Lösungsmittel-Auswahl bei der Flüssig/Flüssig-Extraktion unter physikalisch-chemischen Aspekten

Selection of solvents in liquid-liquid extraction according to physico-chemical aspects . Selection of appropriate solvents for liquid-liquid extraction is frequently necessary in process design. High selectivity and capacity are important, but not the only considerations in choosing suitable solvents. In comparing the various solvents, their selectivity and capacity should be examined at infinite dilution of the solute in the solvent. The required limiting activity coefficients may be estimated if no experimental data are available. A preselection of solvents may be accomplished by considering the interactions of the molecules. There are certain parameters quantifying the ability of the components to interact. Therefore, a selection based merely on dielectric constants or solubility parameters is hardly conclusive.     

Keramische Membran zur Wasserabtrennung aus Lösungsmitteln

Novel hydrophilic SiO_x modified alumina membranes with high separation factors and flux rates have been prepared for the separation of water from organic solvents. The membranes are prepared by the deposition of SiO_x networks inside the γ‐Al₂O₃ layer of a commercial ultrafiltration membrane by hydrolysis of tetraethylorthosilicate in autoclaves at 250°C. The transport resistance of the individual membrane layers to the permeation flux are described by a model. The membranes are stable towards solvents up to at least 150°C. Pervaporation studies show that water can be separated from solvents like acetonitrile, tetrahydrofuran, 2‐isopropanol, ethanol, dimethylsulfoxide, dimethylformamide, phenol. The separation performance of the membranes allows their use in technical separation processes, especially for the remove of water.     

Flüssig/Flüssig-Extraktion: Einsatzgebiete und Lösungsmittel-Auswahl

Liquid/liquid extraction: Applications and choice of solvent . The significance of liquid/liquid extraction has been steadily increasing in recent years as more and more stringent demands are made on the purity, availability, and environmental safety of chemical products. The use and success of this separation process are critically dependent upon the choice of the right extraction agent. Whereas solvent choice was previously mainly empirical, it is now possible to establish the suitability of a given solvent with the aid of molecular-thermodynamic data. This is demonstrated for the extraction of aromatic compounds. The article closes with an account of the formation and stability of emulsions.     

Grenzbelastung von unpulsierten Füllkörper-Kolonnen bei der Flüssig/Flüssig-Extraktion

Determination of the Limit Load of Non-pulsated Packed Columns for Liquid-Liquid Extraction. Mersmann developed a flood point diagram to determine the limit load of different types of extractors. This contains the rising or falling velocity of an individual droplet as the intermediate quantity. In the flood point diagram valid for packed columns, there is a shaded area of possible load limits instead of a loading curve. In this paper statements about the limit of load of non-pulsated packed columns are focussed by giving a limit line for the mass transfer direction C → D and another for that of D → C. Both the limit lines are within the shaded area given by Mersmann. In the modified flood point diagram, a new relationship for the rising or falling velocity of the individual droplets in a packed bed is used as the intermediate quantity. The validity of this has already been proved for gas-liquid systems.     

Flüssig/Flüssig‐Extraktion von Indium aus sauren Lösungen

The extraction of indium from a synthetic sulfate‐containing solution using commercial reagents (Cyanex 272, DEHPA, and Cyanex 923) is evaluated on a comparative basis. The extraction profiles of indium (III) were examined with regard to the reagent concentration, the pH value of the aqueous solution, and the indium concentration in a low phase ratio of 1:10. DEHPA and Cyanex 272 are, in contrast to Cyanex 923, very well suited for the extraction of indium. Re‐extraction with HCl and H₂SO₄ is compared.