Separation of a C_(3)H_(6)/C_(2)H_(4) mixture using Pebax^(■) 2533/PEG600 blend membranes

In industry, ethylene(C_(2)H_(4))/propylene(C_(3)H_(6)) separations are usually performed by a cryogenic process,which is energy intensive. Membrane separation technology is an alternative separation process that saves energy and is efficient. In this study, blend membranes were prepared by doping polyethylene glycol(PEG600) into a poly(ether-block-amide)(Pebax^(■) 2533) matrix and were used to separate the C_(2)H_(4)/C_(3)H_(6) mixture. The PEG 600 and Pebax^(■) 2533 polymers have good compatibility because they share hydrogen bonds. The addition of PEG600 is conducive to the hydrophilicity and the free volume of blend membranes, and it is also conducive to the solubility of C_(2)H_(4) and C_(3)H_(6) in the membranes, which improves the ability of the membranes to separate this gas pair. The Pebax^(■) 2533/PEG600 blend membrane with 15%(mass) PEG600 showed the highest separation performance in our investigated membranes, with a C_(3)H_(6)/C_(2)H_(4) selectivity of 8.9 and a C_(3)H_(6) permeability of 196 barrer(1 barrer = 1.33×10^(14)m^(3)(STP)·m·m^(-2)·s^(-1)·kPa^(-1)) at 238 K and 0.2 MPa, which is higher than that of the Pebax^(■) 2533/NaY-6%(mass) membrane(α_(C_(3)H_(6)/C_(2)H_(4)) =6.5, P_(C_(3)H_(6))=211 barrer) reported in our previous work. It is confirmed that incorporating PEG600 into the Pebax^(■) 2533 matrix to fabricate blend membranes is an efficient strategy for separating light olefins.

Fabrication of Poly(vinylidene fluoride) /Polysulfone Flat Blend Membranes via Thermally Induced Phase Separation Process for Water Treatment

Poly(vinylidene fluoride) /polysulfone(PVDF/PSF) flat blend membrane was prepared via thermally induced phase separation(TIPS) technique.The membrane formation mechanism and membrane structure were investigated and the effects of PSF/PVDF weight ratio on morphology,crystallinity,porosity,and mechanical properties of the membrane were discussed.The relationship between membrane structure and performances,such as pure water flux and the rejection of carbonic black,was also discussed.It was found that solid-liquid(S-L) phase separation occurred for the PVDF/PSF/diluent system.The addition of PSF influences structure and crystallinity of the membrane,which in turn influences mechanical properties and performances of the membrane.The results reveal that it is possible to obtain network structure via S-L phase separation by blending the polymer,which has a partial compatibility with PVDF.

Polyvinyl acetate/poly(amide-12-b-ethylene oxide) blend membranes for carbon dioxide separation

In this paper,blend membranes from polyvinyl acetate(PVAc)and block copolymer poly(amide-12-b-ethylene oxide)(Pebax1074)are prepared by solution casting and solvent evaporation method.Although they are homogeneous on a macro-scale,the observations from DSC and SEM indicate micro-phase separation for PVAc/Pebax1074 blend membranes.With the increase of Pebax1074 content,gas permeabilities of CO2,H2,N2and CH4all increase greatly.PVAc/Pebax1074 blend membranes with high PVAc content are appropriate for CO2/CH4separation.The temperature dependence of gas permeability is divided into rubbery region and glassy region.The activation energies of permeation in rubbery region are smaller than those in glassy region,and they all decrease with increasing Pebax1074 content.For N2,H2and CH4,their gas permeation properties are mainly influenced by the dual-mode sorption and hydrostatic pressure effect.But for CO2,its permeability increases with the increase of pressure due to CO2-induced plasticization effect,which is more obvious for PVAc/Pebax1074 blend membranes with high PVAc content.

Poly(amide-6-b-ethylene oxide)/[Bmim][Tf2N] blend membranes for carbon dioxide separation

Poly（amide-6-b-ethylene oxide）（Pebax1657）/1-butyl-3-methylimidazo-lium bis[trifluoromethyl）sulfonyl]-imide（[Bmim][Tf2N]） blend membranes with different [Bmim][Tf2N] contents were prepared via solution casting and solvent evaporation method. The permeation properties of the blend membranes for CO2, N2,CH4 and H2 were studied, and the physical properties were characterized by differential scanning calorimeter（DSC） and X-ray diffraction（XRD）. Results showed that [Bmim][Tf2N] was dispersed as amorphous phase in the blend membranes, which caused the decrease of Tg（PE） and crystallinity（PA）. With the addition of [Bmim][Tf2N], the CO2 permeability increased and reached up to approximately 286 Barrer at 40 wt%[Bmim][Tf2N], which was nearly double that of pristine Pebax1657 membrane. The increase of CO2 permeability may be attributed to high intrinsic permeability of [Bmim][Tf2N], the increase of fractional free of volume（FFV） and plasticization effect. However, the CO2 permeability reduced firstly when the [Bmim][Tf2N]content was below 10 wt%, which may be due to that the small ions of [Bmim][Tf2N] in the gap of polymer chain inhibited the flexibility of polymer chain; the interaction between Pebax1657 and [Bmim][Tf2N]decreased the content of EO units available for CO2 transport and led to a more compact structure. For Pebax1657/[Bmim][Tf2N] blend membranes, the permeabilities of N2, H2 and CH4decreased with the increase of feed pressure due to the hydrostatic pressure effect, while CO2 permeability increased with the increase of feed pressure for that the CO2-induced plasticization effect was stronger than hydrostatic pressure effect.

Adsorptive removal of iron and manganese ions from aqueous solutions with microporous chitosan/polyethylene glycol blend membrane

Microporous chitosan （CS） membranes were directly prepared by extraction of poly（ethylene glycol） （PEG） from CS/PEG blend membrane and were examined for iron and manganese ions removal from aqueous solutions. The different variables affecting the adsorption capacity of the membranes such as contact time, pH of the sorption medium, and initial metal ion concentration in the feed solution were investigated on a batch adsorption basis. The affinity of CS/PEG blend membrane to adsorb Fe（II） ions is higher than that of Mn（II） ions, with adsorption equilibrium achieved after 60 min for Fe（II） and Mn（II） ions. By increasing CS]PEG ratio in the blend membrane the adsorption capacity of metal ions increased. Among all parameters, pH has the most significant effect on the adsorption capacity, particularly in the range of 2.9-5.9. The increase in CS/PEG ratio was found to enhance the adsorption capacity of the membranes. The effects of initial concentration of metal ions on the extent of metal ions removal were investigated in detail. The experimental data were better fitted to Freundlich equation than Langmuir. In addition, it was found that the iron and manganese ions adsorbed on the membranes can be effectively desorbed in 0.1 mol/L HCl solution （up to 98% desorption efficiency） and the blend membranes can be reused almost without loss of the adsorption capacity for iron and manganese ions.

SYNTHESIS OF AN AMPHIPHILIC PPESK-g-P(PEGMA)GRAFT COPOLYMER VIA ATRP AND ITS USE IN BLEND MODIFICATION OF PPESK MEMBRANES

Preparation of an amphiphilic graft copolymer having poly(phthalazinone ether sulfone ketone)(PPESK) as main chains was carried out by atom transfer radical polymerization(ATRP).The precursor,chloromethylated PPESK (CMPPESK),was prepared by using chioromethylether as chloromethylation agent.Then,poly(ethylene glycol) methyl ether methacrylate(PEGMA) was used as monomer to synthesize PPESK-g-P(PEGMA) by ATRP method under the catalysis of a cuprous chloride/2,2'-bipyridyl system.PPESK/PPESK-g-P(PEGMA) blend m...

PREPARATION OF HIGH DENSITY POLYETHYLENE/POLYETHYLENE-BLOCK-POLY(ETHYLENE GLYCOL)COPOLYMER BLEND POROUS MEMBRANES VIA THERMALLY INDUCED PHASE SEPARATION PROCESS AND THEIR PROPERTIES

High density polyethylene （HDPE）/polyethylene-block-poly（ethylene glycol） （PE-b-PEG） blend porous membranes were prepared via thermally induced phase separation （TIPS） process using diphenyl ether （DPE） as diluent. The phase diagrams of HDPE/PE-b-PEG/DPE systems were determined by optical microscopy and differential scanning calorimetry （DSC）. By varying the content of PE-b-PEG, the effects of PE-b-PEG copolymer on morphology and crystalline structure of membranes were studied by scanning electron microscopy （SEM） and wide angle X-ray diffraction （WAXD）. The chemical compositions of whole membranes and surface layers were characterized by elementary analysis, Fourier transform infrared spectroscopy-attenuated total reflection （FTIR-ATR） and X-ray photoelectron spectroscopy （XPS）. Water contact angle, static protein adsorption and water flux experiments were used to evaluate the hydrophilicity, antifouling and water permeation properties of the membranes. It was found that the addition of PE-b-PEG increased the pore size of the obtained blend membranes. In the investigated range of PE-b-PEG content, the PEG blocks could not aggregate into obviously separated domains in membrane matrix. More importantly, PE-b-PEG could not only be retained stably in the membrane matrix during membrane formation, but also enrich at the membrane surface layer. Such stability and surface enrichment of PE-b-PEG endowed the blend membranes with improved hydrophilicity, protein absorption resistance and water permeation properties, which would be substantially beneficial to HDPE membranes for water treatment application.

STUDY OF COMPOSITE MEMBRANE OF CELLULOSE ACETATE OR POLYVINYL ALCOHOL BLENDED WITH METHYLMETHACRYLATE-ACRYLIC ACID COPOLYMER FOR PERVAPORATION SEPARATION

In this paper, methylmethacrylate-acrylic acid MMA-AA hydrophilic and hydrophobic copolymers were prepared by copolymerization for preparing membrane materials. The composite membrane of cellulose acetate (CA) blended with MMA-AA hydrophobic copolymer was used for the separation of methanol from pentane-methanol mixture. When the methanol concentration was only 1 wt%, the permeate flux still maintained at 350 g/m(2)h and separation factor was as big as 800. The composite membrane of PVA (polyvinyl alcohol) blended with MMA-AA hydrophilic copolymer was used for the separation of ethanol-water mixture. The permeate flux was increased to 975 g/m(2)h at 74 degrees C and the separation factor reached 3000 at 25 degrees C. The PVA/MMA-AA blended membrane surface modified by ammonia plasma was also investigated for separating ethanol-water mixture. Both permeate flux and separation factor of the membrane was improved. However, there was no obvious difference of plasma treatment time in the interval of 20 similar to 40 min.

Research and Application Progress of Silk Fibroin Membranes

This paper mainly introduced the preparation of silk fibroin membranes and their structural change characteristics.Silk fibroin membranes can be used as tissue engineering materials,enzyme-immobilizing membranes,biosensors and drug controlled-release membranes and other different materials.They have excellent characteristics such as non-toxic,non-polluting and degradable,and thus have broad application prospects.

A Simple and Effective Method to Fabricate Separation Membranes for Dehydration of Natural Gas

PBT/PEG_(1000)composite membranes were prepared by the phase inversion method and were used to dehydrate natural gas.In this study,evaporation time,coagulation bath concentration,and additives in casting solution were investigated,respectively,on the selectivity and permeability of separation membranes,and optimal conditions were found to include an evaporation time of 30 sec,an 100%PEG400-containing coagulation bath and 2%of PVA used as the additive.The H_(2)O/CH_(4)selectivity reached over 3600,which is about 20 times more selective than the original membrane.It provides a simple and effective preparation method to fabricate membranes for dehydration of methane gas.

Improved blending strategy for membrane modification virtue of surface segregation using surface-tailored amphiphilic nanoparticles

Membrane modification is one of the most feasible and effective solutions to membrane fouling proble.m which tenaciousl.y hampers .the furher au .gmentation of me .rnbrane sep.aration technology.Blending modification with nanoparticles （NPs）, owing to the convenience of being incorporated in established membrane.p.rodu. ction lines, possesses an advantag, eous viability in practical applications.However, the existing blending strategy suffers from a low utilization efficiency due to NP encasement by membrane matrix. The current study proposed an improved blending modification approach with amphiphilic NPs （aNPs）, which were prepared through silanization using 3-（Trimethoxysilyl）propyl methacrylate （TMSPMA） as coupling agents and ZnO or SiO2 as pristine NPs （pNPs）, respectively.The Fourier transform infrared and X-ray photoelectron spectroscopy analyses revealed thepresence of appropriate organic components in both the ZnO and SiO2 aNPs, which verified the success of the silanization process. As compared with the pristine and conventional pNP-blended membranes, both the ZnO aNP-blended and SiO2 aNP-blended membranes with proper silanization （100% and 200% w/w） achieved a significantly increased blending efficiency with more NPs scattenng on the internal and external membrane surfaces under scanning electron microscope observation. This improvement contributed to the increase of membrane hydrophilicity. Nevertheless, an extra dosage of the TMSPMA led to an encasement of NPs, thereby adversely affecting the properties of the resultant membranes. On the basis of all the tests, 100% （w/w） was selected as the optimum TMSPMA dosage for blending modification for both the ZnO and SiO2 types.

Effect of Konjac Glucomannan on Sodium Alginate Membrane

This paper introduces a blended membrane which is prepared by coagulation of sodium alginate and konjac glucomannan（KGM） in an aqueous solution, and studies the effect of different concentrations of KGM on sodium alginate films. The structural characterization of prepared blend film was implemented by scanning electron microscopy（SEM） and Fourier transform infrared spectroscopy（FT-IR）, and the optimum ratio was determined by comparing fracture elongation, moisture absorption and moisture retention. The results indicate that the two polysaccharide molecules, sodium alginate and KGM, in the blend membrane have a good compatibility. The surface of blend film is smooth and uniform. The addition of KGM can significantly improve the moisture absorption and moisture retention performance of sodium alginate film, and its mechanical performance is also improved to some extent. The ratio of sodium alginate and KGM is 3.2∶1.5.

Mixed Matrix Membranes of Polysulfone/Polyimide Reinforced with Modified Zeolite Based Filler: Preparation, Properties and Application

In this work, polysulfone/polyimide（PSf/PI） mixed matrix membranes were fabricated by reinforcement of modified zeolite（MZ） particles through solution casting method for investigation of antibacterial activity against two gram negative bacteria（Salmonella typhi, Klebsella pneumonia） and two gram positive bacteria（Staphylococcus aureus, Bacillus subtilis）. The modified zeolite particles were incorporated to PSf and PI matrix and the influence of these particles on thermal, mechanical and structural properties was evaluated. The morphological evolution was investigated through scanning electron microscopy（SEM） and transmission electron microscopy（TEM） analysis, which revealed good compatibility between organic polymer matrix and inorganic filler. Mechanical stability was investigated by tensile testing while thermal analysis was evaluated by thermogravimetric analysis（TGA） and differential scanning calorimetry（DSC）. This revealed improvement in thermal properties with increasing filler concentration from 1 wt% to 10 wt%. Structural analysis was successfully done using X-ray diffraction analysis（XRD） and Fourier transform infrared（FTIR） spectroscopy. Solvent content of fabricated mixed matrix membranes was observed to decrease while moving from more hydrophilic to less hydrophilic solvent. However, addition of filler content enhanced the porosity of fabricated membranes. The synthesized mixed matrix membranes exhibited good antibacterial activity and the highest activity was shown by PSf/PI/MZ mixed matrix membrane. Therefore, the combination effect of PSf, PI and MZ sufficiently enhanced the antibacterial activity of mixed matrix membranes.