Hydrophobic modification of SAPO-34 membranes for improvement of stability under wet condition

SAPO-34 zeolite membranes show high efficiency for CO2/CH4 separation but suffer from the reduction of separation performance when exposed to humid atmosphere.In this work,n-dodecyltrimethoxysilane(DTMS)was used to modify the hollow fibers supported SAPO-34 membranes to increase the external surface hydrophobicity and thus sustain their performance under moisture environment.The modified membranes were fully characterized.Their separation performance was extensively investigated in both dry and wet gaseous systems and compared with the un-modified ones.The un-modified SAPO-34 membrane exhibited a high separation selectivity of 160 and CO2 permeance of 1.18×10-6 mol·m-2·s-1·Pa-1 for separation of dry CO2/CH4 at 298 K.However,its separation selectivity declined to 0.9 and the CO2 permeance was only about 1.7×10-8 mol·m-2·s-1·Pa-1 for wet CO2/CH4 at same temperature.High temperature(e.g.353 K)could reduce the effect of moisture to improve SAPO-34 separation selectivity,but further increasing temperature(e.g.373 K)led to decrease in CO2/CH4 separation selectivity.A significant decrease of selectivity was observed at higher pressure drop.The modified SAPO-34 membrane showed decreased CO2 permeance but increased separation selectivity for dry CO2/CH4 gas mixture,and super performance for wet CO2/CH4 gas mixture due to the improved hydrophobicity of membrane surface.A separation selectivity of 65 and CO2 permeance of 4.73×10-8 mol·m-2·s-1·Pa-1 for wet CO2/CH4 mixture can be observed at 353 K with a pressure drop of 0.4 MPa.Furthermore,the modified membrane exhibited stable separation performance during the 120-hour test for wet CO2/CH4 mixture at 353 K.The hydrophobic modification paves a way for SAPO-34 membranes in real applications.

Removal of 2,4-dichlorophenol from wasterwater by vacuum membrane distillation using hydrophobic PPESK hollow hiber membrane

2,4-Dichlorophenol was removed from wasterwater using a new hydrophobic poly（phthalazinone ether sulfone ketone） （PPESK） hollow fiber membrane by vacuum membrane distillation （VMD）.

Monitoring the spontaneous wetting process of hydrophobic microporous membrane assisted by alternating current impedance spectroscopy

In the process of membrane absorption,spontaneous wetting of hydrophobic microporous membrane causes membrane modification and increases membrane phase mass transfer resistance,which have attracted wide interest.However,due to the limitations of previous testing methods,the study of the spontaneous membrane wetting process is limited.Herein,we present a method for monitoring spontaneous membrane wetting by measuring its alternating current(AC)impedance.The impedance tests of the PVDF flat membranes and hollow fiber membranes were conducted in a two-electrode system.The results of equivalent circuit fitting indicate that the impedance value of the unwetted membrane is about 1.02×10^(10)Ω,which is close to the theoretical value of 1.4×10^(10)Ω,and this method can quantify the electrochemical impedance value of membranes with different degrees of spontaneous wetting.In addition,a method of impedance test for real-time monitoring of spontaneous wetting was designed.During the experiment,the timeliness and continuity of this method are confirmed with exact judgment under different conditions.In future work,the impedance data will be used to build model to predict the percentage of membrane wetting degree.

Preparation of hydrophobic flat sheet membranes from PVDF-HFP copolymer for enhancing the oxygen permeance in nitrogen/oxygen gas mixture

In this study, poly(vinilydene fluoride-co-hexafluoropropylene)(PVDF-HFP) was used for preparation of hydrophobic membranes using non-solvent induced phase inversion(NIPS) technique. PVDF-HFP copolymer with concentrations of 10 wt% and 12 wt% was prepared to investigate the effect of polymer concentration on pore structure,morphology, hydrophobicity and performance of prepared membranes. Besides, the use of two coagulation baths with the effects of parameters such as coagulant time, polymer type and concentration, and the amount of nonsolvent were studied. The performance of prepared membranes was evaluated based on the permeability and selectivity of oxygen and nitrogen from a gas mixture of nitrogen/oxygen under operating conditions of feed flow rate(1–5 L·min-1), inlet pressure to membrane module(0.1–0.5 MPa) and temperatures between 25 and 45 °C. The results showed that the use of two coagulation baths with different compositions of distillated water and isopropanol,coagulant time, polymer type and concentration, and the amount of non-solvent additive have the most effect on pore structure, morphology, thickness, roughness and crystallinity of fabricated membranes. Porosity ranges for the three fabricated membranes were determined, where the maximum porosity was 73.889% and the minimum value was 56.837%. Also, the maximum and minimum average thicknesses of membrane were 320.85 μm and115 μm. Besides, the values of 4.7504 × 10-7 mol· m-2· s-1· Pa-1, 0.525 and 902.126 nm were achieved for maximum oxygen permeance, O2/N2 selectivity and roughness, respectively.

Removal of Endotoxin from Human Serum Albumin Solutions by Hydrophobic and Cationic Charged Membrane

A novel matrix of macropore cellulose membrane was prepared by chemical graft, and immobilized the cationic charged groups as affinity ligands. The prepared membrane Fan be used for the removal of endotoxin from human serum albumin (HSA) solutions. With a cartridge of 20 sheets affinity membrane of 47 mm diameter, the endotoxin level in HSA solution can be reduced ro 0.027 eu/mL. Recovery of HSA was over 95%.

Temperature-induced hydrophobicity transition of MXene membrane for directly preparing W/O emulsions

Although hydrophilic membranes are desired for reducing resistance to water permeation, hydrophilic surfaces are not used in the water-in-oil(W/O) membrane emulsification process because water spreads on the hydrophilic surface without forming droplets. Here, we report that a hydrophilic ceramic membrane can form a hydrophobic interface in diesel at a higher temperature;interestingly, the experiments show that the contact angle increases when the temperature rises. The hydrophilic membrane surface evolves into a hydrophobic interface, particularly near the boiling point of water, resulting in a water contact angle of 147.5° ± 1.2°. This work established a method for preparing W/O monodispersed emulsions by direct emulsification of hydrophilic ceramic membranes at a temperature close to the boiling point of water.Additionally, it made high flux of membrane emulsification of monodispersed W/O emulsions possible,which satisfied the industrial requirements of fluidized catalytic cracking in the petrochemical industry.

Carbon Capture from Flue Gas Based on the Combination of Non-Contact Hydrophobic Porous Ceramic Membrane and Bubbling Absorption

A hybrid system combined with a non-contact membrane and bubbling absorption is proposed to capture CO_(2) from flue gas.The non-contact way of membrane and liquid absorbent effectively avoids the reduction of gas diffusion flux through the membrane.High-porosity ceramic membranes in hybrid systems are used for gas-solid separation in fuel gas treatment.Due to the high content of H_(2)O and cement dust in the flue gas of the cement plant,the membrane is hydrophobically modified by polytetrafluoroethylene(PTFE)to improve its anti-water,anti-fouling,and self-cleaning performances.The results show that the diffusion flux of CO_(2) through the membrane is still higher than 7.0×10^(−3) mol/m^(2)s(20%CO_(2) concentration)even under the influence of water and cement dust.In addition,slaked lime selected as the absorbent is cheap and the product after bubbling absorption is nano-scale light calcium carbonate.To sum up,the hybrid system combining non-contact membrane and bubbling absorption is expected to be used to capture carbon dioxide from the flue gas of the cement plant.

Selective recovery of Cu(Ⅱ) through polymer inclusion membranes mediated with 2-aminomethylpyridine derivatives

The Cu(Ⅱ) separation behaviors with polymer inclusion membranes(PIMs) are explored by modifying 2-aminomethylpyridine derivatives with hydrophobic alkyl chains, including 2-[N-(tert-butyloxycarbonylmethyl)-2-picolyamino]acetate(AMB), N,N-dioctyl-2-aminomethylpyridine(AMD), tert-butyl 2-(N-octyl-2-picolyamino) acetate(AMC), and N,N-didecyl-2-aminomethylpyridine(AME). The transport flux and selectivity of Cu(Ⅱ) are determined by optimizing composition and structure of carriers and plasticizers. The results show that the hydrophobic modification of 2-aminomethylpyridine derivatives can boost the selective transport of copper ions in PIMs and membrane stability. In the optimum composition of 30 wt.% PVC, 30 wt.% AME, and 40 wt.% NPOE, the initial flux of Cu(Ⅱ) is 5.8×10^(−6) mol·m^(−2)·s^(−1). The FT-IR and XPS spectra identify that the alkyl amine functional groups of AME involve in the transport of copper chloride species. The SAXS analysis demonstrates that the generated micro-channels in PIMs induced by the hydrophobic modification of 2-aminomethylpyridine derivatives can contribute to the enhanced Cu(Ⅱ) flux.

Novel nanofiltration membranes with tunable permselectivity by polymer mediated phase separation in polyamide selective layer

Microstructure in selective layer has played a decisive role in permselectivity of nanofiltration(NF) membranes,and nanomaterials were well-known additives that had been applied to mediate the microstructure and permeability of polyamide NF membranes. However, nanoadditives generally displayed a poor dispersion in membranes or in fabrication process. To solve this problem, we showed an interesting concept that novel NF membranes with hybrid selective layer consisting of flexible polyisobutylene(PIB) and rigid polyamide could be fabricated from well-defined interfacial polymerization. The hydrophobic polymer mediated phase separation and microdomains formation in polyamide layer were found. The immiscibility between the rigid polyamide and flexible PIB as well as the resultant interface effect was interpreted as the reason for the polymer enhanced permselectivity, which was similar with the well-known thin film nanocomposite(TFN) membranes that nanoparticles incorporated contributed significantly to membrane permeability and rejection performance.Our results have demonstrated that novel NF membranes with enhanced performance can be prepared from immiscible polymers, which is a new area that has not been extensively studied before.

Interaction of CORM-2 with hydrophobic sites: Beyond CO

Carbon monoxide releasing molecules (CORMs) have been recently developed for research and pharmacological purposes. A considerable amount of studies demonstrated a wide spectrum of biological activities for lipophilic CORM-2 (tricarbonyldichlororuthenium (II) dimer). It is generally accepted that the liberated gas provides the specific activities to CORMs, with a little attention paid to any possible effect of complementary core molecules. However, the versatile repertoire of actions attributed to CORM-2 is surprisingly wide for CO, a molecule with the sole chemical activity of binding to ferrous iron in protein prosthetic groups. The study was designed to analyze CORM-2 and its core molecule (“i”CORM) activities at a molecular level. With respect to the hydrophobic nature of the compounds, we followed their interactions with several amphipathic entities: the heme sites of hemoproteins, heme binding proteins and cell membranes. CORM-2/“i”CORM decreased the Soret optical density of hemoglobin and myoglobin, indicating that both compounds interact with the protein amphipathic site in the heme pocket. Pre-addition of CORM-2/“i”CORM to the apo-forms of the plasma heme binding proteins, hemopexin and albumin, partially abolished their heme binding capacity. In contrast, the compounds had no effect on the preformed heme-protein complexes. Addition of CORM-2/“i”- CORM to blood or isolated erythrocytes revealed aggregation of the cells or lysis, depending on the rea-gent-to-cells ratio. It was concluded that the ruthenium containing core molecule of CORM-2 may be physiologically active due to non-specific hydrophobic interactions. As each type of CORMs is expected to have a different mode of action beyond CO activity, their potential therapeutic uses will require clarification.

Preparation and Characterization of PVC/PAN Membrane Used as Medical Exhaust Membranes

The wet phase inversion process was used to prepare a kind of medical exhaust membranes with super-hydrophobicity and good gas permeability capacity by using non-woven fabric as the support base.The influences of solution temperature,the evaporation time,the content of the non-solvent additive and the ratio of polyvinyl chloride(PVC)/polyacrylonitrile(PAN) on the gas permeability capacity and hydrostatic pressure of the resultant membranes were investigated.A kind of composite membrane with gas permeability about 2 800 mL/min and hydrostatic pressure of 36 kPa was obtained.In addition,the relationship between the properties and structure of the membrane was analyzed.

Hydrophobic polyethersulfone porous membranes for membrane distillation

Membrane distillation （MD） is a thermal, vapor-driven transportation process through micro porous hydrophobic membranes that is increasingly being applied to seawater and brine desalination processes. Two types of hydrophobic microporous polyethersulfone fiat sheet membranes, namely, annealed polyethersulfone and a polyethersulfone/tetraethoxysilane （PES/TEOS） blend were prepared by a phase inversion process. The membranes were characterized and their performances were investigated using the vacuum membrane distillation of an aqueous NaCI solution. The performances of the prepared membranes were also compared with two commercially available hydrophobic membranes, polyte- trafluorethylene and polyvinylidene fluoride. The influence of operational parameters such as feed temperature （25-65 ℃）, permeate vacuum pressure （200 800 mbar）, feed flow rate （8-22 mL/s） and feed salt concentration （3000 to 35000 mg/L） on the MD permeation flux were investigated for the four membranes. The hydrophobic PES/TEOS membrane had the highest salt rejection （99.7%） and permeate flux （86 kg/（m^2 -h）） at 65 ℃, with a feed of 7000 ppm and a pressure of 200 mbar.

Fabrication and characterization of affordable hydrophobic ceramic hollow fibre membrane for contacting processes

Affordable hydrophobic hollow fibre membranes were prepared using kaolin and alumina based ceramic powders via a combined phase inversion and sintering technique,followed by a grafting with fluoroalkylsilane(FAS).The crux of the matter in this paper is to study the changes in the properties of the hollow fibre membranes(gas permeation,mechanical strength,pore size,porosity,tortuosity,morphology,and contact angle)by the addition of alumina(Al2O3)to the pure kaolin with mono or multiparticle sizes.By varying the overall loading and particle size of alumina addition,different morphologies of the membranes were obtained due to the differences in the path lengths during phase inversion process for each solvent and nonsolvent exchange.The successful grafting with FAS was evidenced by the increase in contact angle from nearly equal to zero degree before grafting to 140°after grafting.Kaolin-alumina-4,one of the hollow fibres fabricated in this work,achieved a mean pore size of 0.25μm with the bending strength of 96.4 MPa and high nitrogen permeance of 2.3×10^(-5) mol·m^(-2)·Pa^(-1)·s^(-1),which makes the hollow fibre most suitable for the membrane contactor application.

Hydrophobic interaction membrane chromatography for bioseparation and responsive polymer ligands involved

Hydrophobic interaction chromatography （HIC） is a rapid growing bioseparation technique, which separates biomolecules, such as therapeutic proteins and antibodys, based on the reversible hydrophobic interaction between immobilized hydrophobic ligands on chromatographic resin spheres and non-polar regions of solute molecule. In this review, the fundamental concepts of HIC and the factors that may affect purification efficiency of HIC is summarized, followed by the comparison of HIC with affinity chromatography and ion-exchange chromatography. Hydrophobic interaction membrane chromatography （HIMC） combines the advantages of HIC and membrane process and has showed great potential in bioseparation. For better understanding of HIMC, this review presents an overview of two main concerns about HIMC, i.e. membrane materials and hydrophobic ligands. Specifically, cellulose fiber-based membrane substrate and environment-responsive ligands are emphasized.

Highly hydrophobic oil−water separation membrane: reutilization of waste reverse osmosis membrane

The increasing applications of seawater desalination technology have led to the wide usage of polyamide reverse osmosis membranes,resulting in a large number of wasted reverse osmosis membranes.In this work,the base nonwoven layer of the wasted reverse osmosis membrane was successfully modified into the hydrophobic membrane via surface deposition strategy including TiO_(2) and 1H,1H,2H,2H-perfluorooctyltrichlorosilane(PFOTS),respectively.Various techniques were applied to characterize the obtained membranes,which were then used to separate the oil–water system.The optimally modified membrane displayed good hydrophobicity with a contact angle of 135.2°±0.3°,and its oil–water separation performance was as high as 97.8%.After 20 recycle tests,the oil–water separation performance remained more than 96%,which was attributed to the film adhesion of the anchored TiO_(2) and PFOTS layer on the surface.This work might provide a new avenue for recycling the wasted reverse osmosis membrane used in oily wastewater purification.

疏水α-Al_(2)O_(3)陶瓷膜特性表征及温差驱动能力研究

疏水陶瓷膜在膜蒸馏领域具有突出优势,可拓宽膜蒸馏应用场景.采用新方法制备疏水α-Al_(2)O_(3)陶瓷膜,表征形貌特征、疏水性能、接枝有效性及宽温域热稳定性,揭示温差对单位温差驱动能力的影响规律,测定疏水陶瓷膜蒸馏过程的离子截留率.研究结果表明:疏水陶瓷膜表面形成了较规律的粗糙结构,疏水性能优异;疏水陶瓷膜表面的1H,1H,2H,2H-全氟癸基三乙氧基硅烷发挥了疏水作用,且具有较好的高温热稳定性;基于原水温度的单位温差驱动能力(e_(c))随温差(ΔT)按-0.7356次幂函数规律负相关变化,而基于冷却水温度的单位温差驱动能力(e_(r))随ΔT按1.74589次幂函数规律正相关变化;疏水陶瓷膜蒸馏过程对所有被测离子的截留率均大于99.96%.该研究对指导制定疏水陶瓷膜蒸馏运行策略具有重要意义.

中空纤维膜臭氧接触式反应器传质机理分析

将疏水性聚四氟乙烯(PTFE)中空纤维膜组装成膜接触器,开发了膜接触式臭氧(O_(3))传质技术。对比了气泡传质和膜接触传质的差异,通过O_(3)传质模型和阻力模型对该技术的主要影响因素和传质机理进行了研究。结果表明,O_(3)可以有效地通过疏水性PTFE膜进行传质,当搅拌速度达到1500r/min时,膜传质的表观传质系数(0.3049min-1)与气泡传质(0.3109min-1)相当。同时,膜表面的疏水结构将尾气的湿度降低到0.8g/m^(3)以下,远低于气泡传质(>11.5g/m^(3)),符合进入臭氧发生器的标准,具备回收氧气的可行性。O_(3)的传质通量受液体流速、p H、污染物浓度、气体流量以及进气O_(3)浓度的影响。在pH=11、苯酚浓度为0或pH=7、苯酚浓度为20mg/L时,传质通量达到了0.16g/(m^(2)·h)。O_(3)传质过程的传质阻力主要由膜阻力和液相阻力组成,而通过液相条件控制可以有效减小液相阻力,因此进一步降低传质阻力需要膜技术的发展。

热泵-减压膜蒸馏工艺优化及能效分析

针对热泵-膜蒸馏过程中热量不平衡问题展开试验研究,采用两支减压膜蒸馏组件并入料液循环流路,使其分别发挥热量回收及排放富余热量的作用,实现热泵系统的热量平衡.通过试验测试,显示MD1200和MD200被认为是最佳双膜组合.采用该双膜组合进行连续8 h的含盐料液处理,结果显示,双膜组合可以获得稳定、连续的膜蒸馏运行效果,总产水量平均为1.9 L/h,系统比能耗最高310 W·h/kg产水,能耗性能优于无热量回收的膜蒸馏工艺,与已工业化的多效膜蒸馏工艺相当,有望成为可获得工业应用的低能耗膜蒸馏新工艺.