Individual metal recovery and separation by solvent extraction has been an important technique in pollution control as well as in hydrometallurgical processes. Synergistic extraction and separation of two cations, e.g., Cu(II) and Zn(II), a cation and an anion, e.g., Cu(II) and Cr(VI), and two cations and one anion, such as Cu(II), Zn(II), and Cr(VI), have been demonstrated employing a novel hydrophobic microporous hollow fiber membrane-based (HFM) extraction technique. The extraction selectivity of Cu(II) and Zn(II) by LIX 84 (anti-2-hydroxy-5-nonylacetophenone oxime) and bis(2-ethylhexyl)phosphoric acid (D2EHPA), respectively, in a two-fiber-set HFM extractor is significantly enhanced due to competitive extraction. The efficiencies of extraction of Cu(II) and Cr(VI) by LIX 84 and tri-n-octylamine (TOA), respectively, are increased due to the self-control of the aqueous feed pH. A simplified mathematical model for synergistic extraction of Cu(II) and Zn(II) has been developed. The model predicts the observed extraction and separation performance well. In the novel HFM extractor, the extraction rates of Zn(II) and Cu(II) by D2EHPA and LIX 84, respectively, were controlled by the aqueous and organic boundary layer resistances as well as the interfacial reaction resistances.

Many wastewaters as well as aqueous solutions used for hydrometallurgical extractions have multiple toxic heavy metals:  some are present as cations; others are present as anions. This research is directed toward extracting multiple heavy metallic species simultaneously into an appropriate mixed solvent and then recovering and concentrating such heavy metals into appropriate aqueous stripping solutions. Heavy metals of interest are Cu(II), Cr(VI), Zn(II), Hg(II), etc. Such processes have been carried out in a nondispersive fashion in microporous hydrophobic hollow fiber membrane-based devices containing multiple sets of fibers. The results will be presented, and the basis of the observed synergism will be discussed. The advantages of such extraction-stripping processes will be pointed out.

No abstract

A solvent mixture of 1-hexanol and butyl acetate has been successfully used for the extraction of penicillin G. This solvent mixture may not only synergistically and effectively extract penicillin G, but also inhibit emulsion formation during the extraction of penicillin G from the filtrate of the fermentation broth. The equilibrium constants of the extraction, the molar ratios of 1-hexanol and penicillin G in the extracted species and the synergistic extraction of penicillin G have been studied by chemical analysis and by monitoring the absorbency shift in the FT-IR spectra of the functional groups in the solvents.

No abstract