Chapter 2 - Principles of Solvent Extraction of Organic and Mineral Acids

Abstract

This chapter discusses the principles of solvent extraction of organic and mineral acids. Recovery and concentration of organic acids, as well as separation of acid mixtures, have attracted great interest among researchers, especially in connection with their recovery from fermentation broths, reaction mixtures, and waste solutions. Extraction of acetic, propanoic, lactic, tartaric, succinic, and citric acids has received more attention because of its industrial importance. Most of them are freely soluble in water, some in alcohols, and some in polar solvents. Extraction chemistry is concerned solely with the state of equilibrium in multicomponent heterogeneous systems. In addition the chapter also emphasis that the extraction of carboxylic acids is presented according to three extraction categories that are as follows: first, extraction by solvation with carbon-bonded oxygen-bearing extractants; second, acid extraction by solvation with phosphorus-bonded oxygen-bearing extractants; and third, extraction by proton transfer or by ion-pair formation, with extractants being high-molecular-weight aliphatic amines. The first two categories involve the solvation of the acid by donor bonds of some kind, which are to be distinguished from strong covalent bonds and from ionic interactions. The latter is the reaction involved in the third extraction category. The extraction mechanism determines the effects of various parameters on extraction efficiency and selectivity.