Asher Vitner

Interactions Between the Components of ABC Extractants and Extraction of Monocarboxylic Acids by These Extractants

Abstract In acid‐base couple (ABC) extractants, the interactions between the lipophilic amines and the lipophilic acids in the organic phase result in the formation of new complexes, some of which involve proton transfer, as indicated by IR spectroscopy. The nature of those interactions is determined by the relative acid‐base properties of the interacting components, their molecular structure, and the properties of the diluent. Extraction of mono‐carboxylic acids (di‐chloro acetic, lactic, and propionic) by various ABC extractants was studied. Ion‐pair formation, H‐bonding, and solvation were found to be the main extraction mechanisms.

Extraction of carboxylic acids by ABC extractants: Effects of temperature, the polarity of the diluent, and the ratio between extractant components

Abstract A study was conducted of the temperature effect on the extraction of lactic and malic acid by acid‐base couple (ABC) extractants in kerosene. Elevating the temperature from 30°C to 80°C decreases the extraction of both acids by ABC extractants comprising tricaprylyl amine (A336). The opposite effect is found for the extraction of lactic acid by primary amine‐containing ABC extractants. It seems that temperature effect in the extraction of lactic and malic acids by ABC extractants results, at least partially, from competition for H‐bonding. The study has also tested the effect of diluent polarity in ABC extractants by replacing kerosene there with octanol. It has shown that increased polarity affects the extraction of carboxylic acids mainly through stabilization of ion pairs and formation of H‐bonds. Another studied effect was that of the ratio between the amine and the lipophilic acid in the ABC extractants. The results were found to depend on the acid‐base properties, polarity, and structure of these components and on the properties of the extracted acid.

Extraction of Dicarboxylic Acids by ABC Extractants

Abstract Extraction of various dicarboxylic acids (maleic, malic, malonic, succinic, and tartaric) by acid–base couple (ABC) extractants was studied. The main extraction mechanisms were found to be ion‐pair and hydrogen‐bond formation. The relative contribution of each mechanism and extraction efficiency were found to be controlled by parameters such as acid–base properties and hydrogen‐bonding capability of the components of the ABC extractants and those of the extracted dicarboxylic acid. Typical ion‐pair formation was observed for extraction of all tested acids with extractants composed of a primary amine and a fatty carboxylic acid. Typical H‐bond formation is shown for extraction of most acids with an extractant composed of a tertiary amine and a di‐ester of phosphoric acid. All other cases had mixed contributions. Strong interactions between the extractant components limited extraction in both mechanisms. The results were also analyzed in comparison with the extraction of monocarboxylic acids. Dicarboxylic acids are better extracted in those cases where the acid–base properties of the system components favor ion‐pair formation. In extraction through H‐bonds, on the other hand, the greater hydrophilicity of the dicarboxylic acids limits the extraction.