聚酰亚胺渗透汽化膜的结构对其吸附特性的影响

以3种二酐和3种二胺为单体,合成了9种不同结构的聚酰亚胺(PI)均质膜;在303.15 K下分别测量了水蒸气小分子在PI膜中的动态吸收曲线;并通过计算反常扩散指数(dW),讨论了聚酰亚胺膜材料的吸附性能与结构的关系.     

聚酰亚胺膜在不同醇／水体系中的溶胀特性

用3,3',4,4'-二苯醚四羧酸二酐(ODPA)和4,4'-二氨基二苯甲烷(MDA)为单体合成聚酰亚胺(PI)膜,测定了PI膜在单组分溶剂(甲醇、乙醇、异丙醇、叔丁醇、水)和质量分数88%双组分溶液(甲醇/水、乙醇/水、异丙醇/水、叔丁醇/水)中的溶胀特性,并考察了不同醇浓度对PI膜溶胀特性的影响.实验结果表明,PI膜在不同醇/水溶液体系中的溶胀度顺序为甲醇>乙醇>异丙醇>叔丁醇.PI膜的溶胀度(SR)和溶解选择因子(as)均随着溶液中醇的质量分数增加呈现先增加后减小的趋势,并且膜从优先溶醇转化为优先溶水.     

聚酰亚胺渗透汽化膜的研究(Ⅲ)水蒸气小分子在PI膜中的传质行为

以2种二酐、2种二胺为单体,制备了4种不同结构的聚酰亚胺(PI)均质膜;用建立的动态吸附／脱附实验装置测定水蒸气在PI膜中的吸附／脱附行为;考察了不同结构的PI膜对水蒸气吸附／脱附的影响;计算了反常扩散指数;研究了温度对水蒸气在聚酰亚胺膜(PI)中扩散系数的影响．分析了扩散系数与温度和聚合物重复单元的摩尔自由体积之间的关系．研究结果表明:水蒸气小分子在PI膜中的扩散系数随着温度增加而增加,随着聚合物重复单元摩尔自由体积的增加,扩散系数也呈上升的趋势．     

渗透物小分子在致密高聚物膜内传递行为的研究(Ⅱ)动态吸附行为

推导出了整个扩散区的扩散方程和动态吸附初期的吸附方程 ,实验研究并分析了CH2 Cl2 、CH3OH、CH3CH2 OH和H2 O 4种渗透物小分子在不同厚度的聚酰亚胺高聚物膜内的动态吸附行为 ,并计算出了反常扩散指数dw.     

聚酰亚胺渗透汽化膜的研究(Ⅰ)膜的制备和结构对动态吸附特性的影响

以2种二酐，3种二胺为单体，两步法制备了6种不同结构的聚酰亚胺均质膜，通过红外光谱和元素分析证实了其重复单元的分子结构，测定了这几种膜的物理性质和对水蒸气的动态吸附性能，并计算出其反常扩散指数dw。实验表明，随着聚合物二胺单元分子结构的变化，按MDA、ODA、PDA的顺序，密度逐渐变大，链间距逐渐减小，链堆砌变得紧密，水蒸气在膜中的吸附和扩散也变慢，并出现从正常扩散到反常扩散的过渡现象。     

金属有机骨架/聚酰亚胺复合膜材料的制备及脱硫特性

采用相分离方法制备了新型金属有机骨架(MOFs)/聚酰亚胺(PI)复合膜,考察了膜的形态结构、吸附通道与吸附行为的关系。结果表明:功能膜具有发达的孔结构,功能颗粒镶嵌于基膜的三维网络通道中;膜的断面形态结构随凝固浴的不同而有显著区别,以水、乙醇、异丙醇的顺序,断面形态从指状孔结构逐渐向海绵状孔过渡;膜的吸附行为与膜三维通道结构、金属有机骨架的独特网兜结构及络合吸附作用密切相关;膜具有良好的热稳定性,膜吸附容量可达18mg/g。该复合膜在有机物吸附分离、膜分离等领域中具有潜在的用途。     

凝胶介质对聚酰亚胺膜凝胶速率胶膜断而结构的影响

以一种可溶性的新型聚酰亚胺ODPA-BAPP为膜材料,N-甲基吡咯烷酮(NMP)为溶剂,采用浸入凝胶相转化法制备非对称膜.分别以水乙醇正丙醇异丙醇正丁醇以及正戊醇作为凝胶介质,用凝胶动力学测定装置和相分离动力学测定仪分别对其成膜过程中的凝胶速率和相分离时间进行测定.研究结果表明:(1)凝胶介质对凝胶速率大小影响的排序依次为:水>乙醇>正丙醇>异丙醇>正丁醇>正戊醇;(2)瞬时相分离易生成指状结构的膜,延时相分离易生成海绵状结构的膜,与相关文献报道一致.     

不同结构聚酰亚胺膜在乙醇/水体系中的溶胀特性

用5种二胺和4种二酐合成了2个系列8种不同结构的聚酰亚胺(PI)均质膜.测定了不同结构PI膜在质量分数为88%乙醇/水溶液中的溶胀特性,并讨论了不同二胺和二酐结构对渗透物分子在膜内的溶解特性的影响.     

水／乙醇溶液在聚乙烯醇聚电解质膜中的吸附特性

将季胺阳离子化聚乙烯醇膜材料和磷酸酯化阴离子聚乙烯醇膜材料按不同摩尔比共混制备了一系列膜,用等温吸附的方法测定了不同浓度的乙烯／水溶液在各种膜中的吸附量及吸附选择性,结果表明,与聚乙烯醇膜相比,水／乙醇在各种聚电解质膜中的吸附量均有不同程度的提高,当两种膜材料以接近1：1的比例共混时,各种浓度的乙醇／水溶液在该膜中的吸附量为最大,水／乙醇的吸附选择性也最大。     

新型聚酰亚胺渗透汽化膜

合成了三种新型聚酰亚胺,并制成渗透汽化膜用以分离乙醇-水、异丙醇-水混合物。结果表明,三种聚酰亚胺均具有较高的分离系数,在分子主链中含有—Si—(CH_3)_2—链节的聚酰亚胺膜,其透过速率高于、分离系数低于其它两种聚酰亚胺,并从聚合物分子结构的观点讨论了其原因。     

渗透物小分子在致密高聚物膜内传递行为的研究(Ⅰ)扩散行为的分类和描述

综述了渗透物小分子在致密高聚物膜内传递的溶解扩散模型及其不足 ,用自由体积理论和逾渗理论分析了渗透物小分子在致密高聚物膜内的扩散行为 ,提出了扩散分区图 ,并分析了渗透物分子大小、温度和致密高聚物膜性质对扩散的影响 .     

乙醇分子在PPES,PPEK,PPESK膜中动态吸收和解吸实验研究

用重量吸收法测定了298.15,303.15,308.15K下乙醇蒸气在PPEK,PPES,PPESK膜中吸收和解吸动力学数据.结果表明,随着温度的升高,乙醇在膜中的吸收/解吸行为由Non-Fick扩散向Fick扩散转变,乙醇蒸气在三种膜中吸收速度v(PPES)>v(PPESK)>v(PPEK),解吸速度v(PPEK)>v(PPESK)>v(PPES).     

Montmorillonite surface properties and sorption characteristics for heavy metal removal from aqueous solutions

Surface properties of montmorillonite (MMT) and its adsorption characteristics for heavy metals have been investigated with nickel and copper as sorbate from aqueous solutions. Employing the potentiometric and mass titration techniques in batch experimental methods, the point of zero charge (PZC) and point of zero net proton charge (PZNPC) of MMT edges at different ionic strengths present pH_PZC and pH_PZNPC to be 3.4 ± 0.2. A crossing point was observed for the proton adsorption vs. pH curves at different ionic strengths of KCl electrolyte and in investigating MMT remediation potentialities as sorbent for heavy metals polluted waters, the effects of heavy metal concentration, pH, MMT dosage, reaction time and temperature for Cu²⁺ and Ni²⁺ uptake were studied. The sorption of metal ions by MMT was pH dependent and the adsorption kinetics revealed sorption rate could be well fitted by the pseudo-second-order rate model. The data according to mass transfer and intraparticle diffusion models confirmed diffusion of solutes inside the clay particles as the rate-controlling step and more important for the adsorption rate than the external mass transfer. Adsorption isotherms showed that the uptake of Cu²⁺ and Ni²⁺ could be described by the Langmuir model and from calculations on thermodynamic parameters, the positive ΔG° values at different temperatures suggest that the sorption of both metal ions were non-spontaneous. Change in enthalpy (ΔH°) for Ni²⁺ and Cu²⁺ were 28.9 and 13.27 kJ/mol K respectively, hence an endothermic diffusion process, as ion uptake increased with increase in temperature. Values of ΔS° indicate low randomness at the solid/solution interface during the uptake of both Cu²⁺ and Ni²⁺ by MMT. Montmorillonite has a considerable potential for the removal of heavy metal cationic species from aqueous solution and wastewater.     

负载型TiO2-聚丙烯疏水复合膜的制备与表征

采用热致相分离 (TIPS)技术制备浸涂型和反应型硅藻土 -聚丙烯疏水复合膜 ,用SEM、氮吸附、红外光谱和气体渗透性能测试装置等方法表征不同的制膜方法、浸膜液浓度及冷却方式等因素对膜形态、结构和气体渗透性能的影响 .结果表明 :浸涂型聚丙烯膜球形颗粒和孔径尺寸均小于反应型聚丙烯膜 ;TiO2 -聚丙烯膜与硅藻土陶瓷支承体是通过Si—O—Ti—O—C键的价联方式形成键联型复合膜层 ;在膜内 ,气体渗透由Knudsen扩散控制 ,H2 O与N2 的分离因子分别为 2 .4 6和 2 .2 2 .     

Adsorption of food dyes acid blue 9 and food yellow 3 onto chitosan: stirring rate effect in kinetics and mechanism

Adsorption of food dyes acid blue 9 and food yellow 3 onto chitosan was studied. Stirring rate influence on kinetics and mechanism was verified. Infra-red analysis was carried out before and after adsorption in order to verify the adsorption nature. Adsorption experiments were carried out in batch systems with different stirring rates (15-400 rpm). Kinetic behavior was analyzed through the pseudo-first-order, pseudo-second-order and Elovich models. Adsorption mechanism was verified according to the film diffusion model and HSDM model. Pseudo-second-order and Elovich models were satisfactory in order to represent experimental data in all stirring rates. For both dyes, adsorption occurred by film and intraparticle diffusion, and the stirring rate increase caused a decrease in film diffusion resistance. Therefore, the film diffusivity increased the adsorption capacity and, consequently, intraparticle diffusivity increased. In all stirring rates, the rate-limiting step was film diffusion. Adsorption of acid blue 9 and food yellow 3 onto chitosan occurred by chemiosorption.     

Biocompatibility studies of polyacrylonitrile membranes modified with carboxylated polyetherimide

Poly (ether-imide) (PEI) was carboxylated and used as the hydrophilic modification agent for the preparation of polyacrylonitrile (PAN) membranes. Membranes were prepared with different blend compositions of PAN and CPEI by diffusion induced precipitation. The modified membranes were characterized by thermo gravimetric analysis (TGA), mechanical analysis, scanning electron microscopy (SEM) and contact angle measurement to understand the influence of CPEI on the properties of the membranes. The biocompatibility studies exhibited reduced plasma protein adsorption, platelet adhesion and thrombus formation on the modified membrane surface. The complete blood count (CBC) results of CPEI incorporated membranes showed stable CBC values and significant decrease in the complement activation were also observed. In addition to good cytocompatibility, monocytes cultured on these modified membranes exhibited improved functional profiles in 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay. Thus it could be concluded that PAN/CPEI membranes with excellent biocompatibility can be useful for hemodialysis.     

Recovery of process water from spent emulsions generated in copper cable factory

Treatment of waste emulsions generated in the cable factory from copper wire drawing was investigated using the integrated membrane processes: ultrafiltration (UF) and nanofiltration (NF). The application of UF tubular membranes (MWCO 100 kDa) resulted in 98% retention of oil and lubricants, whereas the degree of passage of copper ions (the major component of effluents from cable factory) was 99%. The average permeate flux amounted to 45 l/m(2) h for the transmembrane pressure of 3.5 bar during the UF pretreatment of waste emulsions. The Silt Density Index (SDI) values of UF permeates were appropriate for the application of spiral wound membranes in the NF process. The complete removal of oil and lubricants was achieved in NF process and the content of TOC was reduced by more than 90%. The rejection of copper ions in the NF process was 90% and 98% for NF270 and NF90 membranes (FILMTEC), respectively. The quality of NF permeates allows a direct reuse of treated water for the preparation of fresh emulsion.