CVD法制备Sn掺杂MFI分子筛膜及其对乙醇/水体系的分离性能

采用化学气相沉积(CVD)法对MFI分子筛膜进行Sn掺杂, 制备了一种Sn-MFI分子筛膜, 并研究了其渗透汽化分离乙醇/水体系的性能. XRD, ²⁹Si NMR, UV-Vis及分离实验结果表明, 采用CVD法在将Sn引入MFI膜时, 膜层结构基本得到保持, Sn可以进入分子筛骨架, 有效地减少了膜表面的硅羟基缺陷, 提高了膜分离乙醇/水体系时的稳定性. 在SnCl₄用量为3 mL、 修饰时间为1 h时, 所得到的Sn-MFI分子筛膜的渗透汽化分离性能最佳, 并可在60 ℃下分离5%(质量分数)乙醇/水混合物时保持良好的稳定性. 在经过连续50 h渗透气化分离后, 其渗透通量仅从1.52 kg·m^-2·h^-1下降至1.38 kg·m^-2·h^-1, 分离因子从18下降至16.     

Biologically inspired silk fibroin grafted polyacrylonitrile filtration membrane prepared in ZnCl2 aqueous solution

Biologically inspired silk fibroin grafted polyacrylonitrile (SF-g-PAN) filtration membrane was prepared using ZnCl₂ aqueous solution as solvent, avoiding the use of organic solvents.     

Water-alcohol Separation by Pervaporation through Zeolite Modified Poly(amidesulfonamide)s (PASAs)

A series of poly(amidesulfonamide)s (PASAs) which have been synthesized in our laboratory possess good membrane fabrication properties^[1]. The potential use of these membrane materials in RO, UF and PV were demonstrated^[2,3]. Reminiscent to the PV performance of other glassy polymers, most of these materials exhibit a fairly high separation factor albeit a permeation flux below 35 g m^-2 h^-1 in the PV separation of aqueous alcohol mixtures. To have a real application prospect in PV, the permeation flux through the membranes has to e further improved. The present work represents our effort to upgrade the separation characteristics of PASAs by blending with inert hydrophilic zeolites. Three types of PASAs (structure shown in Figure 1) were selected to be fabricated by blending different amount of zeolite NaA or NaX. The zeolite filled membranes were characterized by SEM, IR spectroscopy, sorption measurements and wide-angle X-ray diffraction. By adding proper amount of NaA into the polymer casting solutions, the resultant zeolite filled membranes exhibited improvement in both selectivity and permeability in the separation of 10% aqueous solutions of ethanol, propan-l-ol and propan-2-ol, as compared to the zeolite free membrane (Table 1).     

MFI型分子筛膜的两段变温合成及对二甲苯异构体的分离性能

分别采用恒温和变温两种方法在氧化铝支撑体上原位制备了MFI型分子筛膜. 恒温法合成的MFI型分子筛膜晶体颗粒较大, 在高温脱除模板剂时会形成较大的缺陷, 没有对二甲苯/邻二甲苯(PX/OX)分离性能. 变温法合成的MFI型分子筛膜晶体在a, b方向尺寸较小, 在高温脱除模板时不会形成较大缺陷, 对PX/OX有良好的分离性能, 在300 ℃下, PX/OX分离因子高达42, PX的渗透性为9.57×10^-9 mol·m^-2·s^-1·Pa^-1. 采用低温臭氧脱除模板剂能够有效减小分子筛晶体热收缩产生的应力, 提高MFI型分子筛膜的分离性能. 两种方法合成的分子筛膜在低温臭氧的条件下脱除模板剂后, 都具有PX/OX分离性能, 其中变温法合成的分子筛膜PX/OX分离因子高达76, PX的渗透性为1.02×10^-8 mol·m^-2·s^-1·Pa^-1.     

二次生长法制备高分离性能的PHI分子筛膜

通过二次生长法在α-Al2O3支撑体表面合成了PHI分子筛膜,考察了晶种合成方式、二次生长合成温度及时间对形成PHI分子筛膜的影响.采用X射线衍射(XRD)、扫描电子显微镜(SEM)对合成膜进行表征.结果表明:载体表面合成出了PHI分子筛;二次生长法合成出的PHI分子筛膜连续、致密,膜厚约为20 μm.利用渗透汽化技术对甲醇、乙醇、异丙醇和叔丁醇等不同分子尺寸的醇/水体系进行分离性能的研究,同时考察原料液中水含量对所制备的PHI分子筛膜的分离性能的影响.结果表明:PHI分子筛膜对几种醇水体系都具有良好的分离效果,随着水含量的增加,水的渗透通量呈增大趋势,乙醇和甲醇的理想分离因子有所降低,异丙醇和叔丁醇的理想分离因子增大.     

具有抗生物污染活性的分子筛膜用于高效油水分离

The development of the global economy has been accompanied by frequent oil spills caused by accidental leaks and industrial manufacturing, which have seriously threatened the aquatic environment and human health. Traditional methods for the treatment of oily wastewater include centrifugation, skimming, flotation, oil-absorbing technology, etc., which are limited by low separation efficiency as well as secondary pollution during the post-processing of oil absorption materials. Recently, separation technologies utilizing the special wettabilities of filtration membranes have been developed to enrich and recycle oils from wastewater. Among these, the fabrication of superhydrophilic/underwater superhydrophobic membranes have attracted intensive research interest, which can selectively allow the passage of water through the membrane while blocking the oils. However, microorganisms are more likely to breed on these hydrophilic surfaces, eventually leading to the blockage of the membranes. In this study, ZSM-5 zeolite crystals (MFI topological structure) were coated onto the stainless-steel meshes by means of seeding and secondary hydrothermal growth. Then, 70% of the total Na⁺ ions in the zeolite channels were substituted by Ag⁺ ions via an ion exchange process. The resultant membranes (Ag@ZCMFs) were superamphiphilic in air, with both water contact angle and oil contact angle of approximately 0°. However, they became superoleophobic when immersed in water, and the underwater oil contact angle reached 151.27° ± 4.34°. In terms of special wettability, Ag@ZCMF achieved efficient separation for various oil-water mixtures with separation efficiencies above 99%. The water flux and intrusion pressure of Ag@ZCMF depended on the diameter of pinholes in the membrane, which could be modulated by altering the time of secondary hydrothermal growth. For instance, the average diameter of pinholes in Ag@ZCMF with optimum secondary growth time of 14 h (Ag@ZCMF-14) reached approximately 21 μm, giving rise to the water flux and intrusion pressure of 54720 L·m^-2·h^-1 and 4357 Pa, respectively. The anti-corrosion test and rubbing test confirmed the high chemical and mechanical stability of Ag@ZCMF-14, respectively. The separation efficiency of Ag@ZCMF-14 remained stable during ten purification-regeneration cycles, and no obvious attenuation was observed, proving the high separation stability of Ag@ZCMF-14. Furthermore, the loaded Ag⁺ ions afforded the membrane excellent anti-biofouling activity, which could effectively inhibit the growth of both alga and bacteria in the operating environment, thus preventing membrane blockage during the oil-water separation process. In particular, the bacteriostatic rate of Ag@ZCMF-14 to Escherichia coli reached to 99.6%. These results demonstrate that Ag@ZCMFs with anti-biofouling activity has promising potential future applications in the removal of oil slicks from oily wastewater.     

两步变温法微米晶种诱导合成高性能的T型分子筛膜

在预涂自制微米晶种的多孔管状莫来石支撑体表面上,采用两步变温法诱导合成T型分子筛膜。在溶胶配比nSiO2∶nAl2O3∶nNa2O∶nK2O∶nH2O=1∶0.05∶0.3∶0.1∶30合成条件下,通过变温晶化过程成功制备出高性能的T型分子筛膜。XRD和SEM结果表明,该法可在支撑体表面上较快地形成一层连续致密的纯相T型分子筛膜层,较大缩短了膜合成时间和提高了膜致密性。在优化条件下所合成的膜具有优异的渗透汽化性能,且膜制备的重复性良好。75℃时,在水/异丙醇(10/90,w/w)混合物体系中膜的渗透通量和分离因子分别高达4.25 kg.m-2.h-1,7600;在水/乙醇(10/90,w/w)混合物体系中膜的渗透通量和分离因子分别为2.87 kg.m-2.h-1,1 900。     

Synthesis Optimization of SSZ-13 Zeolite Membranes by Dual Templates for N2/NO2 Separation

High-silica SSZ-13 zeolite membranes are promising in industrial separations of light gases and continuous membranes are highly demanded for better separation performances. Herein, pure-phase, continuous and thin SSZ-13 zeolite membranes were synthesized using dual templates of N,N,N-trimethtyl-1-adamantammonium hydroxide(TMAdaOH) and tetraethylammonium hydroxide(TEAOH). Systematical investigations of TMAdaOH/TEAOH ratios and their concentrations show that TMAdaOH acts as the main structure-directing agent in the formation of the SSZ-13 zeolite. TMAdaOH cooperatively plays with TEAOH in promoting the SSZ-13 crystal intergrowth to form a continuous polycrystalline membrane. Additionally, appropriate introduction of TEAOH is able to adjust the membrane thickness to the crystal-comparable size of ca. 2.0 μm. The SSZ-13 membranes are further applied for N₂/NO₂separation, which is firstly reported on zeolite membranes. The gas permeation results show that the SSZ-13 membrane synthesized by the dual-template approach exhibits selective separation of N₂ over NO₂ with N₂/NO₂ separation factor of 7.6 and N₂ permeance of 1.66×10^-8 mol·m^-2·s^-1·Pa^-1.     

高硅MFI分子筛膜的合成与低温脱除膜内有机模板剂

采用旋涂法在粗糙的α-Al₂O₃载体片上制备出较完备的分子筛晶种层;以四丙基氢氧化铵(TPAOH)为有机模板剂,通过调控合成液的H₂O/Si摩尔比,实现了对分子筛晶体面内优先生长的调控;经过三次水热合成得到致密交联的h0h-轴取向高硅MFI分子筛膜,膜厚约为8 μm(包括~5 μm致密层和~3 μm过渡层)。采用先低温加氢裂解后低温空气氧化的两步法脱除工艺,有效脱除了分子筛膜内的有机模板剂。相比于传统高温煅烧法,该法可以避免分子筛膜因脱除模板剂而形成的较大晶间缺陷。因而采用低温两步法脱除模板剂的分子筛膜片在30 ℃时具有较好的CO₂分离效果,其CO₂/N₂分离因子达到5.2, CO₂渗透通量高达5.8 × 10^-7mol·m^-2·s^-11·Pa^-1。     

微波加热合成含有极少量非分子筛缺陷孔的LTA型分子筛膜

 以改进的原位合成路线,于管状氧化铝载体上合成了高性能的LTA型分子筛膜. 考察了常规加热和微波加热对合成的影响. 对于95%的异丙醇原料液,常规加热合成和微波加热合成的分子筛膜表现出了相似的优良性能. 但是,当原料液中的水含量低于2.0%时,常规加热合成的分子筛膜不再具有有效的脱水性能,这是由于其膜层中有相当数量的纳米级缺陷孔存在. 采用微波加热在很大程度上消除了合成过程中非分子筛缺陷孔的生成.     

高性能AlPO4-14分子筛膜的制备及气体分离性能

制备了高性能的AlPO₄-14分子筛膜. 首先通过控制反应溶胶中水和模板剂的含量制备了形貌均一的AlPO₄-14分子筛, 分子筛的尺寸为15~18 mm; 然后采用晶种法即在反应凝胶中加入分子筛作为晶种进一步调控分子筛的大小, 使得AlPO₄-14分子筛的尺寸从15~18 mm减小到2~3 mm, 得到形貌均一的纯相片状晶体, 同时有效缩短了制备时间; 最后以多孔管状莫来石为支撑体, 采用二次生长法制备AlPO₄-14分子筛膜. 考察了2种不同大小的晶种对膜形貌和性能的影响, 发现以大尺寸的分子筛(15~18 mm)作为晶种制备的分子筛膜的分离层存在较多缺陷, 而采用小尺寸的晶种(2~3 mm)制备的膜层较均一致密. AlPO₄-14分子筛膜经高温脱除模板剂后仍然保持着纯相的AlPO₄-14晶型, 表明二次生长法促进了AlPO₄-14晶体在膜层中的生长且使其具有更高的结晶度和热稳定性. 在25 ℃, 100 kPa下, AlPO₄-14分子筛膜对H₂/CH₄, CO₂/CH₄和H₂/CF₄的理想分离因子分别为28, 40和1047, 且H₂和CO₂的渗透速率分别为6.3×10 ^-7和9×10 ^-7 mol·(m ²·s·Pa) ^-1; 对等摩尔CO₂/CH₄混合气体的分离因子为81.5, 且CO₂的渗透速率为8.8×10 ^-7 mol·(m ²·s·Pa) ^-1.     

Facile preparation of compact LTA molecular sieve membranes on polyethyleneimine modified substrates

A facile preparation strategy was proposed for preparation of compact zeolite LTA membranes on polyethyleneimine(PEI) modified substrates without seeding.Through the functionalization of substrates by using PEI,compact LTA membranes can be formed on various kinds of substrates.A well-intergrown and phase-pure LTA membrane with a thickness of about 3.0 μm is successfully prepared on the a-Al_2 O_3 disk after crystallization for 24 h at 60℃.Besides LTA membrane,wellintergrown zeolite FAU membranes can also be formed on PEI-modified a-Al_2 O_3 substrates,suggesting the universality of this strategy.The zeolite LTA membranes synthesized on PEI-modified a-Al_2 O_3 tubes we re evaluated fo r the separation of alcohols/water mixture through pervaporation.The as-synthesized zeolite LTA membranes display high pervaporation performances.For the separation of 10 wt% isopropanol/water solution at 90℃,a high separation factor of44991 and a water flux of 1.73 kg m ~2 h ~1 are achieved.     

具有水下超疏油性能的MXene高效油水分离膜

基于二维材料MXene(Ti₃C₂T_x)的化学组成和纳米片状结构, 在不锈钢网上制备了具有MXene微纳结构表面的新型亲水和水下超疏油分离膜. 对于不同类型的油-水混合物, 该膜材料可实现重力驱动的高效油水分离, 收集的水中残油量小于4 mg/L, 具有高分离效率(>99.99%), 水通量高达57.52 L·m^-2·s^-1. 此外, 经高温处理和多种有机溶剂浸泡后MXene膜仍具有高效的油水分离性能, 并表现出优异的稳定性和循环性.     

二次生长法NaA沸石分子筛膜的合成与表征——推荐一个研究型综合实验

介绍一个研究型综合实验——二次生长法NaA沸石分子筛膜的合成与表征。实验预先利用热浸渍法在α-Al_2O_3多孔载体管外表面引入NaA沸石分子筛晶种,再通过二次生长法合成NaA沸石分子筛膜。用扫描电子显微镜和X射线衍射仪表征载体管和NaA沸石分子筛及膜的形貌和结构,并利用渗透蒸发乙醇脱水膜分离装置测试膜的分离性能。通过本实验使学生了解膜分离技术这一科学前沿领域,激发学生对科学研究的兴趣,培养学生的科研探究能力。本实验涵盖合成、表征及性能测试,知识要点多、学科覆盖面广,有利于提升学生的实践操作能力、创新意识和综合运用知识的能力。     

Effects of synthesis parameters on zeolite membrane formation and performance by microwave technique

Recently, zeolite membranes on porous supports have been extensively studied in the ethanol–water separation process for further use for gasohol production. This work focuses on a NaA membrane synthesized on an α‐Al₂O₃ support via microwave hydrothermal treatment. Synthesis temperature and time, type of substrate, seed amount and seeding time for the layer growth of the membrane are considered. The formation of as‐synthesized membranes is discussed according to observations by SEM and XRD. In addition, a preliminary study of the performance of the synthesized NaA zeolite membrane was conducted using the pervaporation technique. It was found that, for the synthesized continuous NaA membranes prepared using a 0.5 µm NaA crystal seed concentration of 3 g/l via vacuum seeding, the optimum conditions were 363 K synthesis temperature for 15–20 min via microwave heating. The flux and the separation factor obtained were 1.6 kg/m² h and 1760.5, respectively, for the substrate without an intermediate layer. Interestingly, the substrate with an intermediate layer showed better flux and separation factor at 1.7 kg/m² h and 6532.7, respectively. Copyright © 2007 John Wiley & Sons, Ltd.     

ZSM-5沸石膜的吸附表征

The framework and thickness of synthesized ZSM-5 membranes were characterized using static and dynamic adsorption methods. It is shown that the adsorptive properties of the membranes are the same as ZSM-5 zeolite, the average thickness of the membranes was 13 μm calculated from the adsorptive ability, which matched very well with the result measured by scanning electron micrograph. The results also shown that zeolite membranes have greated adsorptive ability than zeolite powders. The high Si/Al rate zeolite membranes have selective ability on ethanol/water, and this interpreted the separation of ethanol-water mixtures with the membranes.     

Zeolite Membranes: From the Laboratory Scale to Technical Applications

Current trends and novel concepts in R&D of zeolite membranes like the seeding supported crystallization and the preparation of Al-containing zeolite membranes are discussed. The influences of adsorption and diffusion on the permeation properties of zeolite membranes are considered. Dehydration of ethanol by steam permeation and pervaporation as the first zeolite membrane based industrial separation is presented. Membrane supported dehydrogenation and esterification are discussed as possible applications of a catalytic membrane reactors. In memoriam Wolfgang Schirmer.     

Electrolysis of sodium chloride using composite poly(styrene-co-divinylbenzene) cation exchange membranes

Composite cation exchange membranes are prepared from cross-linked styrene-divinylbenzene copolymers for the electrolysis of sodium chloride to produce sodium hydroxide and chlorine by selective removal of sodium ions. It is prepared from a syrup of the polymer using dual initiating system and is modified with chloroacetic acid to introduce acid functional groups (COO⁻) on its surface. The effect of the modification is confirmed by FTIR, SEM, contact angle, water content, and ion exchange capacity measurements. The performance of the membrane has been evaluated in terms of current efficiency and power consumption and the effect of current density, salt concentration and flow rate on efficiency has been studied. Our membrane has an ion exchange capacity of 0.833 meq./g which is close to that of the commercially available Nafion-117 membrane having an ion exchange capacity 0.9 meq./g. The Nafion-117 used for electrodialysis of sodium sulfate has a current efficiency of around 90% and specific energy consumption of 0.1 kW/mol at 2N concentration of the salt at 1000 A/m². Our membrane used for electrodialysis of sodium chloride has a current efficiency of 93% and a power consumption of around 0.3122 kW/mol at the same concentration of salt and at a current density of 254 A/m². The two-dimensional space-charge model in cylindrical coordinates has been solved semi-analytically to obtain the effective wall potential and pore size of the membrane which are difficult to measure directly. The experimentally obtained solute flux and current density have been fitted to the model and optimum values of effective wall potential and pore diameter have been determined to be 98.5 mV and 0.8 nm, respectively.     

高性能Silicalite-1分子筛膜的合成

 本文首次利用自制的多孔二氧化硅载体, 通过二次原位水热合成出具有较高分离性能的Silicalite-1分子筛膜, 对其进行了SEM表征, 并利用渗透气化装置对乙醇-水的分离能力进行了评价, 同时还研究了乙醇-水原料液温度对Silicalite-1分子筛膜分离性能的影响.     

Superhydrophobized Polyacrylonitrile/Hierarchicall-FeOOH Nanofibrous Membrane for High-salinity Water Treatment in Membrane Distillation

Water flux and hydrophobic durability play important roles in membrane distillation(MD) applications. Compared with the method of adsorbing nanoparticles by electrostatic adsorption, the surface roughness constructed by chemical bonding is more conducive to the performance of membrane. This paper reports a facile approach to fabricating superhydrophobic fluoroalkyl silane/polydimethylsiloxane@FeOOH@stabilized polyacrylonitrile(FAS/PDMS@FeOOH@SPAN) nanofibrous membrane (NFM) with outstanding hierarchical structures, aiming to achieve efficient and stable performance in MD. Electrospun polyacrylonitrile(PAN) membrane after peroxidation was chosen as the base membrane, followed by in-situ synthesis of iron oxyhydroxide and liquid-phase silanization. We tested the characteristics of FAS/PDMS@FeOOH@SPAN NFM in each preparation stage and its performance in direct contact membrane distillation(DCMD). The chemical bond between iron oxyhydroxide and the membrane is stronger, making the rough structure steady and dense. The FAS/PDMS@FeOOH@SPAN NFM exhibited a water contact angle of 155.4° and excellent hydrophobicity towards different pollutants. Besides, it showed satisfied properties with a water flux of 24.7 L·m^-2·h^-1, a high salts rejection of ca. 100% and an extended-term stability in DCMD using hypersaline water(10%, mass ratio). It is believed that this novel study proposes a universal and efficient method to fabricate a superhydrophobic surface and has great potential for high-salinity wastewater treatment in MD.