中空纤维封闭液膜技术的传质强化研究

以３０％ＴＢＰ（灶油）为萃取剂，ＮａＯＨ水溶液为反萃剂，对聚砜中空纤维封闭液膜萃取苯酚的传质性能进行了实验研究，并在膜器的壳程鼓入空气以期强化过程传质性能，研究结果表明，在中空封闭液膜萃取过程中总传质系数与料液相流速的１／３次方成正比，因为反应速度很快反萃相的传质阻力可以忽略，在鼓入空气的情况下，总传质系数较无气泡鼓入时明显增大，总传质系数仍与料液相流速的１／３次方成正比，而与反萃相的流速基本无关     

膜萃取去除水中氯仿的研究

采用煤油－氯仿－水为实验体系,在两种不同型号的的聚丙烯中空纤维膜器中进行了连续逆流膜萃取过程的研究．计算了基于水相的总传质系数Ｋｗ,分析了实测值与计算值之间的偏差．实验结果表明,传质由水相边界层控制,壳程的非理想流动是造成偏差的主要原因．通过计算传质单元高度ｈＨＴＵ及测定萃取前后氯仿水溶液的ＣＯＤ值,证明了中空纤维膜萃取去除水中氯仿的高效性     

膜气液接触过程的研究进展

在膜气液接触过程中,气液流速可操作范围宽,结构紧凑,易于放大,不存在液泛、沟流和雾沫夹带等问题,已成为膜科学与技术研究的热点之一.分别介绍了膜气液接触器的结构,气液传质过程中气膜传质阻力、膜阻力和液膜传质阻力的估算以及影响这些阻力的主要因素,膜气液接触过程在气体分离、无泡曝气、饱和烃/不饱和烃分离、废气中VOCs脱除和纳米粒子制备等方面的应用,并对膜气液接触过程的发展方向进行了展望.     

单束中空纤维膜器中膜萃取研究

本文以50%TBP—苯酚—水和50%TBP—醋酸—水为实验体系,在单束中空纤维膜器中研究了膜萃取过程的传质特性,并集中探讨了膜材料浸润性能对传质速率的影响。研究结果表明,疏水膜器适用于相平衡分配系数m>>1的体系,亲水膜器则适用于m<<1的体系。本文提出的单束中空纤维膜器的实验方法用于膜萃取研究简单易行,尤其适用于开发新的膜材料。     

中空纤维膜萃取器的传质性能及强化

综述了中空纤维膜萃取器的传质性能及强化的研究现状。详细论述了包括壳程,膜内和管程的传质特性以及膜萃取的传质强化方法。     

脱除CO2的膜吸收过程研究

研究了用中空纤维膜组件脱除CO2的吸收过程,制备了一系列不同装填率的中空纤维膜组件．用这些膜组件进行实验,以不同浓度的单乙醇胺（MEA）溶液为吸收剂,研究了气液两相的流量和浓度、组件的装填率、吸收剂的循环使用等因素对CO2膜吸收过程的影响．实验结果表明：气、液相流量的增大和液相MEA浓度的增加都可使CO2的传质通量增大;气相CO2浓度的增加会使总传质系数减小;在组件进口气液流量和浓度相同的条件下,组件装填率（0．5％～21％）的变大有利于CO2的脱除;随着吸收液循环次数的增加,CO2的传质通量和其脱除率都会降低．     

中空纤维封闭液膜用于乳酸分离

利用中空纤维封闭液膜技术对乳酸的分离进行了研究，采用三烷基胺（７３０１）＋正辛醇＋煤油混合溶剂为萃取剂，以水作为反萃剂，在聚砜中空纤维膜器中进行实验。研究结果表明，在中空纤维封闭液膜技术分离乳酸中，总传质阻力与料液相流速和反萃相流速的１／３次方均呈反比关系。实验研究了鼓泡技术对强化质的影响，在中空纤维膜器壳程中鼓入空气有利于提高传质系数。实验中还讨论了反萃液温度对过程的影响，传质阻力随着操作温度的     

液膜法萃取青霉素的研究

介绍了乳状液膜法萃取模拟发酵液中青素的研究工作，考究了混合槽中液膜组成、试剂比、油内比、乳水比及外水相ＰＨ变化对传质过程的影响，找出了一个较为适宜的液膜组成及室浊下适宜操作的萃取工艺条件。     

中空纤维膜萃取器的分离效率

本文以不同体积浓度的TBP(煤油)—苯酚—水为实验体糸,研究了中空纤维膜萃取器的分离效率。结果表明,由于体系的萃取相平衡常数m值很高,过程的膜阻得到有效的控制,其分离效率相当可观。本文还计算比较了中空纤维膜萃取器和填料萃取柱的工况。中空纤维膜萃取器提供了巨大的传质比表面积,其HTU值很低,一般与填料萃取柱的研究中报道的最低限值相当。     

利用螺旋管技术提高中空纤维膜传质性能

在对中空纤维膜萃取以及螺旋管技术进行充分调研的基础,选择水－苯酚－30％（质量分数）TBP煤油为实验体系,传质方向为水相到有机相,在内径为1.1mm的直管中空纤维膜和螺旋状中空纤维膜中,研究了管内外流速以及螺旋特征等因素对传质系数的影响,实验结果表明,用螺旋管中空纤维膜可以有效地提高空纤维膜的传质特性,在螺旋内径为6mm,螺距为2cm的时候,总传质系数可以是相同条件下直管传质系数的1－2倍。     

Separation and recovery of critical metal ions using ionic liquids

Separation and purification of critical metal ions such as rare-earth elements (REEs), scandium and niobium from their minerals is difficult and often determines if extraction is economically and environmentally feasible. Solvent extraction is a commonly used metal-ion separation process, usually favored because of its simplicity, speed and wide scope, which is why it is often employed for separating trace metals from their minerals. However, the types of solvents widely used for the recovery of metal ions have adverse environmental impact. Alternatives to solvent extraction have been explored and advances in separation technologies have shown commercial establishment of liquid membranes as an alternative to conventional solvent extraction for the recovery of metals and other valuable materials. Liquid membrane transport incorporates solvent extraction and membrane separation in one continuously operating system. Both methods conventionally use solvents that are harmful to the environment, however, the introduction of ionic liquids (ILs) over the last decade is set to minimize the environmental impact of both solvent extraction and liquid membrane separation processes. ILs are a family of organic molten salts with low or negligible vapour pressure which may be formed below 100 ℃. Such liquids are also highly thermally stable and less toxic. Their ionic structure makes them thermodynamically favorable solvents for the extraction of metallic ions. The main aim of this article is to review the current achievements in the separation of REE, scandium, niobium and vanadium from their minerals, using ILs in either solvent extraction or liquid membrane processes. The mechanism of separation using ILs is discussed and the engineering constraints to their application are identified.     

Liquid membrane operations in a microfluidic device for selective separation of metal ions

A three-phase flow, water/n-heptane/water, was constructed in a microchannel (100-microm width, 25-microm depth) on a glass microchip (3 cm x 7 cm) and was used as a liquid membrane for separation of metal ions. Surface modification of the microchannel by octadecylsilane groups induced spontaneous phase separation of the three-phase flow in the microfluidic device, which allows control of interfacial contact time and off-chip analysis using conventional analytical apparatus. Prior to the selective transport of a metal ion through the liquid membrane in the microchannel, the forward and backward extraction of yttrium and zinc ions was investigated in a two-phase flow on a microfluidic device using 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (commercial name, PC-88A) as an extractant. The extraction conditions (contact time of the two phases, pH, extractant concentration) in the microfluidic device were examined. These investigations demonstrated that the conventional methodology for solvent extraction of metal ions is applicable to solvent extraction in a microchannel. Finally, we employed the three-phase flow in the microchannel as a liquid membrane and observed the selective transport of Y ion through the liquid membrane. In the present study, we succeeded, for the first time, in the selective separation of a targeted metal ion from an aqueous feed solution to a receiving phase within a few seconds by employing a liquid membrane formed in a microfluidic device.     

Simultaneous extraction and concentration by on-line hollow fiber membrane extraction

In the determination of trace-level pollutants in water, a concentration step is usually needed between extraction and analysis. In this paper, simultaneous extraction and concentration during on-line analysis using hollow fiber membranes is reported. Solvent loss across the membrane resulted in simultaneous concentration during extraction and had pronounced influence on enrichment factor and extraction efficiency. This phenomenon is an important consideration for analytical methods employing solvent extraction across a membrane, because it is possible to eliminate the concentration step. Continuous on-line monitoring of semivolatile compounds was achieved using this approach, and the effects of process variables on enrichment and extraction efficiency were studied. It was found that enrichment increased with solvent loss, even when the extraction efficiency decreased.     

Membrane-assisted solvent extraction of triazines, organochlorine, and organophosphorus compounds in complex samples combined with large-volume injection-gas chromatography/mass spectrometric detection

The performance of the fully automated membrane-assisted solvent extraction was investigated for 47 environmental contaminants (among them 30 organochlorine compounds, 9 organophosphorus compounds, and 7 triazines). The extraction took place in a 20-mL headspace vial filled with the aqueous sample and containing a polypropylene membrane bag with 1 mL of cyclohexane as extractant. This device was handled by a multipurpose sampler, which enabled the sample to be mixed at a defined temperature with subsequent large-volume injection of the organic extract taken out of the membrane bag. After optimization of extraction parameters, the method was validated for the three compound classes, triazines and organochlorine and organophosphorus compounds, using spiked distilled water. Then, the extraction yield of these analytes from several complex samples such as a natural and a synthetic wastewater, a bacterial culture, and orange juice was determined and compared to a conventional liquid-liquid extraction. Furthermore, the possibility of reducing matrix interference by adding salt, methanol, or detergent during membrane-assisted solvent extraction was investigated.     

Solvent bar microextraction

In this work, a new and simple microextraction method termed solvent bar microextraction (SBME) was developed. In this method, the organic extractant solvent (1-octanol) was confined within a short length of a hollow fiber membrane (sealed at both ends) that was placed in a stirred aqueous sample solution. Tumbling of the extraction device within the sample solution facilitated extraction. Pentachlorobenzene (PCB) and hexachlorobenzene (HCB) were used as model compounds to investigate the extraction performance. Analysis was carried out by gas chromatography/electron capture detection. This new method provided very high enrichment (approximately 110-fold for PCB and approximately 70-fold for HCB) in 10 min and good reproducibility (<4%, n = 6). Since the hollow fiber membrane was sealed, it could be used for extraction from "dirty" samples, such soil slurries. This novel microextraction method was compared with single-drop microextraction and static hollow fiber membrane microextraction in which the extractant solvent was also held within a hollow fiber but with the latter fixed to a syringe needle (i.e., there was no tumbling effect). Comparison between SBME and conventional solid-phase microextraction in a soil slurry sample was also investigated.     

稳定性膜萃取锂离子的研究

盐湖蕴藏的锂资源中较高的镬锂比增加了锂提取的难度,本文报道膜萃取技术在锂离子提取的方面的工作进展.耐有机萃取剂的膜材料是膜萃取技术的关键.采用亲水/疏水复合材料,避免了有机萃取剂流失和解决材料在有机相中的稳定性问题.结果表明,采用TBP萃取剂可以实现锂镁有效分离,为下一步工作奠定了基础.     

溶液中镓的提取与分离研究进展

从钢铁、有色金属、煤化工及磷化工等行业中的含镓物料中回收镓,需面临从含有多种金属离子的溶液中分离镓的问题。综述了含镓溶液中提取和分离镓的研究现状,分析和讨论了溶剂萃取、液膜萃取、萃淋树脂萃取等工艺的关键影响因素,并展望了研究趋势。溶剂萃取、液膜萃取及萃淋树脂萃取工艺皆能有效提取和分离溶液中的镓,其中协同萃取、液膜萃取及萃淋树脂萃取的选择性和萃取效率高,而且流程短、环境友好,应用前景好,是今后研究的发展方向。     

Porocritical fluid extraction from liquids using near-critical fluids

In this article, Californian-based scientist Marc Sims describes a process of liquid/liquid extraction using supercritical or near critical CO₂ as the extractant solvent in a membrane separation process. Using hollow fibre or spiral wound membranes, Sims found that the transport of solutes through a membrane in a near critical fluid resulted in highly efficient separations.     

Dialysis of persistent organic pollutants and polycyclic aromatic hydrocarbons from semipermeable membranes. A procedure using an accelerated solvent extraction device

Accelerated solvent extraction (ASE) is one of the most recent solid-phase extraction methods and has caught on all over the world in numerous laboratories. Until now it was not known that this device is also very suitable for performing dialysis. In this study, development of a rapid dialysis procedure (RDP) was described that is based on the dialysis of persistent organic xenobiotics from triolein-containing semipermeable membrane devices (SPMDs) using ASE. All the operating parameters were optimized within the framework of usage. The RDP procedure was compared with the conventional dialytic recovery of target analytes under atmospheric pressure using spiked analytes and real field samples of SPMDs exposed to urban air. The main advantages of the RDP in comparison to the conventional dialysis are the speed, with up to 70 times faster taking only 40 min, and the considerable reduction in solvent consumption (by two-thirds) when SPMDs with standard configuration are used. Moreover, the RDP is also suitable as an analytical cleanup procedure for the same analytes from various types of lipid samples and other difficult matrixes using semipermeable membranes.     

双极性膜电渗析法处理乳酸三甲胺反萃液可行性研究

采用络合萃取法提取发酵液中的乳酸过程中,在利用三甲胺进行溶剂再生时,无法对生成的乳酸三甲胺进行加热分解．采用双极性膜电渗析法处理乳酸三甲胺反萃液,使溶剂再生,并获得乳酸产品．结果表明,用双极性膜电渗析处理乳酸三甲胺反萃液,可以得到纯乳酸,回收率可以达到90％以上．