Modified zeolitic–midazolate framework 8/poly(ether‐block‐amide) mixed‐matrix membrane for propylene and propane separation

In this study, we fabricated a dual‐layer PES–poly(ether‐block‐amide) (PEBA) composite membrane that included zeolitic–midazolate framework 8 (ZIF‐8) particles and evaluated it for propylene and propane separation under pure and mixed feed conditions. To improve the performance, compatibility, and distribution of particles in the polymer matrix, the ZIF‐8 particles were modified by 3‐(triethoxysilyl) propyl amine (APTES) and 3‐(trimethoxysilyl) propyl amine (APTMS) amino silane coupling agents. Particle modification did not have much effect on the structure and particle size and slightly reduced the membrane specific surface area. The modified particles tended to be in the soft section. At the high loading rate of modified particles, their appropriate compatibility increased the membrane gas permeability () and selectivity. APTES with the proper chain length compared with APTMS had a higher and the same selectivity. The best performance (by 32.1 gpu) was found in PES–PEBA–ZIF‐8–APTES 20%. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46273.     

Microwave synthesis of tubular zeolitic imidazolate framework ZIF-8 membranes for CO2/CH4 separation

The separation of CO₂/CH₄ is reported in detail by using zeolitic imidazolate framework (ZIF-8) membrane which was prepared on 3-aminopropyltriethoxysilane modified Al₂O₃ tube through microwave heating synthesis. Attributed to the preferential adsorption affinity of CO₂ over CH₄ and a narrow pore window of 0.34 nm, the ZIF-8 membrane shows high separation performances for the separation of CO₂/CH₄ mixtures. For the separation of equimolar CO₂/CH₄ mixture at 100°C and 2 bar feed (1 bar permeate) pressure, a CO₂ permeance of 1.02 × 10^?8 mol/m²· s· Pa and a CO₂/CH₄ selectivity of 6.8 are obtained, which is promising for CO₂ separation.     

Facile ZIF‐8 functionalized hierarchical micronanofiber membrane for high‐efficiency separation of water‐in‐oil emulsions

The efficient separation and recovery of oil from water‐in‐oil emulsion poses a great challenge because of the rapid development of the petrochemical industry throughout the world. In this study, a facile method to develop a ZIF‐8 functionalized hierarchical micronanofiber membrane for high‐efficiency oil/water separation was investigated. The electrospun PVDF/ZnO membrane was made, on which ZIF‐8 crystal seeds were then created with the revitalizing step and expanded in the growth step, and finally functionalized hierarchical micronanofiber PVDF‐g‐ZIF‐8 membrane was obtained. Results showed that oleophilic ZIF‐8 crystals on the surface of PVDF membrane dramatically increased the wettability of oil and tuned PVDF membrane from olephobicity to oleophilicity. The hydrophobic/lipophilic PVDF‐g‐ZIF‐8 membrane with a water contact angle up to 158° and a toluene contact angle down to 0° provides its separation efficiency for water‐in‐oil emulsion of 92.93% in an environmentally friendly and energy‐saving manner. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46462.     

Superelastic and hydrophobic-oleophilic modified melamine foam by ultralow amount of graphene for oil/water separation

Oil spills and organic chemical leakage have caused serious environmental problems, calling for highly effective adsorbents at low cost. Superelastic and hydrophobic-oleophilic modified melamine foams with ultralow amounts of well-dispersed graphene were prepared via dip-coating. The composite foams showed high selectivity for adsorbing various organic chemicals from water and could be regenerated easily. Moreover, excellent adsorption capacity ranging from 80 to 170 times its own weight was found depending on the density of organic chemicals. These coated foams show great potential for continuous oil/water separation and oil fume removal.     

Performance and mechanism of a hydrophobic–oleophilic kapok filter for oil/water separation

A natural vegetable fiber, kapok, was evaluated for its feasibility as filter material for separating immiscible liquids such as oil/water mixtures. Two types of oils, namely diesel and hydraulic, were investigated. Various simulated oily waters were prepared by mixing tap water with one of these oils to produce binary oil/water mixtures of varying oil percentages, such as 5%, 10% and 15% by weight. The effect of filter packing density on the dynamics of oil/water separation during the filtration process and the filtrate quality were investigated. Due to the hydrophobic–oleophilic surface characteristic of the kapok fiber, water could be filtered through the filter while oils were retained, causing separation of oil from water. The filtration efficiency for removal of diesel and hydraulic oil from their respective oily waters reached 100% and more than 99.4%, respectively, which showed an excellent performance of kapok in removing oils from oily waters. The hydraulic conductivity of the kapok filter was found to decrease with the advance of the oil front. The filtration rate of both types of oily waters decreased with increasing filter packing densities and influent oil contents. The kapok filter performed equally well in terms of total filtrate collected before breakthrough for the two different oils, albeit the filtrate rate could be viscosity dependent. A packing density of 0.07 g/cm³ was the optimum one for diesel and hydraulic oil removal. At breakthrough, the oil/water/air three-phase partition within the filter bed is a function of influent oil concentration, oil type, and packing density of the filter.     

碳纳米管-石墨烯气凝胶制备及其对水中乳化油的吸附特性

以改进的Hummers-Offeman法制备出的氧化石墨（GO）与羧基化多壁碳纳米管（CNTs-COOH）为原料,聚乙烯吡咯烷酮（PVP）为交联剂,乙二胺（EDA）为还原剂,水热还原法制得羧基碳纳米管-石墨烯复合气凝胶（CGA）。调整GO与CNTs-COOH的质量比获得密度在8.40～14.42 mg·cm^-3之间的气凝胶,并确定在GO：CNTs-COOH=3：1（质量）时得到的气凝胶的机械强度最优。通过扫描电子显微镜（SEM）、X射线衍射（XRD）、X射线光电子能谱（XPS）对所制备的CGA进行表征,得知GO与CNTs-COOH已成功还原组装成多孔状三维气凝胶结构。以水中乳化柴油作为研究对象,考察CGA样品在不同温度下对乳化柴油的吸附特性。结果表明,CGA的吸附量在前6 min迅速上升,在30 min左右达到吸附平衡,且平衡吸附量随温度升高而增加。吸附过程遵循准二级动力学模型,体系表观活化能为7.10 kJ·mol^-1。利用颗粒内扩散模型分析得出,CGA对乳化油的吸附分为外表面吸附过程和内部孔道吸附过程（内部大孔道吸附、中孔道和微孔道内扩散3个阶段）。     

Liquid–liquid phase separation in polysulfone/polyethersulfone/N‐methyl‐2‐ pyrrolidone/water quaternary system

To construct a phase diagram of the polysulfone (PSF)/polyethersulfone (PES)/N‐methyl‐2‐pyrrolidone (NMP)/water quaternary system, cloud point measurements were carried out by a titration method. The miscible region in the PSF/PES/NMP/water quaternary system was narrow compared to the PSF/NMP/water and PES/NMP/water ternary systems. The binary interaction parameters between PSF and PES were estimated by water sorption experiments. The calculated phase diagram based on the Flory–Huggins theory fit the experimental cloud points well. In addition to the usual polymer–liquid phase separation, polymer–polymer phase separation, which resulted in a PSF‐rich phase and a PES‐rich phase, was observed with the addition of a small amount of nonsolvent. The boundary separating these two modes of phase separation could be well described and predicted from the calculated phase diagrams with the estimated binary interaction parameters of the components. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2113–2123, 1999     

多嵌段聚醚改性聚(乙烯-乙烯醇)膜用于油水分离的研究

通过异佛尔酮二异氰酸酯(IPDI)与聚环氧乙烷-聚环氧丙烷-聚环氧乙烷(F127)三嵌段聚醚进行扩链反应,制备出具有手牵手结构的多嵌段聚醚(K-F127)。将F127与K-F127共混加入EVAL膜中,制备EVAL共混膜,并将其应用于油水分离中,比较了添加F127与K-F127对膜油水分离性能的影响。结果表明,扩链后K-F127的分子量增加为F127的2倍,共混添加F127与K-F127,均能显著提高EVAL膜的机械强度、亲水性和抗污染性能,但对膜结构无明显影响。由于分子量的增加,扩链后的K-F127对EVAL膜亲水性和通量的提高效果明显优于F127。     

New clay‐supported Ziegler–Natta catalyst for preparation of PE/Clay nanocomposites via in situ polymerization

Polyethylene/clay (PE/Clay) nanocomposites were prepared by the in situ polymerization of ethylene using the new Clay/butyl octyl magnesium (BOM)/Chloroform/EtOH/TiCl₄/tri ethyl aluminum (TEA) catalyst system in heptane where BOM and TEA were the support for the clay modification and cocatalyst, respectively. The influence of the modified clay using BOM on the catalyst and polymerization was investigated. Also, the effect of temperature, pressure, hydrogen, and the molar ratios of TEA/Ti on the catalyst yield and ethylene consumption (polymerization rate) were studied. It was found that the above clay‐supported catalyst was an efficient Ziegler–Natta type catalyst due to its suitable yield for the polymerization of ethylene toward the production of the PE/Clay nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Water–alcohol separation by pervaporation through zeolite‐modified poly(amidesulfonamide)

Pervaporation membranes were fabricated by blending different amount of zeolite NaA or NaX with three types of poly(amidesulfonamide) (PASA). The zeolite‐filled membranes were characterized by IR spectroscopy, SEM, sorption measurements, and wide‐angle X‐ray diffraction. By adding the proper amount of NaA into the polymer casting solutions, the resultant zeolite‐filled membranes exhibited improvement in both selectivity and permeability in the separation of 10% aqueous solutions of ethanol and propan‐1‐ol, as compared with the zeolite free membrane. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1323–1329, 2001     

Optimization of the property profile of poly‐L‐lactide by synthesis of PLLA‐polystyrene–block copolymers

Diblock and triblock copolymers of poly‐L ‐lactide (PLLA) and polystyrene (PS) were synthesized and the mechanical properties of these copolymers studied. Free radical polymerization of styrene in the presence of 2‐mercaptoethanol as functional chain transfer agent produced mono‐functionalized PS‐blocks which were used as macroinitiators in the subsequent ring opening polymerization (ROP) of L ‐lactide to produce the diblock copolymers. Furthermore a α‐ω‐bishydroxyl functionalized PS‐block was synthesized by RAFT, which was then engaged as bifunctional initiator for the ROP of L ‐lactide to provide the triblock copolymers PLLA‐PS‐PLLA. Through the copolymerisation and high molar masses, it was possible to achieve an improved mechanical property profile, compared with pure PLLA, or the analogous blends of PLLA and PS. A weight fraction of PS of 10–30% was found to be the optimal range for improving the heat deflection temperature (HDT), as well as mechanical properties such as ultimate tensile strength or elongation at break. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Sorption,swelling, and free volume of polybenzimidazole (PBI) and PBI/zeolitic imidazolate framework (ZIF-8) nano-composite membranes for pervaporation

We have studied alcohol- and water-induced swelling and sorption of PBI and PBI/ZIF-8 nano-composite membranes and characterized both dry and wet membranes by positron annihilation lifetime spectroscopy (PALS). The degrees of membrane swelling after immersing in alcohols and water follow the order of ethanol > methanol > water > n-butanol. Addition of ZIF-8 particles into PBI membranes suppresses the ethanol-, methanol- and water-induced PBI swelling. The water-induced swelling is subdued most severely because of the hydrophobic nature and rigid structure of ZIF-8 particles, while the n-butanol-induced swelling is enhanced owing to a greater free volume in the PBI/ZIF-8 membrane. The PALS studies confirm that the high pervaporation permeability of PBI/ZIF-8 membranes is attributed to the high fractional free volume (FFV) created by large cavities of ZIF-8 particles. In addition, the alcohol saturated PBI/ZIF-8 membranes have significantly smaller free volume radii than alcohol saturated PBI membranes. A correlation among FFV, pervaporation permeability and sorption diffusion coefficient has been developed. This study also demonstrates the importance of using PALS to characterize membrane structure changes in solvent-saturated membranes at a molecular level and to correlate pervaporation performance with solvent-induced swelling.     

Lewis acid–base property of P(VDF‐co‐HFP) measured by inverse gas chromatography

Poly (vinylidene fluoride‐co‐hexafluoropropylene) P(VDF‐co‐HFP) is an excellent material for polymer electrolytes of lithium ion battery. To enhance the lithium ion transference number, some metal oxides were often embedded into P(VDF‐co‐HFP). The promising mechanism for the increase in lithium ionic conductivity was Lewis acid‐base theory. In this experiment, the Lewis acid–base properties of P(VDF‐co‐HFP) were measured by inverse gas chromatography (IGC). The Lewis acid constant K_a of P(VDF‐co‐HFP) is 0.254, and the base constant K_b is 1.199. Compared with other polymers characterized by IGC, P(VDF‐co‐HFP) is the strongest Lewis basic polymers. Except aluminum ion, lithium ion is the strongest Lewis acidic ion according to their η value of Lewis acids. Therefore, a strong Lewis acid–base interaction will exist between lithium ion and P(VDF‐co‐HFP). This will restrict the transference of lithium ion in P(VDF‐co‐HFP). To enhance the lithium ion transference by blending other metal ions into P(VDF‐co‐HFP), it is suggested that the preferential ions should be Al³⁺, Mg²⁺, Na⁺, and Ca²⁺ because these metal ions have relative large η values. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Electrospinning of flux‐enhanced chitosan–poly(lactic acid) nanofiber mats as a versatile platform for oil–water separation

Environmentally friendly chitosan (CS)–poly(lactic acid) (PLA) nanofiber mats were designed and constructed by an electrospinning strategy. Studies on the wettability of the CS–PLA nanofiber mats showed that they possessed excellent hydrophobic and oleophilic properties in the pH range 1–12. A layered oil–water mixture was separated by CS–PLA nanofiber mats, and the oil flux of the mats collected by #10 stainless steel wire mesh (sample P‐10) was up to 511.36 L m^?2 h^?1, which was approximately 25 times higher than that of the mats collected by #0 stainless steel wire meshes (sample P‐N). The superior properties of the CS–PLA nanofiber mats may have been due to their tunable porous structure and fine flexibility. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45830.     

Toward efficient water/oil separation material: Effect of copolymer composition on pH‐responsive wettability and separation performance

Interest in functional soft matter with stimuli‐responsive wettability has increasingly intensified in recent years. From the chemical product engineering viewpoint, this study aims to fabricate reversible pH‐responsive polymeric surfaces with controllable wettability using [poly(2,2,3,4,4,4‐hexafluorobutyl methacrylate)‐block‐ poly(acrylic acid) (PHFBMA‐b‐PAA)] block copolymers. To attain this aim, three block copolymers with different PAA segment lengths were synthesized for the first time through Cu(0)‐mediated reversible‐deactivation radical polymerization and hydrolysis reaction. pH‐induced controllable wettability was achieved by spin‐coating the resulting block copolymers onto silicon wafers. Results showed that the pH‐responsive wetting behavior was introduced by incorporating the PAA block, and that the responsiveness of as‐fabricated surfaces was greatly influenced by PAA content. All three evolutions of water contact angle with pH shared a similar inflection point at pH 5.25. Furthermore, on the basis of the wetting properties and mechanism understanding, the application of copolymer coated meshes in layered water/oil separation was exploited. Given their superhydrophilicity and underwater superoleophobicity, PHFBMA₇₀‐b‐PAA₁₄₈ and PHFBMA₇₀‐b‐PAA₂₁₁ coated stainless steel meshes (SSMs) can efficiently separate water from different mixtures of organic solvent and water with high flux. However, considering long‐term use, the PHFBMA₇₀‐b‐PAA₁₄₈ coated SSM with good stability may be the best copolymer for water/oil separation. Therefore, a coordination of structure, composition, and functionality was necessary to enable practical applications of the functional materials. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1758–1771, 2016     

Synthesis of a carbon nanofiber/carbon foam composite from coal liquefaction residue for the separation of oil and water

A carbon nanofiber (CNF)/carbon foam composite was fabricated from coal liquefaction residue (CLR) through a procedure involving template synthesis of carbon foam and catalytic chemical vapor deposition (CCVD) treatment. The high solubility and high pyrolysis yield make CLR a promising carbon precursor for the synthesis of carbon materials using the template method. The carbon foam has cell size of about 500 μm and a porosity as high as 95 vol.%. Fe species naturally present in the CLR disperse homogeneously on the surface of the carbon foam acting as a catalyst in the CCVD process. After the CCVD treatment, the whole surface of the carbon foam is covered by entangled CNFs with external diameters of 20–100 nm and lengths of several tens of micrometers. The obtained CNF/carbon foam composites are effective selective adsorbents in the separation of oil and water, through a combination of hydrophobicity and capillary action.     

Pervaporation separation of water/dimethylformamide mixtures using poly(vinyl alcohol)‐g‐polyacrylamide copolymeric membranes

Grafted copolymeric membranes of poly(vinyl alcohol) with acrylamide (PVA‐g‐AAm) were developed and used in the pervaporation separation of water–dimethylformamide mixtures by varying the amount of water in the feed from 0 to 100%. From these data, the permeation flux, pervaporation separation index, diffusion coefficient, swelling index, and separation selectivity were calculated at 25, 35, and 45°C. The Arrhenius activation parameters for permeation flux ranged between 22 and 63 kJ/mol, while the activation energy for diffusion ranged between 23 and 67 kJ/mol. Separation selectivity was between 15 and 22. The highest permeation flux of 0.459 kg m^?2 h^?1 was obtained for the 93% grafted membrane at 90% of water in the feed mixture. The results are discussed using the principles of the solution–diffusion model. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 273–282, 2002