Synthesis and Characterization of Soluble Polyimides Derived from 4,4′‐Diamino‐3,3′‐dimethyldiphenylmethane and Their Pervaporation Performances

Two kinds of soluble polyimides were synthesized from 4,4′‐diamino‐3,3′‐dimethyldiphenylmethane (DMMDA) and two dianhydrides (including BTDA, ODPA) via a two‐step method, low temperature solution polycondensation and next chemical imidization. All polyimides were readily soluble in common polar solvent, such as DMF, DMAc and NMP. The polyimides were characterized by FT‐IR, NMR, DSC, XRD and EA. The results showed that all of the polyimides revealed an amorphous nature and their inherent viscosities were 0.68–0.96 dlg^?1. The glass transition and melt temperature of these polyimides were determined by DSC and ranged from 224–283°C and 372–384°C, respectively. Thermogravimetric analysis indicated that these polyimides remained fairly stable up to a temperature around or below 400°C. Moreover, 10% mass losses were recorded at approximately 525°C in nitrogen atmosphere. They had a tensile strength in the range 89–137 MPa, and elongations breaking at around 10%. The pervaporation properties of the prepared polyimide dense membranes for ethanol/water mixtures were investigated at a different temperature and the average value of the separation factor and total permeation flux were 46–108 and 660–1380 g/m²h, respectively.     

Determination of Ammonia in Water Using Flow Injection Analysis with Automatic Pervaporation Enrichment

Abstract

An automated ammonia monitoring system has been developed by putting a pervaporation unit in an enrichment cycle used in flow injection analysis mode. In the proposed system, an enrichment cycle was equipped to enable the adjustment for the measuring range of ammonium by controlling the duration of the enrichment circulation. Therefore, the system was capable to determine ammonia in both the surface water with low ammonia concentration and the ammonia-rich wastewater with the linear dynamic range of 0.05–15 mg l^?1 and 15–50 mg l^?1, respectively. The relative standard deviations were less than 1.9% and the quantification limit is as low as 0.03 mg l^?1. The sampling frequency is 8–10 h^?1.     

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。     

PTMSP与PMP膜渗透汽化分离性能的研究比较

制备了聚三甲基硅丙炔与聚4－甲基戊烯－1均质膜，研究比较了这两种膜的分子结构与其对吡啶、丁酮和四氢呋喃三种有机液；水混合体系的渗透汽化特性同的关系，并进行了理论解释。     

Influence of modification of MWCNTs on the structure and performance of MWCNT‐Poly(MMA‐AM) hybrid membranes

Hybrid membranes containing multi‐walled carbon nanotubes (MWCNTs) were initially prepared to separate benzene/cyclohexane mixtures. Subsequently, MWCNT surfaces were chemically modified using two methods to change the surface polarity of the MWCNTs and improve the distribution thereof in Poly(methylmethacrylate) (PMMA). This change consequently enhanced the separation performance of hybrid membranes with MWCNTs. Raman spectroscopy was used to characterize the structure of the pristine MWCNTs and the modified MWCNTs. The morphology and distribution of the MWCNTs in PMMA were investigated by transmission electron microscopy. The results showed that the addition of MWCNTs clearly improved the separation performance of the hybrid membranes. Surface modification introduced polar groups onto the MWCNT surface, which significantly improved the distribution of MWCNTs in the PMMA membranes and the performance of hybrid membranes. MWCNTs with higher surface polarity also increased the amount of MWCNTs distributed homogeneously in PMMA. Aminated MWCNTs (MWCNT‐NH₂) showed the highest surface polarity. Thus, the content of MWCNT‐NH₂ well distributed in PMMA was the highest among the three types of MWCNTs. The highest separation factor for the hybrid membranes with 1.0 wt% MWCNT‐NH₂ was about seven times that of membranes containing pristine MWCNTs. Copyright © 2013 John Wiley & Sons, Ltd.     

氧化石墨烯-Ag纳米粒子/聚酰亚胺混合基质膜及其渗透汽化性能

以聚乙二醇（PEG-400）为还原剂,AgNO₃为前驱体,采用浸渍-还原法合成氧化石墨烯-Ag纳米粒子（GO-AgNP）复合物,再通过共混法制备氧化石墨烯-Ag纳米粒子/聚酰亚胺（GO-AgNP/PI）混合基质膜,用于苯/环己烷混合物的渗透汽化分离。使用透射电子显微镜、红外吸收光谱、拉曼光谱、热失重以及X射线光电子能谱等分析表征GO-AgNP复合物、GO-AgNP/PI混合基质膜的形貌和结构;探讨了Ag掺杂量对GO-AgNP复合物的结构以及GO-AgNP/PI混合基质膜的结构和渗透汽化性能的影响。结果发现,Ag⁺被还原形成AgNP的同时,GO失去了部分含氧官能团;Ag掺杂破坏了GO的结构,使其无序度增加,但改善了GO-AgNP复合物在混合基质膜中的分散性,提升了GO-AgNP/PI混合基质膜的苯/环己烷渗透汽化性能。然而过量的Ag掺杂将使GO片层上产生Ag粒子团聚,从而降低混合基质膜的渗透汽化性能。当Ag掺杂量为15%时,GO-AgNP/PI混合基质膜渗透汽化性能最佳,渗透通量为1 404 g·m^-2·h^-1,分离因子可达36.2。     

Photomodification of a poly(acrylonitrile-co-butadiene-co-styrene) containing diaryltetrazolyl groups

A new type of membrane polymer, containing a photosensitive moiety, was synthesized. The photochemically induced functionalization and crosslinking of poly [acrylonitrile-co-butadiene-co-styrene-co-2-(4-ethenyl) phenyl-5-phenyl-2H-tetrazole], ABSV, has been studied. A variety of dipolarophiles and phenolic compounds were applied to alter the polarity of the membrane surface. The functionalization and crosslinking were initiated by photoirradiation. DSC and contact angle measurements were used to characterize the modified polymer. Pervaporation experiments with a cyclohexane/benzene mixture (5 wt% benzene) were carried out, with the results showing, that the photochemical treatment significantly effects both permselectivity and flux. Solubility parameters were found to be useful to interpret the pervaporation data. In general, the selectivity towards benzene increases with the polarity of the membrane surface, i.e., with increasing polarity of the modifier. A mechanism to explain the influence of both functionalization and crosslinking on the membrane performance, is proposed. © 1994 John Wiley & Sons, Inc.     

聚苯基喹噁啉膜对有机液体混合物的渗透气化性能

研究了聚苯基喹噁啉[PPQ(B)]及聚苯基单醚喹噁啉[PPQ(E)]膜对水/乙醇、水/异丙醇、甲苯/乙醇和苯/环已烷等液体混合物体系的渗透气化特性。发现PPQ(B)、PPQ(E)膜水/乙醇及水/异丙醇混合物而言,均属水优先透过型。PPQ(E)膜在70℃下,对水/异丙醇(6.3/93.7wt%)混合液的分离系数α_(w/p)达127。实验结果还表明,PPQ(B)膜对甲苯/乙醇及苯/环已烷混合液的渗透气化分别为甲苯及苯优先透过型。对以上实验结果从理论上进行了探讨。