Single batch extraction

Volumes VL and VG of the two immiscible liquid phases are added to the extraction vessel and a single solute distributes itself between the phases as concentrations X and Y, respectively, at a rate, Q, as shown in Fig. 3.25. 

For batch extraction, with no feed into the system, the component balances on each phase are given by  

Neglecting the effects of concentration changes on solvent density, the phase volumes will remain constant. Thus for the liquid phase with volume VL 

Kl is the mass transfer coefficient for the L phase (m/s), a is the interfacial area per unit volume (m2/m3), referred to the total liquid volume of the extractor, V is the total holdup volume of the tank, and is equal to (VL+VG). X is the equilibrium concentration, corresponding to concentration Y, given by 

The information flow diagram (Fig. 3.27) for this system shows the two component material balance relations to be linked by the equilibrium and transfer rate relationships. 

Neglecting the effects of concentration changes on solvent density, the phase 

Kl is the mass transfer coefficient for the L phase (m/s), a is the interfacial area 

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ASTM D-5233. Standard Test Method for Single Batch Extraction Method for Wastes. 

Single Batch Extractions with Chlorex, Nitrobenzene, and Acetone... 

It is desired to reduce the pyridine concentration of 5000 kg/h of an aqueous solution from 50 to 5 wt% in a single batch extraction with pure chlorobenzene. What amount of solvent is required Solve on right-triangular coordinates. Corroborate your results using the Mathcad program of Appendix G-l. 

Even with DRy equal to only 10, two successive batch extractions will transfer 99% of the material to the organic phase. If one chooses as a criterion of separation that substance A be at least 99% extracted and substance B no more than 1% extracted, then, from Equation 20.5, one must have > 100 and D Ry < 0.01 for a single (batch) extraction. 

In principle, it might be possible to effect a reasonable purification of a rare metal in solution by a single-batch extraction, if either the distribution coefficient or the solvent-to-aqueous volume ratio were high. However, a fairly high process cost would usually have been borne by the previous ore... 

Biochemical Processing. Potential ELM applications in biochemical processing (44) include the separation of aminoacids (L-phenylalanine), biochemicals (acrylic and propionic acids), and antibiotics (penicillin G) from fermentation broths. A typical ELM system for the recovery of L>phenylalanine from fermentation broths is given in Table DC (45,46). The recovery from a broth containing 12-35 g/L of L-phenylalanine can be about 80% with a single batch extraction. Hong et al. (45) obtained a recovery of about 99% with four serial batch extractions in simulating their proposed continuous process with mixer-settler extractors. 

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