Degumming of crude soybean oil by ultrafiltration using polymeric membranes

In this study, the ability of two ultrafiltration polymeric membranes to perform the degumming of a crude soybean oil/hexane mixture is tested. The performance of both membranes is defined in terms of their permeation flux, permeate color, and rejection of phospholipids. One of the membranes was synthesized in our laboratories from polyvinylidenefluoride (PVDF); the other one is a commercially available membrane made of polyimide. The degumming experiments were done in a stirred dead-end ultrafiltration cell pressurized with N₂. Results show that tested membranes are suitable for removing phospholipids from the crude oil/hexane miscella in the range of temperature and transmembrane pressure utilized in this work. Both membranes have high selectivity regarding phospholipids and produce a moderate reduction in permeate color. The PVDF membrane gives permeate fluxes up to threefold larger than those obtained with polyimide membrane at the same operational conditions, making the former more suitable for use at industrial scale.     

Specialty polymeric membranes

Summary Pervaporation of acetic acid/water mixture was investigated through uncrosslinked and crosslinked polybutadiene membranes. Crosslinked polybutadiene membrane permeated acetic acid in preference to water indicating that polybutadiene must be a candidate for a permselective membrane material for acetic acid separation from its aqueous solution.     

Overcoming mass‐transfer limitations in partial hydrogenation of soybean oil using metal‐decorated polymeric membranes

The conventional soybean oil hydrogenation process (metal catalyst on solid support particles slurried in oil, H₂ bubbled through the oil) is compared with metal‐decorated integral‐asymmetric polyetherimide (PEI) membranes, as far as changes in temperature and pressure are concerned. Using metal‐decorated polymeric membranes, H₂ is supplied to the catalytic sites by permeation from the membrane substructure. As opposed to the slurry process, metal‐decorated membranes show only slightly increased trans fatty acid (TFA) formation when the temperature is raised (50–90°C) to accelerate the process. This is likely due to the efficient and to some extent self‐regulating H₂ supply directly to the catalytic sites on the membrane skin. The hydrogenation rate and TFA formation of the metal‐decorated membrane process show a minor dependence on pressure. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Permeation of molecules through different polymeric membranes

Permeation of molecules through the membranes plays an important role in immobilized cell systems. Permeation of molecules like glucose and bovine albumin serum was studied through chitosan, polyvinyl alcohol, and polyvinyl acetate membranes using a flow cell made of two detachable compartments. Permeation of molecules through chitosan, polyvinyl alcohol, and polyvinyl acetate membranes increases with decrease in hydrophobic characteristics of the membrane. Permeation of molecules also show its dependency on the molecular weight of the solute. Distribution coefficient of glucose and bovine serum albumin in these polymeric membranes measured by equilibration technique indicates that permeation of molecules through these membranes follows pore type mechanism. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3469–3472, 1999     

New polymeric materials for reverse osmosis membranes

The results obtained from investigations on new aromatic polyamides containing carboxylic groups suitable for reverse osmosis are reported. The polymers are fabricated into asymmetric membranes by the Loeb-Sourirajan technique. The effects of fabrication conditions were also investigated to yield the optimum membranes for brackish water and sea water desalination, respectively. Performance characteristics of the membranes are 0.30 m³/m²·day above 98% rejection at 70 kg/cm²-35000 ppm NaCl, and 1.0–1.15 m³/m²· day, 97–98% rejection at 40 kg/cm²-5000 ppm NaCl. They exhibited good resistance in the tests carried out in alkaline medium (pH 10) and acid medium (pH 4).     

填充型有机-无机杂化分离膜研究进展

根据有机、无机组分间相互作用类型对有机-无机杂化膜进行了分类,重点论述了无机粒子填充型有机-无机杂化膜的最新研究进展,归纳了此类杂化膜的优异性能,总结了无机粒子的物理化学性能、含量、尺寸及其与聚合物的相容性等因素对此类杂化膜结构和性能的主要影响。最后提出了目前研究中存在的一些问题,并对其发展做出了简要的述评。     

Highly selective polymeric membranes for gas separation

Polymeric membranes have gained an important place in chemical technology and are used in a broad range of applications. The key property that is exploited is the ability of a membrane to control the permeation rate of a chemical species through the membrane. The goal is to allow one component of a mixture to permeate the membrane freely, while hindering permeation of other component. To accomplish this, we proposed a novel concept of a (universal) ‘organic molecular sieve’ and experimentally proved its possibility by showing that organic polymer molecules at the interface between the permeable phase and the impermeable phase play the role of molecular sieves. This resulted in a significantly improved selectivity in gas separation, in fact going over the so-called ‘upper-bound’ sought for the past 30 years by many researchers but without much success. Since, this is not size selective like an inorganic molecular sieve but diffusion selective (the compatibilizer works like a molecular sieve to separate one gas molecules from the other), it can be used for the preparation of polymeric membranes for separation of any gas molecules pair. Because of polymer processability, this method is quite promising for the continuous mass production of polymeric membranes for real applications, especially when the polymers are insoluble to common solvents so that solution based techniques are hard to apply. This strategy can be applicable to various separation processes of many chemicals and gases.     

Purification of Aspergillus carbonarius polygalacturonase using polymeric membranes

BACKGROUND: Microfiltration (MF: 70–450 nm) and ultrafiltration (UF: 10–500 kDa) membranes were used to eliminate carbohydrates and other non‐protein impurities from Aspergillus carbonarius culture broth containing polygalacturonase enzyme (EC 3.2.1.15) that would otherwise interfere with the purification processes and lead to enzyme loss. Further, diafiltration was attempted to improve the elimination of impurities as well as recovery of enzymes. RESULTS: MF resulted in removal of 2–25% carbohydrates with an enzyme recovery of 69–82% from the crude culture broth owing to the secondary layer formation. UF with 10 kDa membrane eliminated most of the carbohydrates (96%), phosphate salts and total acids with a recovery of 96% polygalacturonase and resulted in greater productivity. Using the above procedure, the enzyme was concentrated nearly 10‐fold while the purity improved from 4.6 to 49.4 U mg^?1 of dry matter. CONCLUSIONS: The results of this study focused on the elimination of carbohydrates and other non‐protein impurities showed that UF could be used efficiently as a primary purification step during downstream processing of microbial culture broths containing enzymes. The present approach will ensure complete elimination of non‐protein impurities thereby reducing the losses and difficulties in the subsequent purification steps. Copyright © 2008 Society of Chemical Industry     

Effect of ultrasound irradiation on polymeric microfiltration membranes

The effect of powerful ultrasound (US) at a frequency of 40 kHz and an intensity of 1.43-3.57 W·cm⁻² on polymeric microfiltration membranes was evaluated. Four different polymers including polyethersulfone, nylon 6(N₆), the mixed ester of cellulose nitrate with cellulose acetate (CN-CA) and polyvinylidenefluoride (PVDF), with an average pore diameter of 0.45 μm, were investigated. The evolution of the polymeric structure exposed to US was followed by the measurements of the water flux and the rejection rate of 1 wt% isolated soybean protein. The result shows that important variations occur on some membranes after irradiation. In addition, microscopic photos of irradiated membranes by field emission scanning electron microscopy were taken in order to directly observe the change on membrane surface. It has been shown that, over the four materials tested, only the PVDF presents no significant change in the measured parameters with increase of the duration at the low intensity of ultrasound irradiation, whereas the others are affected by ultrasound treatment.     

Swelling behavior of polymeric membranes to metalworking fluids

In some working places, such as metal manufacturing or automotive services, mechanical hazards commonly occur along with chemical hazards, particularly metalworking fluids (MWFs). The presence of these chemicals could modify the properties of gloves made from polymeric materials and thus reduce their protective properties against chemical contamination (solvent, MWFs) and mechanical risks (puncture and cutting). This work focused on determining the swelling characteristics and the resistance of six polymeric membranes which were exposed to seven industrial MWFs. We found that the swelling tests can be used to classify the potential of coating polymers in descending order of their resistance to MWFs: nitrile, polyurethane > poly(vinyl chloride), neoprene > butyl, latex. The analysis by multiple linear regression showed, for the first time, that the density or the viscosity‐gravity constant of the fluid and Hansen's solubility parameters of the polymers have a significant impact on the swelling of polymer. For the first time, two new multiple regression models have been proposed, to predict the swelling phenomena of polymers under various MWFs with an accuracy of ≈80%. The effect of temperature on mechanical properties and morphology of material was also examined. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45717.     

Deacidification of model vegetable oils using polymeric membranes

Selectivity of polymeric hydrophobic nonporous and hydrophilic nanofiltration (NF) membranes was assessed for the deacidification of model vegetable oils with and without addition of organic solvents. In the model undiluted system, oleic acid permeated preferentially over triacylglycerols in the nonporous membrane, over a wide range of concentrations (?5–70%). The effect of oleic acid concentration on selectivity indicated that the solubility of triacylglycerols in oleic acid played a role in determining the selectivity, besides the solubility and diffusivity of the permeating components. Dilution with hexane improved oil flux by 14‐fold; however, membrane selectivity was completely lost as both triacylglycerols and oleic acid permeated along with the solvent, which clearly showed that the solvent played a greater role than the membrane. Processing of the model oil after diluting with acetone showed that oleic acid was retained less than triacylglycerols by the NF membrane, resulting in higher selectivity (7), indicating its potential. However, the selectivity decreased during successive runs, owing to the gradual loss of hydrophilicity due to polarity conditioning of the membrane. The differences in molecular size, solubility, diffusivity and polarity between triacylglycerols and oleic acid appear insufficient for achieving direct deacidification in terms of reasonable selectivity and throughput with these two membranes. Direct deacidification using membranes still remains as a challenge.     

The art of surface modification of synthetic polymeric membranes

The development in the area of surface modification of polymeric synthetic membranes since 2000 is reviewed. Many patents, articles, and reviews have been written on the development in the area of surface modification of polymeric synthetic membranes subjected to RO, UF, NF, gas separation (GS), and biomedical applications, mainly since 2000, but recently more attention has been given to the modification of their surfaces to obtain desirable results. In particular, most emphasis has been given to plasma treatment, grafting of polymers on the surface, and modifying the surfaces by adding SMMs (surface‐modifying molecules). New additives are synthesized to make the polymeric membrane surfaces either to be more hydrophilic or hydrophobic, aimed at improvement in selectivity and permeability of the membranes for GS, NF, and RO. Improvement in antifouling by surface modification is also a popular topic in the membrane industries. In the last 8 years, tremendous research efforts have been made on the development of antifouling membranes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

高分子致密膜内渗透现象的同一性研究

在渗透汽化（PV）和蒸汽渗透（VP）膜分离过程,利用高分子膜材料对原料中不同组分的溶解度与扩散系数不同实现混合物分离.由于两种过程原料状态分别呈现液态和蒸汽形式,长期以来作为两种膜分离过程展开研究,其传质推动力都是组分在膜中的化学位梯度.为了从热力学和传质角度研究PV和VP膜分离过程,本文设计了特殊的渗透池,可以在同一渗透池中同时进行渗透汽化和蒸汽渗透膜分离过程,保持气液界面为热力学平衡状态.使用PVA/PAN复合膜进行水/乙醇混合物以及水/异丙醇混合物的PV和VP渗透实验,对两个过程中渗透通量随浓度变化情况进行了分析和比较.实验结果和理论分析表明：溶液的PV过程和与之呈相平衡的蒸汽相的VP过程在一定温度范围内,当原料中水含量较低的情况下具有相同的渗透通量,其传质遵从溶解扩散机理;当原料溶液中水含量较高时,PV过程中膜溶胀现象较为严重,渗透通量存在一定差别.     

Optimization of the elastic modulus for polymeric nanocomposite membranes

The mechanical properties of polymeric membranes are critical factors for a successful and durable application in water treatment technologies. Fabricating membranes with optimal mechanical properties require delicate balancing between material, additives, processing conditions, porosity, and many other variables. Several variables to be optimized demands detailed experimental and computational investigations. The design of experiments (DOEs) technique using a validated framework with a computational model for the prediction of the elastic behavior can lower the number of conducted experiments for optimal membrane fabrication conditions. In this study, optimization of the elastic modulus of polymeric membranes is performed using DOE with computational modeling and validated with experiments. The optimum storage modulus of polymeric nano-filled membranes is determined at an operating temperature of 35°C. DOE is employed with a three-factor–three-level problem. The Taguchi DOE is utilized to obtain the experiments scheme, followed by the prediction of the storage modulus and fabrication of the polymeric nano-filled membrane with the optimum modulus. Predicted results demonstrate that the modulus of polyether sulfone (PES) reinforced with 0.3 wt.% halloysite nanotubes (HNTs) is the optimum combination. The fabricated PES/0.3 wt.% HNT membrane is in good agreement with the predicted modulus with a percentage error of 3%.     

Separation of gaseous mixtures with asymmetric dense polymeric membranes

The advantages of using asymmetric polymeric membranes with a dense skin and a microporous backing for separation of permanent gas mixtures have been p     

Transport of small molecules through mechanically elongated polymeric membranes

This contribution presents an analysis of the problem of diffusion through membranes, incorporating a realistic downstream boundary condition. The analysis can be applied to operations involving geomembranes. Graphs are presented to show the effect of the various dimensionless parameters. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1200–1203, 2005     

Electrochemical and electrokinetic characterization of cellulose acetate polymeric membranes

The electrochemical and electrokinetic aspects of cellulose acetate membranes of varying pore structure and desalting abilities have been investigated. The electrochemical studies included measurement of conductance and membrane potential for various membrane electrolyte systems. The electrokinetic characterization was made from streaming potential measurements. The data obtained are explained in terms of interfacial double layer phenomena prevalent in porous permselective barrier systems. The average pore diameter evaluated independently is also presented and an attempt has been made to understand the solute–water transport in terms of weak ionic character of membrane surface.     

Recent advances in polymeric membranes for CO2 capture

Membrane and membrane process have been considered as one of the most promising technologies for mitigating CO₂ emissions from the use of fossil fuels. In this paper, recent advances in polymeric membranes for CO₂ capture are reviewed in terms of material design and membrane formation. The selected polymeric materials are grouped based on their gas transport mechanisms, i.e., solution‐diffusion and facilitated transport. The discussion of solution‐diffusion membranes encompasses the recent efforts to shift the upper bound barrier, including the enhanced CO₂ solubility in several rubbery polymers and novel methods to construct shape-persisting macromolecules with unprecedented sieving ability. The carrier-bearing facilitated transport membranes are categorized based on the specific CO₂-carrier chemistry. Finally, opportunities and challenges in practical applications are also discussed, including post-combustion carbon capture (CO₂/N₂), hydrogen purification (CO₂/H₂), and natural gas sweetening (CO₂/CH₄).     

Processing vegetable oils using nonporous denser polymeric composite membranes

Membrane processing offers several advantages over conventional processes for edible oil refining. In recent years, processing solvent-extracted, screw-pressed, and used frying oils using nonporous denser polymeric composite membranes without pretreatment and addition of chemicals has been extensively investigated. In the present review, results obtained with real and model systems have been summarized and a comprehensive explanation is provided on the mechanism of rejection and differential permeation of oil constituents. Phospholipid-TG and pigment-TG systems are construed as conventional solute-solvent systems, and tocopherol-TG and FFA-TG systems are treated as liquid mixtures exhibiting differential permeability. Dense membrane theory appears more applicable than the reverse osmosis theory in qualitatively explaining the differential permeability of liquid constituents of the oil. Membrane processing of oils appears to have the potential to be a one-step process, especially for screw-pressed oils, in producing a premium-quality product. However, the development of suitable membranes that enable higher fluxes is necessary for industrial adoption of this technology.