Extraction kinetics of tantalum by MIBK from pulp using Lewis cell

The kinetics of the forward extraction of TaF72 − by MIBK from stock was investigated using a Lewis cell. Different parameters such as the tantalum concentration, fluoride ion concentration, hydrogen ion concentration, and MIBK concentration, as well as extracting temperature were studied separately to examine their effect on the extraction rate of TaF72 −, and a rate equation was deduced based on the analysis. The experimental results demonstrate that the rate of TaF72 − extraction is controlled by a chemical reaction at the interface rather than in the bulk phase. Further analysis suggests that the TaF72 − extraction rate is first order with respect to MIBK concentration, hydrogen ion concentration, and tantalum concentration, and zero order with respect to fluoride ion concentration, respectively. The mechanism of TaF72 − extraction is controlled by the slow distribution of the H·MIBK+ at the interface to form HTaF7·MIBK−(i) between the pulp phase and the interface.

► The kinetics of the direct extraction of tantalum by MIBK was determined.
► The extraction rate constant, kf, is 10− 2.35 ± 0.1.
► The mass transfer flux was determined.
► The rate determining step was identified.
► Values of Ea, Δ‡H°, Δ‡S°, and Δ‡G° were determined.