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1、Lession seven Solvent Extraction and Adsorption 第七课 溶剂萃取与吸收,Solvent Extraction The separation of the components of a liquid mixture by treatment with a solvent in which one or more of the desired components is preferentially soluble is known as liquid-liquid extraction. Alternative terms are liquid
2、extraction or solvent extraction. in whichpreferentially soluble是which引导的定语从句，是对solvent（溶剂）的说明,通过一种溶剂来分离液体混合物的方法叫液液萃取（？），所用的溶剂对液体混合物中目标组分具有好的溶解选择性。液液萃取也叫液相萃取和溶剂萃取。,In the operation, it is essential that the liquid-mixture feed and solvent are at least partially if not completely immiscible and, in e
3、ssence, three stages are involved: (i) Bringing the feed mixture and the solvent into intimate contact, (ii) Separation of the resulting two phases, and (iii)Removal and recovery of the solvent from each phase. it is that 是强调句型； if 引导的是条件从句。,在溶剂萃取中，液体混合物即使不能和溶剂完全混合，至少也能部分溶解，大体上来说溶剂萃取分为三个阶段： （1）使溶剂和液
4、体混合物密切接触 （2）产生的两相的分离 （3）去除和回收每相中的溶剂,Important applications of this technique include the separation of aromatics from kerosene based fuel oils to improve their burning qualities and the separation of aromatics from paraffin and naphthenic compounds to improve the temperature-viscosity characteristic
5、s of lubricating oils. It may also be used to obtain, for example, relatively pure compounds such as benzene, toluene, and xylene from catalytically produced reformates in the oil industry, in the production of anhydrous acetic acid, in the extraction of phenol from coal tar liquors, and in the puri
6、fication of penicillin. The important feature is the selective nature of the solvent, in that the separation of compounds is based on differences in solubility, rather than differences in volatility as in distillation. 两个the separation of 都是include的宾语，两个to improve都是动词不定式做目的状语。 in that in solubility是
7、that引导的定语从句，说明selective nature 。,溶剂萃取的重要应用包括：分离出煤油（燃料油）中的芳环化合物以提高燃油质量；分离出石蜡和环烷烃中的芳环化合物以提高润滑油的温度-粘度特征。也可用于获得较纯的化合物，譬如：在石油工业中接触反应的重整油中、无水醋酸的生产中、煤焦油中萃取萘的萃取物中以及青霉素的纯化过程中都可以获得苯、甲苯和二甲苯。其重要特征是溶剂的选择性，萃取分离依据的是溶解度的差异，而在精馏分离依据的是挥发能力的差异。,In the single-stage batch process, the solvent and solution are mixed toge
8、ther and then allowed to separate into the two phases: the extract containing the required solute in the added solvent and the raffinate the weaker solution with some associated solvent. With this simple arrangement mixing and separation occur in the same vessel. Equilibria in such cases are represe
9、nted conveniently on triangular diagrams, either equilateral or right-angled. Equilibria between any numbers of substances are representable in terms of activity coefficient correlations such as the UNIQUAC or NRTL.,在单级批处理工艺（过程）中，溶剂和溶液混合在一起，然后分成两相：萃取物和萃余液两相。在添加溶剂中的萃取物包含需要的溶质，萃余液中溶质含量很少。混合与分离在同一个容器中进
10、行。三角相图（等边或直角）可以方便的表示此情况下的相平衡。各物质间的平衡可以用活度系数的相互关系(UNIQUAC或 NRTL)来表示。,In theory these correlations involve only parameters that are derivable from measurements on binary mixtures, but in practice the resulting accuracy may be poor and some multicomponent equilibrium measurements also should be used to
11、 find the parameters. Finding the parameters of these equations is a complex enough operation to require the use of a computer. that引导的定语从句修饰其前的 parameters。,理论上这些相互关系涉及到的参数仅是从测量的二元混和物中推导出来的，实际上导致准确度差，一些多组分平衡测量的参数也应该使用。寻找这些多组分平衡的参数很复杂，需要借助计算机来处理。,It may be seen that successful extraction processes ar
12、e not to be judged simply by the performance of the extraction unit alone, but by assessment of the recovery achieved by the whole plant. The sections of the plant for mixing and for separation must be considered together when assessing capital cost; in addition, the cost of the organic solvents use
13、d in the metallurgical processes may also be high. thatthe whole plant是that引导主语从句，句首的IT只是形式主语。主语从句中 not to be judgedsimply by ，but by，是not but结构，表示“不是而是”的意思。 when引导的是时间状语从句。,应该知道，萃取的成功与否不是但从萃取两判断的，而要评估回收率。当核算成本时，混合及分离两部分应综合考虑，另外，在冶金工艺中有机溶剂的成本也是很高的。,Equipment for extraction must be capable of providi
14、ng intimate contact between two phases so as to affect transfer of solute between them and also of ultimately effecting a complete separation of the phases. The highest degree of separation with a minimum of solvent is attained with a series of countercurrent stages. In the operation, feed enters th
15、e first stage and final extract leaves it, and fresh solvent enters the last stage and final raffinate leaves it. so as to affect separation of the phases中，so as to affect是动词不定式做目的状语。,萃取设备应能够使两相紧密接触实现溶质在两相间转移，并最终实现两相完全分离。通过一系列的逆流阶段可达到用最少的溶剂实现最大程度的分离。萃取操作中，液相混合物进入第一阶段，最后萃取物离开它。新鲜溶剂进入最后阶段，萃余液离开它。,Abso
16、rption Though used as a physical-chemical process over a long period it is only over the last three decades that adsorption has developed to a stage where it is now a major industrial separation process. In adsorption, molecules distribute themselves between two phases, one of which is a solid whilst the other can be a fluid-liquid or gas. Unlike absorption, in which solute molecules diffuse from the bulk of a gas phase to the bulk of a liquid phase, in ad
