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首页> 外文期刊>Chemical Engineering Science >Countercurrent transport of organic and water molecules through thin film composite membranes in aqueous-aqueous extractive membrane processes. Part I: experimental characterisation
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Countercurrent transport of organic and water molecules through thin film composite membranes in aqueous-aqueous extractive membrane processes. Part I: experimental characterisation

机译：在水-水萃取膜工艺中，有机分子和水分子通过薄膜复合膜逆流传输。第一部分：实验表征

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This paper presents an experimental study on organic and water mass transfer through thin film composite (TFC) membranes, made of a 2 mum thick polydimethylsiloxane (PDMS) layer coated onto a microporous support of polyethersulfone. These were used for the extraction of various organic molecules from aqueous solutions with different ionic strengths. Independent measurements of organic and water transfer rates were performed using lab-scale single- and multi-tube mass exchangers. The rate of organic transfer across TFC membranes is shown to be independent of the affinity of the organic molecules for the PDMS layer, owing to negligible mass transfer resistance in this thin layer. As a consequence, the overall mass transfer coefficient measured for aqueous-aqueous extraction of hydrophilic compounds (i.e. with low affinity for PDMS) was up to one order of magnitude larger for TFC membranes than for 350 mum thick PDMS membranes operated under the same hydrodynamic conditions. The effect of osmotic pressure on water transport through TFC membranes was assessed by liquid-liquid extraction experiments using saline solutions. Water flux increases with increasing difference in salt concentration across the membrane, due to increased activity gradient. For the range of salt concentration and PDMS layer thickness used in this work, the osmotic water flux across the membrane has only a marginal effect on the rate of organic extraction. On the other hand, the ionic strength of feed and extractive phases has a direct influence on the organic transfer, due to the dependence of transport and equilibrium properties (i.e. diffusion and partition coefficients) on salt concentration. As a result, TFC membranes exhibit an asymmetric behaviour depending on operating mode. For the same hydrodynamic conditions and ionic strength, organic flux is higher when a saline solution is on the coated side than when it is on the porous side of the membrane. This has obvious implications in the design and operation of TFC membrane processes for the extraction of organics from saline solutions. (C) 2002 Elsevier Science Ltd. All rights reserved. [References: 28]
机译：本文介绍了通过薄膜复合（TFC）膜进行有机和水质传递的实验研究，该膜由2μm厚的聚二甲基硅氧烷（PDMS）层涂覆到聚醚砜的微孔载体上制成。这些用于从具有不同离子强度的水溶液中提取各种有机分子。使用实验室规模的单管和多管质量交换器进行有机和水传输速率的独立测量。由于在该薄层中传质阻力可忽略，因此显示了跨TFC膜的有机传递速率与有机分子对PDMS层的亲和力无关。结果，与在相同流体动力学条件下运行的350微米厚的PDMS膜相比，对于亲水化合物的水-水萃取（即对PDMS具有低亲和力）测得的总传质系数高350倍。 。通过使用盐溶液的液-液萃取实验，评估了渗透压对水通过TFC膜传输的影响。由于活性梯度的增加，水通量随着跨膜盐浓度差异的增加而增加。对于这项工作中所使用的盐浓度和PDMS层厚度的范围，穿过膜的渗透水通量对有机萃取率仅具有边际影响。另一方面，由于转运和平衡性质（即扩散和分配系数）对盐浓度的依赖性，进料和萃取相的离子强度直接影响有机转移。结果，取决于操作模式，TFC膜表现出不对称行为。对于相同的流体动力学条件和离子强度，盐溶液在被覆侧时的有机通量要高于在膜的多孔侧时的有机通量。这对于从盐溶液中萃取有机物的TFC膜工艺的设计和操作具有明显的意义。 （C）2002 Elsevier ScienceLtd。保留所有权利。 [参考：28]

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