EXTRACTION OF CARBOXYLIC-ACIDS WITH TERTIARY AND QUATERNARY AMINES - EFFECT OF PH

Extractions of carboxylic acids by tertiary and quaternary amines were studied under various equilibrium pHs ranging from 2.0 to 8.5. The quaternary amine Aliquat 336 extracted both dissociated and undissociated forms of acids, whereas the tertiary amine Alamine 336 extracted only the undissociated acid. Pure Aliquat 336 also had higher distribution coefficients, K(D), than Alamine 336 at all pHs. In the intermediate pH range, K(D) decreased with increasing the equilibrium pH of the aqueous phase. However, in the extremely high and low pH ranges, K(D) remained unchanged with pH. This pH dependency of K(D) can be modeled by using a three-parameter equation derived from general chemistry principles. Extractions were also conducted with two diluents, kerosene and 2-octanol. In general, the polar diluent, 2-octanol, increased the extracting power of Alamine 336 by providing more solvating capacity for the nonpolar amine. In contrast, neither the polar nor the nonpolar diluent was active when used with Aliquat 336.