制备了ZSM-5/BPPO非对称膜. 结果表明,分子筛在BPPO膜中分散均匀,填充分子筛后膜表面粗糙度增大、疏水性增强. 以低浓度乙醇-水体系为研究对象,考察了分子筛填充量、进料液浓度及进料液温度对ZSM-5/BPPO膜渗透汽化分离性能的影响. 结果表明,随乙醇浓度增大,ZSM-5/BPPO膜的分离因子减小,渗透通量增大;随进料液温度升高,ZSM-5/BPPO膜的分离因子及渗透通量均增大;在60℃、分子筛填充量为0.3%(w)时,ZSM-5/BPPO膜对5%(w)乙醇-水体系的分离因子高达18.49,渗透通量为529.69 g/(m2×h). ZSM-5/BPPO膜对不同醇-水体系的分离结果表明,醇类分子量越大,膜分离性能越好.     

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.     

Effect of operation conditions in the pervaporation of ethanol–water mixtures with poly(1‐trimethylsilyl‐1‐propyne) membranes

Poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) is known to show preferential permeation of ethanol in the pervaporation of ethanol–water mixture. Although this polymer presents good characteristics for the separation of organic–water solutions, operation conditions and membrane characteristics, such as thickness, affect its pervaporation performance. The effect of temperature and feed concentration on pervaporation was studied. During pervaporation of 10 wt % ethanol–water solution, the separation factor (α_H2O^EtOH) remains almost constant, whereas the permeation flux (F) increases exponentially with operation temperature. On the other hand, the separation factor decreases, whereas the permeation flux increases with ethanol content in the feed mixture. The membrane thickness also affects the performance of PTMSP polymer films: selectivity increases sharply with membrane thickness up to 50 μm, whereas it remains constant for thicker membranes. The permeation flux decreases with membrane thickness in the whole range studied. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94:1395–1403, 2004     

丙炔醇-丁炔二醇-水溶液的渗透汽化分离研究

用PDMS复合膜从实际的丙炔醇-丁炔二醇-水溶液中渗透汽化分离丙炔醇。实验证明,膜渗透汽化可以实现丙炔醇的选择性分离,对水的分离因子可达3.78;丁炔二醇被膜完全截留;丙炔醇通量对温度具有敏感性,通量随着温度的增加上升得很快,丙炔醇通量在25℃时为45.28g/(m2.h),在60℃时为243.24g/(m2.h),显示了PDMS膜从这个体系中分离丙炔醇具有某种优势;对实验数据进行线性回归,证明丙炔醇通量和温度的关系可以用Arrhenius公式表征。为工业上用PDMS膜渗透汽化分离提纯丙炔醇提供参考。