Kinetics, solvent extraction rate controlling mechanisms

The solvent extraction process of metal ions inherendy depends on the mass transfer across the interface and the reaction that occurs at the interfacial region. Therefore, the elucidation of the kinetic role of the interface was very important in order to clarify the extraction mechanism and to control the extraction rates. In 1982, Watarai and Preiser invented the high-speed stirring (HSS) method [4,5]. Figure 10.1 shows the schematic drawing of the HSS method [6]. When a two-phase system is vigorously stirred in a... 

The overall extraction process is sometimes subdivided into two general categories according to Ihe main mechanisms responsible for the dissolution stage <1) those operations that occur because of the solubility of the solute in or its miscibility with the solvenl. e.g.. oilseed extraction, and (2) extractions where the solvent must react with a constituent of the solid material in order lo prtxluce a compound soluble in the solvent, eg. tile extraction of metals front metalliferous ores. In the former case the rate of extraction is most likely to he controlled by diffusion phenomena, bui in the latter the kinetics of the reaction producing the solute may play a dominant role. 

---