CATALYTIC ROLE OF A WATER-IMMISCIBLE ORGANIC-ACID ON AMINE EXTRACTIONOF CITRIC-ACID FROM AQUEOUS-SOLUTIONS

The effect of a water-immiscible organic acid on the kinetics and mech anism in the extraction of citric acid from aqueous solutions with tri -n-octylamine was studied in the temperature range of 298-328 K. The w idely used acidic metal extractant bis(2-ethylhexyl)phosphoric acid (D 2EHPA) was selected as the model organic acid. Although citric acid wa s not extractable with D2EHPA alone, it was shown that the presence of D2EHPA could accelerate both rates of forward extraction and back ext raction for the title system under the conditions studied. The rate eq uations for the formation and dissociation of citric acid-amine comple xes were obtained, and a possible reaction mechanism was proposed and discussed. In addition, the effect of temperature on the reaction kine tics was examined and the activation energies were determined.