Type II ELM

Emulsion liquid membrane extraction of cephalosporins conform to the type II facilitated transport. Here the solute transport is either associated with a cotransport or counter-transport of an anionic species depending on whether ion-pair or ion-exchange extraction is exploited in the ELM system. 

Izatt et al. (112) discuss the ELM extraction of metal ions from aqueous source phases where the metal ion is present as a complex anion or as a neutral complex using macrocyclic polyether carriers. The parameters of co-anion type and metal ion concentration are varied to tailor the selectivity of the separation. Experimental data for the separation of Cd(II) from Zn(II) and/or Hg(ll), Au(I) from Ag(I), and Au(III) from Pd(II) or Ag(I) are given to illustrate the application of this technique. The experimental data are discussed in terms of various thermodynamic parameters. 

Due to their high efficiency, ELMs would appear to be attractive alternatives to SLMs. However ELM systems often suffer from problems of low solubility and difficulties with de-emulsification. To overcome these problems, a new liquid membrane process, the emulsion free liquid membrane (EI M), was developed by Kumar ef al. (60). Application of this novel technique to hydrometallurgical processes is quite promising (67). Recent studies of separating heavy metals, such as Cr(VI) and Cu(II) from electroplating effluents, with an EFLM system indicate that the technique is very efficient and superior to other types of LMs. 

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