KINETICS AND MECHANISM OF FORWARD EXTRACTION OF MN(II) FROM SULFATE-ACETATO MEDIUM BY CYANEX 272 DISSOLVED IN KEROSENE USING THE SINGLE-DROP TECHNIQUE

Abstract

The flux of Mn(II) transfer in -Cyanex 272-kerosene system was investigated using the single-drop technique and the flux method of data treatment. The empirical flux equation at 303 K is: F f = 10−3.6 [Mn(II)] (1 + 104.5 [H+])−1 (1 + 1.58 [])−1. The activation energy (E a ) varies within 15–59 kJ/mol depending on experimental conditions. On analyzing the flux equation and with the help of E a values, it is concluded that either the extraction reaction step Mn2+ + A− → MnA+ or the diffusion of reactants (or products) to (or from) the reaction site is rate controlling depending on the reaction parameters. At high pH and at intermediate pH-higher temperature regions, low E a (≤20 kJ/mol) suggests that the process is under diffusion control. But at low pH and at intermediate pH-lower temperature regions, high E a (≥50 kJ/mol) suggests that the process is under chemical control. High negative ΔS ± value indicates that the slow extraction reaction step occurs by means of an SN2 mechanism.