Effect of top layer swelling on the oxygen/nitrogen separation by surface modified polyurethane membranes

Cobalt(II) was chelated on the surface of a hydroxyl terminated polybutadiene (HTPB) based polyurethane (PU) membrane. The surface of a HTPB based PU membrane was first modified by ethylenediamine (EA) plasma. The cobalt chelated membrane was prepared by immersing the plasma treated membrane into a cobalt(II)/formamide solution for various length of time. For a fair comparison, the untreated and plasma treated membranes were also immersed in formamide solution. The gas transport properties of all three membranes were compared. Without solvent immersion, the O₂/N₂ selectivity increased from 2.6 to 3.1 after EA plasma treatment. But the permeability decreased from 0.88 GPU to 0.35 GPU. The selectivity was further improved to 4.4 by immersing the plasma treated membrane in a solution of CoCl₂·6H₂O/formamide for 1 h, but the permeability decreased to 0.23 GPU. The solvent immersion had little effect on the transport properties of the untreated membrane. But the transport properties of the plasma treated and cobalt chelated membranes were greatly affected by the formamide immersion. The oxygen and nitrogen permeabilities of the modified top layers could be calculated from a series model for composite membranes. It was found that both the permeability and selectivity of the top layer of the plasma treated membrane increased with the solvent immersing time. For the top layer of the cobalt chelated membrane, the gas permeability first decreased after 1 h immersion and then increased after further immersion in CoCl₂·6H₂O/formamide solution. The selectivity of cobalt chelated membrane increased as the gas permeability decreased and vice versa. These results implied that the EA grafting enhanced the O₂/N₂ selectivity by increasing its oxygen affinity but the cobalt chelating increased the O₂/N₂ selectivity by enhancing the size sieving effect.     

Oxygen/nitrogen separation by polycarbonate/Co(SalPr) complex membranes

An oxygen carrier, cobalt di-(salicylal)-3,3′-diimino-di-n-propylamine (Co(SalPr)), was added into a polycarbonate membrane for improving its oxygen/nitrogen selectivity. Both the oxygen permeability and oxygen/nitrogen selectivity increased when only 3 wt% of Co(SalPr) was added. The permeability kept increasing but the selectivity decreased when more than 3 wt% of Co(SalPr) was added. The oxygen to nitrogen solubility ratio decreased when 3 wt% of Co(SalPr) was added. Further increase in Co(SalPr) content led to an increase in oxygen/nitrogen solubility ratio. It was astonishing to know that the effect of Co(SalPr) content on the oxygen/nitrogen solubility ratio was totally opposite to that on the oxygen/nitrogen selectivity. A membrane gas transport model which combines the dual mobility model with pore model was adopted to explain the above phenomenon. The specific volume measurement implied that the pore diffusion was responsible for this behavior. The contribution of sorption-diffusion type transport was also investigated by examining the transport behavior of the 3 wt% Co(SalPr) containing membrane through which the pore diffusion is relatively low. The effect of upstream pressure on the oxygen permeability and solubility implied that the diffusivity of Henry's mode was much higher than that of Langmuir's mode. It was also found that the effects of upstream pressure and operating temperature on the oxygen/nitrogen selectivity were both in accordance with those on the Henry's mode solubility ratio. The above information suggested that in addition to the pore diffusion the ratio of Henry's mode diffusion dominated the O₂/N₂ separation instead of the overall O₂ to N₂ solubility ratio.     

An improvement on the adhesion‐strength of laminated ultra‐high‐molecular‐weight polyethylene fabrics: surface‐etching/modification using highly effective helium/oxygen/nitrogen plasma treatment

In this study, helium/oxygen/nitrogen (He/O₂/N₂)‐plasma was used to etch/modify the surface of ultra‐high‐molecular‐weight polyethylene (UHMWPE) fiber. After coated with polyurethane (PU), the plasma treated UHMWPE fabrics were laminated. It was found that the values of peeling strength between the laminated UHMWPE fabrics treated with He/O₂/N₂‐plasma were significantly higher (3–4 times) than that between pristine fabrics. The hydrophilic property and the value of the surface roughness of the UHMWPE fibers increased significantly after treated with He/O₂/N₂‐plasma. The mechanism of the oxidation/degradation of the polymers on the surface of the UHMWPE fiber during He/O₂/N₂‐plasma treatment was suggested. In addition, it was found that the higher content of functional groups (carbonyl, aldehyde, and carboxylic acid) on fiber surface and the higher value of surface roughness of the UHMWPE fiber treated with He/O₂/N₂‐plasma could significantly improve the adhesion‐strength of the laminated UHMWPE fabric. Especially, the micro‐aperture on the surface of UHMWPE fiber caused by the strenuous etching of He/O₂/N₂‐plasma treatment was also an important factor on improving the adhesion‐strength between the laminated UHMWPE fabrics. Copyright © 2010 John Wiley & Sons, Ltd.     

Surface modification of polyester by oxygen‐ and nitrogen‐plasma treatment

In this paper, we present a study on the surface modification of polyethyleneterephthalate (PET) polymer by plasma treatment. The samples were treated by nitrogen and oxygen plasma for different time periods between 3 and 90 s. The plasma was created by a radio frequency (RF) generator. The gas pressure was fixed at 75 Pa and the discharge power was set to 200 W. The samples were treated in the glow region, where the electrons temperature was about 4 eV, the positive ions density was about 2 × 10¹⁵ m^?3, and the neutral atom density was about 4 × 10²¹ m^?3 for oxygen and 1 × 10²¹ m^?3 for nitrogen. The changes in surface morphology were observed by using atomic force microscopy (AFM). Surface wettability was determined by water contact angle measurements while the chemical composition of the surface was analyzed using XPS. The stability of functional groups on the polymer surface treated with plasma was monitored by XPS and wettability measurements in different time intervals. The oxygen‐plasma‐treated samples showed much more pronounced changes in the surface topography compared to those treated by nitrogen plasma. The contact angle of a water drop decreased from 75° for the untreated sample to 20° for oxygen and 25° for nitrogen‐plasma‐treated samples for 3 s. It kept decreasing with treatment time for both plasmas and reached about 10° for nitrogen plasma after 1 min of plasma treatment. For oxygen plasma, however, the contact angle kept decreasing even after a minute of plasma treatment and eventually fell below a few degrees. We found that the water contact angle increased linearly with the O/C ratio or N/C ratio in the case of oxygen or nitrogen plasma, respectively. Ageing effects of the plasma‐treated surface were more pronounced in the first 3 days; however, the surface hydrophilicity was rather stable later. Copyright © 2008 John Wiley & Sons, Ltd.     

Separation of nitrogen and oxygen gases by polymeric membrane embedded with magnetic nano‐particle

Asymmetric polyethersulfone (PES) micro‐porous flat sheet membranes were prepared by the phase inversion method (PIM) and used as the support. PES‐PDMS composite membranes were fabricated with coating polydimethylsiloxane on the surface of PES membrane. The FluidMAG‐PAD was coated on PES and PES‐PDMS membrane to prepare super‐paramagnetic membranes for separation of oxygen from nitrogen. Permeance and O₂/N₂ selectivity were evaluated in the absence or presence of external magnetic field. In the absence of external magnetic field, the super‐paramagnetic polymer provides larger surface area leading to extended sites for oxygen adsorption. In the presence of magnetic field, the super‐paramagnetic particles obtained magnetic property leading to a pronounced interaction with oxygen resulting in elevated selectivity and permeability. Copyright © 2011 John Wiley & Sons, Ltd.     

Studies on the macrocycle mediated transport of some metal cations through a bulk liquid membrane system using kryptofix 22

Competitive transport experiments involving Fe⁺³, Cr⁺³, Ni⁺², Co⁺², Ca⁺², Mg⁺² and K⁺ metal cations from an aqueous source phase through some organic membranes into an aqueous receiving phase have been carried out using 4,13-diaza-18-crown-6 (kryptofix 22) as an ionophore present in the organic membrane phase. Fluxes and selectivities for competitive of the metal cations transport across bulk liquid membranes have been determined. A good selectivity was observed for K⁺ cation by kryptofix 22 in 1,2-dichloroethane (1,2-DCE) membrane system. The sequence of selectivity for potassium ion in the organic solvents was found to be: 1,2-DCE > DCM (dichloromethane) >CHCl₃. The transport of K⁺ cation was also studied in the DCM-1,2-DCE, CHCl₃-1,2-DCE and CHCl₃-DCM binary mixed solvents as membrane phase. A non-linear relationship was observed between the transport rate of K⁺ ion and the composition of these binary mixed solvents. The amount of K⁺ transported follows the trend: DCM-DCE > CHCl₃-DCE > CHCl₃-DCM in the bulk liquid membrane studies. Then, the selective transport of K⁺ cation through a DCM-1,2-DCE bulk liquid membrane was studied by kryptofix 22 as an efficient carrier. The highest transport efficiency was obtained by investigating the influence of different parameters such as the concentration of kryptofix 22 in the membrane phase, pH of the source and the receiving phases and the equilibrium time of the transport process. Maximum transport value of 71.62 ± 1.61% was observed for K⁺ ion after 4 hours, when its concentration was 4 × 10^–3 M.     

Metal-ion recognition-competitive bulk liquid membrane transport of transition and post-transition metal cations using a thioether donor acyclic ionophore

The competitive bulk liquid membrane transport of Cr³⁺, Co²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Ag⁺ and Pb²⁺ metal cations with a new synthetic sulfur donor acyclic ligand (pseudo-cyclic ionophore), i.e. 1-(2-[(2-hydroxy-3-phenoxypropyl)sulfanyl]ethylsulfanyl)-3-phenoxy-2-propanol; (C₂₀H₂₆O₄S₂), was examined using some organic solvents as membranes. The membrane solvents include: chloroform (CHCl₃), 1,2-dichloroethane (1,2-DCE), dichloromethane (DCM), nitrobenzene (NB), chloroform-nitrobenzene (CHCl₃-NB) and chloroform-dichloromethane (CHCl₃-DCM) binary mixtures. The transport process was driven by a back flux of protons, maintained by the buffering the source and receiving phases with pH 5 and 3, respectively. The aqueous source phase consisted of a buffer solution (CH₃COOH/CH₃COONa) at pH = 5 and containing an equimolar mixture of these seven metal cations. The organic phase contained the acyclic ligand, as an ionophore and the receiving phase consisted of a buffer solution (HCOOH/HCOONa) at pH = 3. For these systems that displayed transport behaviour, sole selectivity for Ag⁺ cation was observed under the employed experimental conditions in this investigation. The amount of Ag⁺ transported follows the trend: 1,2-DCE > CHCl₃ > DCM > NB in the bulk liquid membrane studies. The transport of the metal cations in CHCl₃-NB and CHCl₃-DCM binary solvents is sensitive to the solvent composition. The influence of the stearic acid, palmitic acid and oleic acid in the membrane phase on the ion transport was also investigated.     

STUDIES ON THE PERMEABILITY OF P VC/EBBA OVERLAPPED ULTRATHIN COMPOSITE MEMBRANES MODIFIED BY PLASMA-POLYMERIZATION WITH FLUOROCARBON MONOMERS

The PVC/EBBA ultrathin composite membranes with thickness of about 100 nm were prepared by spreading the solution on water surface. The overlapped composite membrane showed a characteristic aggregation structure in which the polymer matrix exists as a three-dimensional spongy network and the liquid crystal domains werc observed. Tne surface modification for the overlapped membranes was carried out by means of plasma-polymerization with the monomers of fluorocarbon compounds. Both Arrhenius plots of permeability coefficients for oxygen ((?)_O_2) in the membrane samples before and after modification showed significant increase in the vicinity of the T_(KN) of EBBA.     

Tailoring the surface chemistry of carbon fiber and E‐glass composites for improved adhesion

The main challenges in the manufacture of composite materials are low surface energy and the presence of silicon‐containing contaminants, both of which greatly reduce surface adhesive strength. In this study, carbon fiber (CF) and E‐glass epoxy resin composites were surface treated with the Accelerated Thermo‐molecular adhesion Process (ATmaP). ATmaP is a multiaction surface treatment process where tailored nitrogen and oxygen functionalities are generated on the surface of the sample through the vaporization and atomization of n‐methylpyrrolidone solution, injected via specially designed flame‐treatment equipment. The treated surfaces of the polymer composites were analyzed using XPS, time of flight secondary ion mass spectrometry (ToF‐SIMS), contact angle (CA) analysis and direct adhesion measurements. ATmaP treatment increased the surface concentration of polar functional groups while reducing surface contamination, resulting in increased adhesion strength. XPS and ToF‐SIMS showed a significant decrease in silicon‐containing species on the surface after ATmaP treatment. E‐glass composite showed higher adhesion strength than CF composite, correlating with higher surface energy, higher concentrations of nitrogen and C?O functional groups (from XPS) and higher concentrations of oxygen and nitrogen‐containing functional groups (particularly C₂H₃O⁺ and C₂H₅NO⁺ molecular ions, from ToF‐SIMS). Copyright © 2010 John Wiley & Sons, Ltd.     

Improved Surface and Adhesion Properties of Wood-Polyethylene Composite by Treatment with Argon–Oxygen Low Pressure Plasma

Ar:O₂ low pressure plasma (Ar:O₂ LPP) surface treatment is proposed for increasing the surface energy and improve the adhesion of wood-polyethylene composite. The treatment time was varied between 20 and 90 s and the configuration of the shelves inside the plasma chamber (direct and secondary downstream) was also changed. Ar:O₂ LPP treatment during 30–40 s created new surface carbon–oxygen groups, increased the surface energy, mainly its polar component, reduced roughness and caused ablation of wood-polyethylene composite, irrespective of the configuration of the shelves inside the plasma chamber. The increase of the treatment time above 40 s did not cause additional surface modifications. Adhesion of the wood-polyethylene composite was noticeably increased when was treated with Ar:O₂ LPP. The surface modifications of Ar:O₂ LPP treated wood-polyethylene composite were partially lost during 24 h after treatment.     

Competitive transport of seven metal cations through bulk liquid membrane using 5,12-di(phenoxymethyl)-1,4-dioxa-7, 10-dithiacyclododecane-2,3-dione as carrier

The competitive metal ion transport of copper(II), cobalt(II), zinc(II), cadmium(II), silver(I), chromium(III) and lead(II) with a S-O donor compound was examined. Competitive transport experiments involving the metal cations from an aqueous source phase through an organic membrane into an aqueous receiving phase have been carried out using 5,12-di(phenoxymethyl)-1,4-dioxa-7,10-dithiacyclododecane-2,3-dione as the ionophore present in the organic phase. Fluxes and selectivities for competitive metal cations transport across bulk liquid membranes have been determined in a variety of chlorinated hydrocarbon and aromatic hydrocarbon solvents. The membrane solvents include: dichloromethane (DCM), chloroform (CHCl₃), 1,2-dichloroethane (1,2-DCE), and nitrobenzene (NB) and also in chloroform-dichloromethane (CHCl₃-DCM) and chloroform-nitrobenzene (CHCl₃-NB) binary mixtures. Although the selectivity for silver(I) cation in all of these organic solvents is fundamentally similar, but the most transport rate for Ag(I) was obtained in dichloromethane. The sequence of transport rate for silver ion in organic solvents was: DCM > CHCl₃ > 1,2-DCE > NB. A linear relationship was observed between the transport rate of silver ion and the composition of CHCl₃-DCM, but a non-linear behavior was observed in the case of CHCl₃-NB binary solution. The influence of the stearic, palmetic and oleic acids as surfactant in the membrane phase on the transport of the metal cations was also investigated.     

Sorption and transport mechanism of gases in polycarbonate membranes

The transport phenomena of oxygen and nitrogen across a pure polycarbonate (PC) and a cobalt(III) acetylactonate (Co(acac)₃) containing PC membrane was studied. Co(acac)₃ was added into a polycarbonate membrane to enhance its oxygen solubility. The oxygen sorption isotherms was measured. It was found that the oxygen solubility decreased sharply as pressure increased, especially at low pressure region. On the contrary, the oxygen permeability increased slightly with respect to pressure. Both the solution-diffusion model and traditional dual mobility model were unable to explain the inconsistent pressure dependency between solubility and permeability. Instead of adopting Langmuir-Henry sorption model, a modified dual mobility model which incorporates BET-type isotherm to describe oxygen sorption. The diffusivity of molecules moving at the first adsorbed layer was assumed to be different from those moving at higher layers. This modified dual mobility model satisfactorily described both the pressure dependency of oxygen solubility and permeability. It was also found that the increase of oxygen/nitrogen selectivity was not due to the elevation of oxygen to nitrogen solubility ratio but due to the mobility ratio of oxygen to nitrogen at the higher adsorption layers.     

Adhesion Enhancement and Characterization of Plasma Polymerized 1,2-Dichloroethane on Polypropylene Surface

Polypropylene (PP) films were modified in 1,2-dichloroethane (DCE) plasma. Surface energy measurement and rate of deposition showed two-step surface modification. First, incorporation of chloride ions on PP surface followed by deposition of cross-linked layer. DCE plasma modified PP films were subsequently compared with earlier reported work on carbontetrachloride (CCl₄) and chloroform (CHCl₃) plasma modification. Modified films were characterized using ATR-FTIR technique by monitoring the relative changes in intensities of C–H stretch vibrations. The nature of deposition on PP film was characterized using FTIR technique and solubility test. Peel strength measurements of DCE, CCl₄, and CHCl₃ plasma modified films showed improvement in bonding strength. Durability of plasma modified PP film was studied by calculating surface energy and peel strength of samples aged for two months.     

Surface Modification and Characterization of Dichloromethane Plasma Treated Polypropylene Film

Surface of polypropylene (PP) film was modified in plasma of dichloromethane (CH₂Cl₂). The nature of surface modifications and formation of cross-linked layer due to plasma polymerization was studied by surface energy measurements and solubility test. Surface modification achieved by CH₂Cl₂ plasma was compared with the reported work on chloroform (CHCl₃) and carbontetrachloride (CCl₄) plasma modifications. Modified surface characterized by ATR-FTIR technique indicated formation of saturated and unsaturated cross-linked product. On the basis of relative intensity change of the specific bands, the site of attachment of chlorine on PP surface was investigated. Adhesive strength of modified film was measured by T-peel test method. Stability of modified surface was studied by measuring surface energy and peel strength after two months.     

介孔CuO/γ-Al2O3催化剂的 制备及其在合成气制二甲醚反应中的应用

以三嵌段共聚物F₁₂₇为模板剂,以异丙醇铝、硝酸铜为原料,采用溶剂挥发自组装法制备具有介孔结构的CuO/γ-Al₂O₃复合催化剂.通过XRD、SEM-EDS、H₂-TPR、N₂-吸附脱附、TEM等技术对该催化剂的结构进行了表征.实验结果表明,通过溶剂挥发自组装法制备的催化剂CuO/γ-Al₂O₃具有有序的介孔结构,并且具有较大的比表面积以及均一的介孔结构,并且Cu元素均匀地分布在γ-Al₂O₃的表面.将该复合催化剂用于合成气直接制备二甲醚的反应,在空速1 500 h^-1、温度320 ℃、压力5 MPa的条件下,CO转化率最高达到68.8%、DME选择性达到59.0%.连续反应50 h后,CO转化率从68.8%降低至59.5%,DME选择性基本保持不变,催化剂部分失活的原因是由于铜元素部分发生了聚集.     

掺杂纳米SiO2的PVDF-g-PSSA质子交换膜

以聚偏氟乙烯(PVDF)为骨架, 采用溶液接枝苯乙烯磺酸, 合成了掺杂纳米SiO₂颗粒的复合质子交换膜(PVDF/xSiO₂-g-PSSA). 利用红外光谱、热失重分析方法、扫描电镜, 对膜的结构、热稳定性、表面及断面形态进行了表征. 考察了膜的吸水率、电导率、甲醇渗透性等性质. 结果表明, 纳米SiO₂颗粒能提高膜的阻醇性能, 掺杂质量分数10%的适量SiO₂颗粒所得的复合膜的甲醇渗透系数达1.0×10^－7 cm²/s, 低于聚偏氟乙烯接枝苯乙烯磺酸(PVDF-g-PSSA)膜的1.7×10^－7 cm²/s, 仅为Nafion-117的渗透系数的二十分之一. PVDF/10% SiO₂-g-PSSA复合膜具有较高的选择性, 在直接甲醇燃料电池中具有良好的应用前景.     

Modification of porous poly(ether sulfone) membranes by low‐temperature CO2‐plasma treatment

A general method of modifying the entire cross section of porous poly(ether sulfone) membranes with a low‐temperature CO₂‐plasma treatment is reported. Both surfaces of the membranes are highly hydrophilic, with a water drop on the surface disappearing in less than 1 s, even 6 months after plasma treatment. This high hydrophilicity of both membrane surfaces results from the incorporation of hydrophilic functionalities, as evidenced by Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy. The incorporation of these hydrophilic functionalities takes place primarily during plasma treatment, with some incorporation of atmospheric oxygen and nitrogen immediately upon exposure to air. Scanning electron microscopy shows that the membrane surface is covered by a thin, white layer that is likely the result of etching and redeposition of sputtered surface fragments. An increase in the water bubble point and glass‐transition temperature is also observed for CO₂‐plasma‐treated membranes. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2473–2488, 2002     

Preparation of CO_2 selective composite membranes using Pebax/CuBTC/PEG-ran-PPG ternary system

Three phase Pebax~? MH 1657/PEG-ran-PPG/CuBTC(polymer/liquid/solid) was successfully deposited as a selective layer on a porous Polysulfone(PSF) support. In fact, the beneficial properties of PEG(high selectivity) with those of PPG(high permeability, amorphous) have been combined with superior properties of mixed matrix membrane(MMMs). The membranes were characterized by DSC, TGA and SEM, while CuBTC was characterized by CO_2 and CH_4adsorption test. Statistically based experimental design(central composite design, CCD) was applied to analyze and optimize the effect of PEG-ran-PPG(10–50 wt%) and CuBTC(0–20 wt%) mass contents on the CO_2 permeance and CO_2/CH_4 ideal selectivity. Based on the regression coefficients of the obtained models, the CO_2 permeance was notably influenced by PEG-ran-PPG,while CuBTC has the most significant effect on the CO_2/CH_4 ideal selectivity. Under the optimum conditions(PEG-ran-PPG: 32.76 wt% and CuBTC: 20 wt%), nearly 620% increase in the CO_2 permeance and43% enhancement in the CO_2/CH_4 ideal selectivity was observed compared to the neat Pebax. The effect of pressure(3, 9 and 15 bar) on the pure and mixed gas separation performance of the composite membranes was also investigated. The high solubility of CO_2 in the membranes resulted in the enhancement of CO_2 permeability with increase in gas pressure.     

Vanadium Chloroperoxidases: The Missing Link in the Formation of Chlorinated Compounds and Chloroform in the Terrestrial Environment?

It is well established that the majority of chlorinated organic substances found in the terrestrial environment are produced naturally. The presence of these compounds in soils is not limited to a single ecosystem. Natural chlorination is also a widespread phenomenon in grasslands and agricultural soils typical for unforested areas. These chlorinated compounds are formed from chlorination of natural organic matter consisting of very complex chemical structures, such as lignin. Chlorination of several lignin model compounds results in the intermediate formation of trichloroacetyl‐containing compounds, which are also found in soils. These decay, in general, through a haloform‐type reaction mechanism to CHCl₃. Upon release into the atmosphere, CHCl₃ will produce chlorine radicals through photolysis, which will, in turn, lead to natural depletion of ozone. There is evidence that fungal chloroperoxidases able to produce HOCl are involved in the chlorination of natural organic matter. The objective of this review is to clarify the role and source of the various chloroperoxidases involved in the natural formation of CHCl₃.     

Ionic liquid immobilization on carbon nanofibers and zeolites: Catalyst design for the liquid-phase toluene chlorination

The environmental-friendly chlorination reaction of toluene by trichloroisocyanuric acid (TCCA, C₃N₃O₃Cl₃) was investigated applying immobilized ionic liquids (ILs) on different supports. Ionic liquids were grafted either on carbon nanofibers (CNF) or encapsulated in zeolites. Their influence on the chlorination activity as well as on the selectivity in different chlorinated products was studied. An unusually high selectivity toward meta-chlorotoluene was achieved, up to 36%. Hence, the selectivity could be tuned to produce either expected ortho-/para-chlorotoluene or meta-chlorotoluene with a proper support choice.