Water–alcohol separation by pervaporation through poly(amide-sulfonamide)s (PASAs) membranes

Pervaporation membranes derived from seven homopolymers of poly(amide-sulfonamide)s (PASAs) were prepared by casting 10–17% polymer solutions of N,N-dimethylacetamide. The membranes were characterized by sorption experiments, scanning electron microscope, and wide-angle X-ray diffraction. During the pervaporation of 90 wt % aqueous solution of methanol, ethanol, 1-propanol, and 2-propanol, all membranes were preferentially permeable to water, and their separation factors were mainly dependent on the molecular weight of the solvent. The exact structure of the PASAs had a profound effect on their pervaporation characteristics. Polymeric membrane based on N,N′-bis(4-aminophenylsulfonyl)-1,3-diaminopropane and isophthaloyl chloride exhibited the best selectivity factor of 1984 for a 10 : 90 (by weight) mixture of water/ethanol at 20°C. However, the permeation rates of all materials for dehydration of 90 wt % ethanol were slow in a range of 6.6–34.4 g m⁻² h⁻¹. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1113–1119, 1997     

Processing of liquid propellant reaction liquors by pervaporation

Unsymmetrical dimethylhydrazine and monomethylhydrazine are the two well‐known liquid propellants. Substantial amounts of sodium chloride present in the aqueous unsymmetrical dimethylhydrazine and monomethylhydrazine reaction liquors. Pervaporation experiments have been conducted using dense chitosan membrane for desalting of these reaction liquors. The effect of membrane thickness, salt concentration in the feed, and permeate pressures on flux and % rejection have been studied and discussed to optimize the conditions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 141–149, 1999     

Pervaporation separation of styrene–ethylbenzene mixture using poly(hexamethylene sebacate)‐based polyurethane membranes

A series of poly(hexamethylene sebacate) (PHS), with molecular weight in a range of 890–2200, based polyurethanes (PU), were synthesized by solution polymerization with different kinds of isocyanate and chain extender and two kinds of polymerization methods. All the PHS‐based PU membranes exhibited selectivity towards styrene during the pervaporation of styrene–ethylbenzene mixtures, and the properties of sorption and pervaporation were related to the composition of the PU membranes. Membranes with a low hard‐segment content and by two‐stage polymerization method exhibited high permselectivity. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 753–761, 1999     

Application of surface modifying macromolecules in polyethersulfone membranes: Influence on PES surface chemistry and physical properties

Novel surface modifying macromolecules (SMMs) were developed for incorporation into polyethersulfone (PES) membranes, intended for pervaporation applications. These materials were synthesized with a diisocyanate, polypropylene oxide (PPO), and a fluoro-alcohol, and characterized for elemental analysis, molecular weight, and glass transition temperatures. PES/SMM blends with eight types of SMMs were characterized for surface and physical properties and compared with PES. Water droplet contact angle measurements and X-ray photoelectron spectroscopy data showed that the SMMs migrated to the surface and rendered the PES material more hydrophobic. While advancing contact angle data were equivalent to those of pure Teflon™, the highest average values of receding angles of these systems were less than those of commercial Teflon™. The opaqueness of PES/SMMs films and data from differential scanning calorimetry experiments showed that the SMMs were either immiscible or only partially miscible with PES. It was also observed, for a fixed PES concentration of 25 wt %, that increases in the molecular weight of the SMMs and the weight fraction of PPO in the SMMs led to phase separation in the ternary PES/SMMs/dimethylacetamide (i.e., membrane casting solution) system. On the other hand, in the binary PES/SMMs system (i.e., cast membrane film), an increasing weight fraction of fluorine in the SMMs contributed to an increase in the phase separation. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1363–1378, 1999     

Removal of N‐butanol from aqueous solutions by ion–exchange membranes containing organic counterions

The pervaporation of aqueous butanol solutions was investigated using thin‐film composite membranes composed of a poly(vinylidene fluoride) substrate coated with a sulfonated poly(2,6‐dimethyl‐1,4‐phenelene oxide) polymer. The polymer was ion‐exchanged with quaternary ammonium cations having aliphatic substituents of various chain lengths. The pervaporation of aqueous n‐butanol solutions using these membranes gave a permeate more concentrated in n‐butanol; therefore, they were alcohol‐selective. The separation factor increased and the permeate flux decreased as the chain lengths of the aliphatic substituents were increased. Hence, the mass‐transport properties of such membranes can be controlled or altered to yield some desired permselectivity by the introduction of a proper counterion. It was observed that the n‐butanol flux was small relative to the total flux and, therefore, the water flux dominated the total permeate flux. The degree of swelling of the membranes and its effect on membrane performance was investigated as well. As the n‐butanol content was increased, the swelling of the membranes increased greatly. High membrane swelling caused a reduction in the separation factor. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 47–58, 1999     

Preferential separation of ethanol from aqueous solution through hydrophilic polymer membranes

The pervaporation behaviors of aqueous ethanol mixtures through the poly(ethylene oxide) (PEO)/chitosan (CS) blend membrane were investigated. The results show that both CS and PEO/CS membrane preferentially permeate ethanol at a lower alcohol concentration in feed, and the selectivity of CS membrane toward alcohol can be greatly improved by introducing hydrophilic polymer PEO into CS. The PEO/CS blend membrane gave a separation factor of 4.4 and a flux of 0.9 kg m⁻² h for 8 wt % of ethanol in the feed at 20°C. At the same time, the reason introducing PEO can improve alcohol-permselectivity of CS membrane is explained on the basis of experimental data. Blending with PEO made the structure of CS chain looser, which resulted in ethanol molecules passing through easily, on the other hand, strengthened the ability of forming water clusters that inhibit the permeation of water molecules. From the experimental results, although the PEO/CS blend membrane was not a usable membrane with high selectivity to alcohol, a new method to prepare alcohol-permselective membranes appears to be developed by modifying hydrophilic polymers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1145–1151, 1999     

渗透汽化原位分离耦合拜氏梭菌丁醇发酵的研究

以筛选得到的聚二甲基硅氧烷（polydimethylsiloxane,PDMS）-聚偏氟乙烯（polyvinylidene fluoride,PVDF）复合膜为分离用膜,开展了拜氏梭菌（Clostridium beijerinckii）ZL01丁醇发酵与渗透汽化原位分离耦合的研究,结果表明：分批发酵-渗透汽化原位分离耦合与分批发酵相比,初始葡萄糖质量浓度从50 g/L提高至90 g/L;在90 g/L的初始葡萄糖质量浓度下,发酵结束时发酵液和渗透液中的丁醇总产量从13.2 g/L提高到16.9 g/L,总溶剂（丙酮（acetone）、丁醇（butanol）、乙醇（ethanol）,简称ABE）产量从17.8 g/L提高到24.3 g/L,葡萄糖利用率从59.4%提高到95.7%。另外,分离过程中膜的总渗透通量平均为705 g/（m2·h）,丁醇分离因子平均为19.0;经渗透汽化分离,渗透液可直接进入下一步蒸馏阶段,其中丁醇和总溶剂ABE质量浓度分别为178 g/L和292 g/L,与分批发酵工艺中发酵液直接进入蒸馏塔相比,丁醇和总溶剂ABE质量浓度分别提高了10.9 倍和14.1 倍,可大大降低蒸馏能耗。     

蒸汽相转化涂晶法SAPO-34分子筛膜的制备及表征

采用一种新型涂晶方法即蒸汽相转化涂晶法, 在廉价大孔α-Al₂O₃载体上水热合成制备高质量的SAPO-34分子筛膜。该方法能够有效修复α-Al₂O₃载体的大孔缺陷, 通过制备平整均匀的晶种层, 最终得到了连续并且无明显“针孔”缺陷的SAPO-34膜。实验考察了浆料中添加尺寸分别为2 μm、1 μm、500 nm及100 nm的晶种对形成晶种层及分子筛膜的影响, 并将制备的分子筛膜用于渗透汽化异丙醇脱水实验。在75℃下对90wt%的异丙醇/水混合物具有优良的分离性能, 其通量和分离系数分别为1.396 kg/(m²·h)和973。     

"充填型"复合膜脱除水中微量有机氯化物的研究

利用等离子体照射引发接枝聚合方式制备了具有"充填型"结构的复合膜,在渗透汽化膜分离过程中研究了其从水中脱除微量有机氯化物的分离性能.该复合膜由两种材料组成;耐溶剂性能优良的高密度聚乙烯多孔基膜和接枝聚合后充填于基膜微孔中的聚丙烯酸甲酯,后者形成渗透汽化过程的分离选择性.使用FT-IR光谱图证实基膜接枝后表面存在羰基,表明形成接枝聚合的复合膜.在室温下进行渗透汽化实验,能够有效脱除水中微量的二氯甲烷、三氯甲烷和三氯乙烯,其中脱除二氯甲烷的渗透汽化分离因子超过2000,渗透通量达到120 g·(m2·h)- 1.