Benzene Permselectivity Research Articles

Selective removal of dilute benzene from water by poly(methyl methacrylate)-graft-poly(dimethylsiloxane) membranes containing hydrophobic ionic liquid by pervaporation

This paper focuses on the addition of hydrophobic ionic liquid, 1-allyl-3-butylimidazilium bis (trifluoromethane sulfonyl) imide ([ABIM]TFSI) to poly(methyl methacrylate)-graft-poly(dimethylsiloxane) (PMMA-g-PDMS) membranes, on the pervaporation characteristics for the removal of dilute benzene from an aqueous solution. When an aqueous solution of 0.05wt% benzene was permeated through [ABIM]TFSI/PMMA-g-PDMS membranes, they showed high benzene permselectivity and permeability. Both the benzene/water selectivity and permeability of the membranes were enhanced with an increase of [ABIM]TFSI, because the affinities of [ABIM]TFSI/PMMA-g-PDMS membranes for benzene were increased by introducing [ABIM]TFSI into the membranes. The [ABIM]TFSI localized in the PMMA layer of the microphase separated PMMA-g-PDMS membrane plays an important role as an absorbent to selectively partition benzene from the aqueous benzene solution.

Pervaporation of benzene/cyclohexane mixtures through poly(vinyl alcohol) membranes with and without β-cyclodextrin

β-cyclodextrin (β-CD)-filled cross-linked poly(vinyl alcohol) (PVA) membranes (β-CD/PVA/GA) were prepared using glutaraldehyde as the cross-linker, and these membranes showed strong benzene permselectivity. The permeation flux of β-CD/PVA/GA membranes increased when the β-CD content was 0–8 wt%, but permeation flux decreased slightly when the β-CD content was 8–20 wt%. The separation factor towards benzene increased when β-CD content was in the range 0–10 wt% and decreased slightly when the β-CD content was 10–20 wt%. Compared with the β-CDfree PVA/GA membrane, the separation factor of the β-CD/PVA/GA membrane for benzene to cyclohexane considerably increased from 16.7 to 27.0, and the permeation flux of benzene increased from 23.1 to 30.9 g/(m 2 h) for benzene/cyclohexane (50/50, wt) mixtures at 323 K. The analysis based on the solution–diffusion model and β-cyclodextrin inclusion phenomena (complex stabilities) revealed that β-CD in PVA membranes played an important role as a carrier to partition benzene selectively from benzene/cyclohexane mixtures.

Poly(vinyl alcohol)/chitosan blend membranes for pervaporation of benzene/cyclohexane mixtures

AbstractPoly(vinyl alcohol)/chitosan (PVA/CS) blend membranes were prepared by mixing the two polymeric homogeneous solutions. The interaction between PVA and chitosan arising from hydrogen bond was analyzed through intrinsic viscosity determination and Fourier transform infrared (FTIR) spectra, and there existed an incompatibility region in the blend membranes when chitosan content was 50 wt %. X‐ray diffraction (XRD) showed that the crystalline structure of PVA and chitosan was disrupted through blending. The incompatibility of two polymers and disrupted crystalline structure led to a less compact structure. The blend membranes were used to pervaporative separation of benzene/cyclohexane (Bz/Chx) mixtures. The effects of chitosan content in blend membranes, weight fraction of benzene in feed, and operating temperature on separation performance of Bz/Chx mixtures were investigated. Compared with pure PVA and pure chitosan membranes, blend membranes showed much higher permeation flux and slightly higher benzene permselectivity. As the weight fraction of benzene in feed increased, separation factor decreased but total permeation flux increased. And it was observed that total permeation flux increased and separation factor decreased with increasing operating temperature. The total permeation flux of blend membrane with 50 wt % chitosan was 51.41 g/(m2 h) and separation factor was 49.9 for Bz/Chx mixtures with 50 wt % of benzene at 323 K. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 167–173, 2006

Cross-linked smart poly(dimethylsiloxane) membranes for removal of volatile organic compounds in water

This paper focuses on the effects of fluorine cross-linker of the cross-linked poly(dimethylsiloxane) membranes from polydimethylsiloxane dimethylmethacrylate macromonomer (PDMSDMMA) and divinyl perfluoro- n-hexane (DVF) on the pervaporation characteristics of the removal of benzene from an aqueous solution of dilute benzene. When an aqueous solution of 0.05 wt% benzene was permeated through the cross-linked PDMSDMMA (PDMSDMMA–DVF) membranes, they showed a high benzene permselectivity and permeability of these membranes was enhanced with increasing DVF content significantly. The best normalized permeation rate, separation factor for benzene permselectivity, and pervaporation separation index (PSI) of a PDMSDMMA–DVF membrane were 1.72×10 −5 kg m/m 2 h, 4316, and 7423, respectively. The best normalized permeation rate of a PDMSDMMA–DVF membrane was approximately same as the PDMSDMMA membranes cross-linked with other divinyl compounds, but the separation factor and PSI of the former membrane were greater than those of the latter ones. These pervaporation characteristics are discussed from the viewpoint of chemical and physical structure of the cross-linked PDMSDMMA–DVF membranes in detail.

Removal of Benzene from an Aqueous Solution of Dilute Benzene by Various Cross-Linked Poly(dimethylsiloxane) Membranes during Pervaporation

This paper focuses on the effects of cross-linkers of the cross-linked poly(dimethylsiloxane) membranes derived from poly(dimethylsiloxane) dimethyl methacrylate macromonomer (PDMSDMMA), and divinyl compound, on the pervaporation characteristics of the removal of benzene from an aqueous solution of dilute benzene. When an aqueous solution of 0.05 wt % benzene was permeated through the cross-linked PDMSDMMA membranes, they showed high benzene permselectivity. Both the permeability and benzene permselectivity of the membranes were enhanced with increasing divinyl compound content as the cross-linker and were significantly influenced by the kind of divinyl compound. PDMSDMMA membranes cross-linked with divinylsiloxane (DVS) showed very high membrane performance during pervaporation. The best normalized permeation rate, separation factor for benzene permselectivity, and pervaporation separation index of a PDMSDMMA−DVS membrane were 1.96 × 10-5 m kg/(m2 h), 2886, and 5657, respectively. These pervaporation characteristics are discussed from the viewpoint of the chemical and physical structure of the cross-linked PDMSDMMA membranes.

Effects of Morphology of Multicomponent Polymer Membranes Containing Calixarene on Permselective Removal of Benzene from a Dilute Aqueous Solution of Benzene

This paper focuses on the structural characteristics of membranes used in the removal of benzene from a dilute aqueous solution of benzene by pervaporation. Poly(methyl methacrylate)-graft-poly(dimethylsiloxane) (PMMA-g-PDMS) and poly(methyl methacrylate)-block-poly(dimethylsiloxane) (PMMA-b-PDMS) membranes containing tert-butylcalix[4]arene (CA), (CA/PMMA-g-PDMS and CA/PMMA-b-PDMS) were studied. When an aqueous solution of 0.05 wt % benzene was permeated through CA/PMMA-g-PDMS and CA/PMMA-b-PDMS membranes, these membranes showed strong benzene permselectivity. Both the permeability and the benzene permselectivity of CA/PMMA-g-PDMS and CA/PMMA-b-PDMS membranes were enhanced by increasing the CA content, due to the affinity of the CA for benzene. The permeability and the benzene permselectivity of CA/PMMA-b-PDMS membranes were much greater than those of CA/PMMA-g-PDMS membranes. Transmission electron microscope (TEM) observations revealed that both the CA/PMMA-g-PDMS and CA/PMMA-b-PDMS membranes had a micr...

Pervaporation of ethanol/water and benzene/cyclohexane mixtures using novel substituted polyacetylene membranes

In the ethanol/water pervaporation using membranes of Si-containing polymers, poly[1-phenyl-2-(p-trimethylsilyl)phenylacetylene] and poly[1-β-naphthyl-2-(p-trimethylsilyl)phenylacetylene], these polymer membranes permeated ethanol preferentially; αEtOH/H2O 6.86 and 5.30, respectively, at 10 wt% EtOH content in the feed. Membranes of hydrocarbon-based polymers, poly(diphenylacetylene) and poly(1-β-naphthyl-2-phenylacetylene), which were prepared by desilylation of the two Si-containing polymer membranes, also exhibited ethanol permselectivity in ethanol/water pervaporation; αEtOH/H2O 5.95 and 3.79, respectively. Further, in benzene/cyclohexane pervaporation, these desilylated membranes, which were insoluble in any organic solvent, showed rather low benzene permselectivity but very large fluxes. The results of the present study are attributed to the presence of many microvoids and, in turn, sparse structures.

Preparation of photo-induced graft filling polymerized membranes for pervaporation using polyimide with benzophenone structure

The preparation of the composite membranes has been investigated by photo-induced graft filling polymerization. The asymmetric polyimide membranes as substrate were prepared by the phase inversion process using polyimide with benzophenone structure. Graft polymerization took place by UV irradiation supplying monomer, such as methyl acrylate without adding photoinitiator like benzophenone. These graft modified membranes showed benzene permselectivity for benzene/cyclohexane mixture (50/50 v/v) on pervaporation.

Novel Organic-Vycor Glass Composite Membrane Having Si-C Bonds.

A novel organic-ceramic membrane having stable Si-C bonds was developed for separation of high temperature organic solutions. Porous vycor glass was employed for a substrate which was modified by a series of chemical vapor deposition (CVD) and hydrosilylation. 1,3,5,7-Tetramethylcyclotetrasiloxane (H4) was used as a CVD source in order to introduce Si-H bonds on the surface of porous vycor glass. The Si-H bonds were then catalytically hydrosilylated with olefins. As a result, organic functional groups were introduced via Si-C bonds. A compact membrane was obtained when CVD treatment was carried out at 343 K. The membrane that was modified by the hydrosilylation of styrene showed benzene permselectivity in benzene/cyclohexane vapor permeation test at 373 K. The separation factor of benzene over cyclohexane was 2.9 and benzene flux was 1.2 × 10-8 mol m-2s-1Pa-1, and the permeation properties are stable for more than 1000 min at 373 K.

不織布上へのポリイミド非対称膜の作製

The preparation conditions of polyimide (PI) asymmetric membranes on the nonwoven fabric have been investigated. The polyimide membranes were prepared by the phase inversion process in water coagulation bath using the casting solutions composed of polyimide, N, N'-dimethylacetamide (DMAc) as a rich solvent and 1, 4-dioxane (DOx) as a poor solvent. The N2 permeability of polyimide membranes showed 10-5-10-9 [mol/ (m2·s·Pa)]. It was found that polyimide membranes can be utilized as a supporting membrane. And, the polyimide membranes prepared from the casting solution of 25wt% polyimide, 56.3wt% DMAc and 18.7wt% dioxane showed high benzene permselectivity (α =30) for the benzene/ cyclohexane (50vol%/50vol%) solution at 30°C on pervaporation.

Effects of preparation condition of photoinduced graft filling-polymerized membranes on pervaporation performance

Modification of poly(acrylonitrile) membrane was carried out by heterogeneous photoinduced graft polymerization of methyl acrylate from the vapor phase. The technique of transmembrane monomer flow has proved to be effective for filling pores. The effect of preparation conditions like initiator concentration, reaction time and monomer concentration on the membrane separation was investigated. These graft modified membranes showed benzene permselectivity for benzene/cyclohexane mixture (50/50, v/v) on pervaporation.

Pervaporation characteristics of methyl methacrylate-methacrylic acid copolymer membranes ionically crosslinked with metal ions for a benzene/cyclohexane mixture

Methyl methacrylate–methacrylic acid copolymer (MMA–MAA) membranes ionically crosslinked with Fe3+ and Co2+ ions (MMA–MAA–Fe3+ and –Co2+) were prepared, and characteristics of permeation and separation for a benzene/cyclohexane mixture of 50 wt % benzene through these membranes in pervaporation (PV) were studied. Although the introduction of the metal ions to the MMA–MAA membrane enhanced both benzene permselectivity and permeability for a benzene/cyclohexane mixture, the PV characteristics between the MMA–MAA–Fe3+ and –Co2+ membranes were significantly different. The difference in the PV characteristics between these membranes was strongly governed by the difference of these membrane structures based on the glass transition temperature, contact angle to methylene iodide, degree of swelling, and mixture composition absorbed in the membrane, and so on. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 233–241, 1999

Effect of permeation temperature on permeation and separation of a benzene/cyclohexane mixture through liquid‐crystalline polymer membranes

When a benzene/cyclohexane mixture of 10 wt % benzene was permeated through side-chain liquid-crystalline polymer (LCP) membranes by pervaporation at various temperatures, the permeation rate increased with increasing permeation temperature. The LCP membranes also exhibited a benzene permselectivity. The permselectivity for the benzene/cyclohexane mixture through the LCP membrane was different in the glassy, liquid-crystalline, and isotropic states. The LCP membrane had different apparent activation energies for permeation at each state. LCP membrane in the liquid-crystalline state had the highest apparent activation energy of the three states. Results suggest that the benzene permselectivity was influenced by changes in the LCP membrane structure, i.e., a state-transformation. It was found that a balance of the orientation of mesogenic groups and the flexibility of the siloxane chains was very important for benzene permselectivity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 281–288, 1998

Effect of permeation temperature on permeation and separation of a benzene/cyclohexane mixture through liquid-crystalline polymer membranes

When a benzene/cyclohexane mixture of 10 wt % benzene was permeated through side-chain liquid-crystalline polymer (LCP) membranes by pervaporation at various temperatures, the permeation rate increased with increasing permeation temperature. The LCP membranes also exhibited a benzene permselectivity. The permselectivity for the benzene/cyclohexane mixture through the LCP membrane was different in the glassy, liquid-crystalline, and isotropic states. The LCP membrane had different apparent activation energies for permeation at each state. LCP membrane in the liquid-crystalline state had the highest apparent activation energy of the three states. Results suggest that the benzene permselectivity was influenced by changes in the LCP membrane structure, i.e., a state-transformation. It was found that a balance of the orientation of mesogenic groups and the flexibility of the siloxane chains was very important for benzene permselectivity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 281–288, 1998

Pervaporation characteristics of a benzoylchitosan membrane for benzene-cyclohexane mixtures

A benzoylchitosan was synthesized as a membrane material for separation of benzene/cyclohexane mixtures. When the benzoylchitosan membrane was applied to the permeation and separation of benzene/cyclohexane mixtures in pervaporation, both the permeation rate and benzene concentration in the permeate increased with increasing benzene concentration in the feed, and thus this membrane showed benzene permselectivity. Characteristics of permeation and separation of benzene/cyclohexane mixtures through the benzoylchitosan membrane were analyzed by the solution-diffusion model. It was found that the benzene permselectivity was dependent on both the sorption selectivity and diffusion selectivity but was significantly governed by the latter. Also a tentative model for the benzene permselectivity is discussed.

Permeation and separation of [formula omitted] mixtures through cross-linked poly(alkyl methacrylate) membranes

Poly(methyl methacrylate) (PMMA) and poly(ethyl methacrylate) (PEMA) which have strong affinity for benzene were selected as membrane materials and the characteristics of permeation and separation for the benzene cyclohexane mixtures through these poly(alkyl methacrylate) cross-linked with ethylene glycol dimethacrylate (EGDM) membranes by pervaporation were investigated. The cross-linked poly(alkyl methacrylate) membranes exhibited a benzene permselectivity for the benzene cyclohexane mixtures and the permeation rate increased with increasing benzene in the feed solution. The permselectivity of their membranes was strongly governed by the diffusion separation process depending on the difference of the molecular size between the benzene molecule and the cyclohexane molecule. The depression of swelling of those membranes with the increase of the cross-linker content in the benzene cyclohexane mixtures enhanced the benzene permselectivity. This result was attributed to the increase of the selectivity in the sorption separation process with the depression of swelling of the membrane. Furthermore, the cross-linked copolymer (PMMA-PEMA-EGDM) membranes showed excellent benzene permselectivity. These results suggested that both, the increase of affinity of the membrane for benzene and depression of swelling of the membrane, were very important in the separation of the benzene cyclohexane mixtures.

Permeation and separation of benzene/cyclohexane mixtures through liquid-crystalline polymer membranes

The side-chain liquid-crystalline polymer (LCP) was synthesized by the addition of the mesogenic monomer to poly(methylsiloxane) with Pt catalyst. When the benzene/cyclohexane mixtures were permeated through the LCP membranes by pervaporation at various temperatures, the permeation rate increased with increasing benzene concentration in the feed solution and permeation temperature. Though the LCP membranes exhibited a benzene permselectivity, a mechanism of the permeation and separation for the benzene/cyclohexane mixtures was different in the glassy, liquid-crystalline and isotropic state of the LCP membranes. These results suggested that the permselectivity was fairly influenced by the change of the LCP membrane structure, that is, a state transformation. It was found that a balance of the orientation of mesogenic groups and flexibility of siloxane chains is very important for the permeability and selectivity. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 699–707, 1997