层层组装晶种法制备Mg-MOF-74膜及其分离性能

以2,5-二羟基对苯二甲酸和乙酸镁溶液为原料通过交替浸渍层层组装法在α-Al2O3载体表面预置晶种层,再利用二次生长法制备出连续而致密的Mg-MOF-74晶体膜。采用X射线衍射(XRD)和扫描电镜(SEM)对膜进行了表征。实验结果表明:相比于原位溶剂热合成法,通过2,5-二羟基对苯二甲酸和乙酸镁交替浸渍层层组装法可以增强Mg-MOF-74与氧化铝基体之间的附着效果,提高晶体薄膜的致密性与连续性,实验发现4次交替浸渍层层组装预置晶种可以制备出具有分子筛分性能的Mg-MOF-74晶体膜,单组分气体渗透测试表明其H2/CO2的理想选择性可以达到8.96,高于其努森扩散选择性。XRD测试表明该晶体膜的特征衍射峰与文献报告的粉末MOF-74完全一致,表明Mg-MOF-74晶粒以无取向形式生长于氧化铝载体表面。SEM表征表明Mg-MOF-74晶粒呈麦粒状微观外形,其BET比表面积可以达到1182 m2·g-1。     

层层组装晶种法制备Mg-MOF-74膜及其分离性能

以2,5-二羟基对苯二甲酸和乙酸镁溶液为原料通过交替浸渍层层组装法在a-Al₂O₃载体表面预置晶种层, 再利用二次生长法制备出连续而致密的Mg-MOF-74晶体膜。采用X射线衍射(XRD)和扫描电镜(SEM)对膜进行了表征。实验结果表明:相比于原位溶剂热合成法, 通过2, 5-二羟基对苯二甲酸和乙酸镁交替浸渍层层组装法可以增强Mg-MOF-74与氧化铝基体之间的附着效果, 提高晶体薄膜的致密性与连续性, 实验发现4次交替浸渍层层组装预置晶种可以制备出具有分子筛分性能的Mg-MOF-74晶体膜, 单组分气体渗透测试表明其H₂/CO₂的理想选择性可以达到8.96, 高于其努森扩散选择性。XRD测试表明该晶体膜的特征衍射峰与文献报告的粉末MOF-74完全一致, 表明Mg-MOF-74晶粒以无取向形式生长于氧化铝载体表面。SEM表征表明Mg-MOF-74晶粒呈麦粒状微观外形, 其BET比表面积可以达到1182 m²·g^-1。     

氧化石墨烯-陶瓷复合纳滤膜的层层自组装制备及其性能

氧化石墨烯（GO）的片层边缘含有 COOH等含氧官能团,因而带负电荷,可以在带正电荷多孔基体上通过层层自组装实现快速沉积。以由3-氨丙基三乙氧基硅烷（APTES）修饰的多孔氧化铝管式陶瓷膜为基膜,令GO和聚乙烯亚胺（PEI）以溶液形态在其表面交替沉积实现自组装,继以环氧氯丙烷（ECH）交联之,制备新型氧化石墨烯-陶瓷复合纳滤膜。最佳制备工艺是,PEI浓度5 g·L^-1、pH=9,NaCl浓度0.3 mol·L^-1,GO浓度0.6 mg·ml^-1、pH 4.5,层数2层,ECH用量6.25 ml·L^-1,50℃条件下处理70 min。层数为1～4层的自组装膜在0.6 MPa操作压力下对2 g·L^-1的MgCl₂的截留率分别为90.16%、93.71%、97.54%、92.93%,其中1层自组装膜的渗透通量为21.92 L·m^-2·h^-1。氧化石墨烯-陶瓷复合纳滤膜对4种无机盐的截留率大小为MgCl₂ >MgSO₄ > NaCl >Na₂SO₄,符合典型正电荷纳滤膜的特征。     

基于层层自组装技术的抗污染膜研究进展

膜分离技术已经广泛应用于污水处理领域,但膜污染是制约其进一步发展的主要障碍,开发抗污染膜材料实现节能降耗是目前膜法污水处理领域的研究热点之一。层层自组装作为一种膜表面改性技术,具有组装材料丰富、适用场景广泛、制备条件温和、分子水平结构可控等特点,已被应用于抗污染膜材料的研制中。本文综述了近年来基于层层自组装技术的水处理用抗污染膜的研究进展,在阐释层层自组装技术应用于膜污染控制机制的基础上,重点总结了基膜的选择和处理、抗污染组装单元的种类和复合方式、组装层数、制备方法对膜抗污染性能的影响,并对未来该技术实现膜污染控制的构筑设计和发展方向,如组装过程机制挖掘、制膜工艺优化、制膜成本降低、长期稳定性提升等方面进行了展望。     

层层自组装法制备碳纳米管薄膜研究进展

综述了近年来通过层层自组装法制备碳纳米管薄膜的一些最新研究进展,重点介绍了通过物理吸附和化学吸附两种方式来制备碳纳米管组装膜,并对如何提高碳纳米管薄膜的电化学稳定性方面进行了论述。     

层层组装氧化石墨烯基复合膜的制备及其纳滤性能研究

选用氧化石墨烯（GO）及丁二胺（BDA）在尼龙（Nylon）基底上,利用真空抽滤法多次组装制备复合膜,并将其用于有机溶剂甲醇中染料的脱除,研究了其分离性能。文中采用扫描电子显微镜（SEM）、X射线衍射仪（XRD）、接触角测量仪、X射线光电子能谱仪（XPS）等表征手段对复合膜的微观结构和组成进行了表征,并研究了GO、BDA的浓度、组装层数等因素对复合膜有机溶剂分离性能的影响,探索得出最佳分离膜的制备条件,并选用最佳条件下制备的复合膜进行有机溶剂分离性能和稳定性测试,最终得到了分离性能优异的氧化石墨烯基分离膜。     

Mg-MOF-74在Knoevenagel缩合反应中的催化性能研究

在溶剂热条件下,使用四水合乙酸镁和2,5-二羟基对苯二甲酸合成Mg-MOF-74,通过元素分析、扫描电子显微镜（SEM）、X衍射衍射光谱（XRD）、红外光谱（FT-IR）和热重（TG）表征方法,分析和确定其结构和性质。碱土金属中心和酚酸氧配体的结合,极大地增强了金属有机骨架化合物（MOFs）材料的碱性。为了探索Mg-MOF-74的催化活性,将其用于催化苯甲醛与氰基乙酸乙酯的Knoevenagel缩合反应,生成（E）-α-氰基肉桂酸乙酯。通过改变反应时间、溶剂类型、底物浓度、催化剂的量、搅拌速率和反应温度等条件来提高转化率。在较温和的条件下,反应的转化率达到94.5%,选择性大于99.5%。催化剂易于从溶液中分离出来,表现出良好非均相性。在5次循环实验之后,催化效果没有明显的降低。     

层层自组装氧化石墨烯纳滤膜的制备及表征

层层自组装法是一种新型的纳滤膜制备方法。本文采用层层自组装法制备了氧化石墨烯(GO)纳滤膜,以聚乙烯亚胺(PEI)为聚电解质,考察了不同的GO浓度对纳滤膜的结构及性能的影响,确定了最优GO浓度,并在最优的GO浓度下改变聚电解质种类,研究了其对膜的结构及性能的影响。结果表明,随着GO浓度增加,膜性能显著提升。当GO浓度为0.200mg·m L^-1时,膜对伊文思蓝的截留率达到95.4%,为最优GO浓度。在最优GO浓度下,将聚电解质PEI改为聚乙烯亚胺(HPEI),或添加交联剂乙二胺(EDA),纳滤膜的膜通量及截留率均有明显变化,其中聚电解质为HPEI的膜,水通量为135L·m^-2·h^-1·MPa^-1,对伊文思蓝的截留率近100%,为性能最优的GO复合纳滤膜。     

层层自组装制备阿维菌素微胶囊及其释药行为

以木质素磺酸钠和壳聚糖为囊材,阿维菌素为模型化合物,采用层层自组装技术制备了阿维菌素微胶囊;通过扫描电镜(SEM)表征了微胶囊的表面形貌;采用体外释药实验研究了微胶囊的释药行为。SEM显示:阿维菌素原药表面光滑,而微胶囊表面粗糙且无明显孔隙。微胶囊的体外释药实验结果表明:与阿维菌素原药相比,层层自组装制备的微胶囊具有一定缓释能力,随组装层数(0~32层)的增加,微胶囊的释药速率显著降低,释药中值时间(t50)在2.41~133.7 h内可调控。利用通用模型Mt/M∞=ktn对微胶囊体外释药实验数据进行回归处理表明,阿维菌素从层层自组装木质素磺酸钠/壳聚糖微胶囊的释放属于不规则(anomalous)释放机理。     

壳聚糖膜的制备及性能测定

以醋酸(HAc)为溶剂溶解原料壳聚糖(黏均分子量117万),流延烘干,经氢氧化钠溶液浸泡,洗涤干燥制得壳聚糖膜。详细考察了HAc浓度、原料浓度、NaOH浓度、碱液浸泡时间、增塑剂用量等因素对膜拉伸性能的影响。确定了最佳反应条件,即HAc浓度3%,原料浓度1.5%,NaOH浓度6%,碱液浸泡时间3 h,甘油加入量8%。在此条件下,壳聚糖膜的拉伸强度为88.74 MPa,断裂伸长率14.3%。     

Effects of process conditions on the formation of microporous membranes via solid-liquid thermally induced phase separation

Poly(phenylene sulfide) (PPS) membranes were formed via solid-liquid thermally induced phase separation. The effects of nucleation density () on final membrane structure were investigated. was varied by changing dissolution temperature (T _d, the temperature at which the melt-blend is formed) and polymer concentration in the initial polymer-diluent mixture.     

Preparation of silica nanospheres and porous polymer membranes with controlled morphologies via nanophase separation

ABSTRACT: We successfully synthesized two different structures, silica nanospheres and porous polymer membranes, via nanophase separation between silica sol and polymer. Silica sol, which was in-situ polymerized from tetraorthosilicate, was used as a precursor. Subsequently, it was mixed with a polymer that was used as a matrix component. It was observed that nanophase separation occurred after the mixing of polymer with silica sol and subsequent evaporation of solvents, resulting in organizing various structures, from random network silica structures to silica spheres. In particular, silica nanospheres were produced by manipulating the mixing ratio of polymer to silica sol. The size of silica beads was gradually changed from micro- to nanoscale, depending on the polymer content. At the same time, porous polymer membranes were generated by removing the silica component with hydrofluoric acid. Furthermore, porous carbon membranes were produced by using carbon source polymer through the carbonization process.     

Preparation and gas separation performance of silicone-coated polysulfone membranes

Composite membranes (CM) were prepared by coating the dense surface of different asymmetric polysulfone flat membranes (AM) with a solution of silicone rubber polymer. The surface porosity (ε) of the dense skin AM samples varied between 4 × 10^?5 and 1·5 × 10^?8, with an average mean pore size between 0·10 and 0·07 μm. Scanning electron microscopy (SEM), gas permeation experiments (H₂, N₂, CH₄, CO₂) and a simple resistance model were used for the determination of structure-permeability relationships. This study indicates that the CM prepared with polysulfone AM having ε < 3 × 10^?7, coated with a concentration of 6% silicone solution and a contact time of 1 min, has the best gas separation performance, with selectivities very close to the intrinsic polysulfone selectivities.     

Preparation of MFI type tubular membranes by steam-assisted crystallization

Zeolite MFI membranes were successfully prepared on both alumina and stainless steel tubular supports by crystallization of previously deposited silicate layers under a steam atmosphere. The resultant membranes were able to separate n/isobutane mixtures at relatively high temperatures, displaying separation selectivities of 11.3, 8.9 and 2.5 at 100, 230 and 330 °C, respectively.     

镁合金表面Mg-MOF-74/硅烷复合涂层的制备及耐蚀性

通过水热合成法制备了微米级的金属有机骨架材料Mg-MOF-74粉体,采用浸渍提拉法在AZ31B镁合金表面制备了掺杂一定量Mg-MOF-74粉体的硅烷涂层。使用扫描电镜和红外光谱仪研究了Mg-MOF-74掺杂对硅烷涂层表面形貌和组织结构的影响。结果表明：相比于单纯的硅烷涂层,Mg-MOF-74/硅烷复合涂层更加平整致密;Mg-MOF-74中的羟基与水解后的硅烷脱水缩合生成了交联密度较高的网状结构,能够有效阻挡腐蚀介质向镁基底渗透。通过极化曲线测量、电化学阻抗谱测试、浸泡试验等方法研究了Mg-MOF-74/硅烷复合涂层的耐蚀性。与纯硅烷涂层相比,Mg-MOF-74/硅烷复合涂层的腐蚀电位正移了0.121 V,腐蚀电流密度下降了一个数量级,容抗弧半径明显增大,在模拟体液中浸泡13 d后的析氢量也下降了一半,表明Mg-MOF-74/硅烷复合涂层有效提高了镁合金基底的耐蚀性。     

Effect of quenching temperature on the morphology and separation properties of polypropylene microporous tubular membranes via thermally induced phase separation

Polypropylene microporous tubular membranes were prepared by using camphene as solvent and through thermally induced phase separation at various quenching temperatures. Characterization of the resulting membrane included scanning electron microscopy, differential scanning calorimetry, and wide angle X-ray scattering. Microscopic observation showed that the membrane was composed of spherical clusters and had a leafy structure. The crystallinity increased with the quenching temperature. The crystalline structure was of smectic form. Permeation performance was also determined, including pure water permeability and retention of dextran. The results showed that at lower quenching temperatures, the structure of membrane was denser. Therefore, the permeability was lower and the retention was higher.