Kinetics of Forward Extraction of V(V) in V(V)-NO₃^- (H⁺, Na⁺)-TOA-Kerosene System using Single Drop Technique

Abstract

The titled system has been investigated using a single drop technique and flux (F) method of data treatment. In calculating fluxes, the time for drop formation and coalescence (?t = 0.75 s) is considered. At lower concentration region of vanadium, V(V), the rate of V(V) transfer is directly proportional to its concentration. With the increase in [V(V)], slowly extractable V(V) species are formed gradually resulting in decrease in rate. Rate is directly proportional to the square root of [TOA]. It is reported that the most favorable extractable V(V) species exists in maximum amount at pH 2, and so, log F vs pH plots show a maximum at pH~2. The flux of V(V) transfer in most cases is found to be decreased with increasing [NO₃^-]. Reaction orders with respect to [V(V)], pH and [NO₃^-] have been attempted to be estimated, but in vein due to non-linearity of plots in most cases. Activation energies for the present system is ~ -12 kJ/mol. This is unexpected but explained. Due to irregular variation of the composition of extractable species with [V(V)], [H⁺]; as well as temperature; it is not possible to elucidate the value of rate constant (k) and mechanism in simple way.