Diluents And Modifiers:

In the previous section, we have seen that different categories of extractants are available and the range is very broad. The different extractants have their own advantages and limitations. One particular point which should be kept in mind is that the majority of extractants are either solids or their viscosities are too much high for their direct use in the solvent extraction. It is, therefore, a common practice to dissolve them in a suitable solvent which is known as diluent. Thus, the diluent refers to the organic liquid in which the extractant is dissolved to form the solvent. In majority of cases, the diluent comprises the major portion of the solvent. During the solvent extraction, sometimes the formation of a third phase takes place and to avoid this, a modifier may have to be added to the solvent system. In view of the importance of diluents and modifiers to make an extractant system workable, it may be essential to discuss their characteristics. Proper selection of diluent and modifier can be as important as selecting the extractant because of their physical and chemical effects on the process. Also, they may influence the economics of the process to a great extent.