Industrial extractants separation factors

The component C in the separated extract from the stage contact shown in Eigure 1 may be separated from the solvent B by distillation (qv), evaporation (qv), or other means, allowing solvent B to be reused for further extraction. Alternatively, the extract can be subjected to back-extraction (stripping) with solvent A under different conditions, eg, a different temperature again, the stripped solvent B can be reused for further extraction. Solvent recovery (qv) is an important factor in the economics of industrial extraction processes. 

SOLVENT extraction (liquid-liquid extraction) is the separation and/or concentration of the components of a solution by distribution between two immiscible liquid phases. A particularly valuable feature is its power to separate mixtures into components according to their chemical type. Solvent extraction is widely used in the chemical industry. Its applications range from hydrometallurgy, e.g., reprocessing of spent nuclear fuel, to fertilizer manufacture and from petrochemicals to pharmaceutical products. Important factors in industrial extraction are the selection of an appropriate solvent and the design of equipment most suited to the process requirements. 

In Table 1, typical extracting reagents used for separation and enrichment of inorganic elements are summarized. Organophosphorus extractants are often used because of their solubility properties. Di(2-ethylhexyl) phosphoric acid is commonly applied to industrial separations because of its high extractability and high separation factors between many inorganic elements, especially for rare earth elements. Other metal ions are extracted as well as the trivalent metal ions. 

If we discount the role of (Dab/TWi) in these three expressions for AB, the separation factors are what would have been achieved in dissociation extraction from an aqueous solution to an organic solvent If, however, species A were to be reextracted back into an aqueous solution for recovery, then the liquid membrane step achieves the same goal using very little solvent and only one device (instead of an extractor and a back extractor). Such a technique is likely to be highly useful in the pharmaceutical industry. 

These are commonly used in industry for the processing of metals such as the lanthanides because the separation factors between the lanthanides are so small many extraction stages are needed. In the multistage processes, the aqueous raffinate from one extraction unit is fed to the next unit as the aqueous feed, while the organic phase is moved in the opposite direction. Hence, in this way, even if the separation between two metals in each stage is small, the overall system can have a higher decontamination factor. 

Another important application of ethyl lactate is related with the edible oil industry, taking advantage of the partial liquid-liquid miscibility that present the mixtures of ethyl lactate with different lipid type substances. This property could be exploited to develop new separation processes, similar to those mentioned in this chapter, namely the recovery of squalene from olive oil deodorized distillates and the extraction of tocopherols from olive oil. In both applications, the yield and separation factors obtained indicate good selectivity of using ethyl lactate as an extractive solvent, and demonstrate the viability of developing liquid-liquid countercurrent process using green ethyl lactate solvent in edible oil industrial applications. 

Zeolites have been used in the industrial adsorptive purification of aromahc petrochemicals since the early 1970s. The application of zeolites to aromatic adsorptive purification and extraction is a particularly suitable fit because of three major factors. The first is the inherent difficulty involved in separating certain aromatic components by distillation. Petrochemical production requires individual components be obtained in very high purity, often in excess of 99.5%. While distillation is the most popular method of separation in the petrochemical industry, it is not well suited for the final step of producing high purity single component streams from close boiling multi-component aromatics-rich mixtures. 

Supercritical fluid separation processes operate at pressures ranging from 1000 to 4000 lb/in.2, pressures that might be considered high, especially in the foods and essential oils industries. However, because of the factors just listed, supercritical fluid extraction has become eco-... 

Within the pharmaceutical industry there has always been a need for sample purity. Any compound that is a potential drug candidate can only be fully characterised and tested once it is available in a pure form. There are many purification tools available for sample clean-up, e.g. flash chromatography, solid phase extraction, etc. 1-31. However, for the more complex purification problems where the desired compound and its associated contaminants have very similar polarities, structures, etc., preparative chromatography is the method of choice due to its superior separative capabilities. Preparative chromatography can also be scaled up from lens of milligrams to tens or even hundreds of grams of compound. The other main factor in favour of this technique is its ability to be tailored for most classes of compound. 

Although Peligot observed in 1842 that uranyl nitrate is soluble in ether, it was not until materials of high purity were needed for nuclear reactors that extensive applications and developments, both industrial and analytical, were made. The literature on applications of liquid-liquid extraction (solvent extraction) is extensive for details of the various procedures the reader is referred to the original papers and to compilations. " This chapter examines separations involving distribution of a solute between two immiscible phases and chemical equilibria of significance to the distribution ratio. Batch, countercurrent, and continuous liquid-liquid extractions are described in turn, followed by consideration of the factors governing the distribution ratio and finally by some illustrative applications. 

The ability to separate a mixture of two liquid phases is critical to the successful operatiou of mauy chemical aud petrochemical processes. Besides its obvious importauce to liquid-liquid extractiou aud washing operations, liquid-liquid phase separation can be a critical factor in other operations including two-liquid-phase reaction, azeotropic distillation, and industrial wastewater treatment. Sometimes the required phase separation can be accomplished within the main process equipment, such as in using an extraction column or a batch-wise, stirred-tank reactor but in many cases a stand-alone separator is used. These include many types of gravity decanters, filter-type coalescers, coalescers filled with granular media, centrifuges, and hydrocyclones. 

---