Ea. Saad, Kinetic studies of the extraction of Cd-115(II) by a mixture of diphenylcarbazone and 1,10-phenanthroline in benzene, MICROCHEM J, 64(1), 2000, pp. 27-31
The rate of extraction of Cd-115(II) from an aqueous phase at constant ioni
c strength of 0.1 M (H+, NaClO4) and pH = 8.5, t = 25 degrees C by a mixtur
e of diphenylcarbazone (DPC) and 1,10-phenthroline (phen) in benzene has be
en studied using a stirred Lewis cell. The obtained first order rate consta
nts showed that the rate of extraction increases with the increase in [DPC]
and [phen], while it decreases with the increase in [H+]. A plot of K-obs
vs. 1/[H+] yielded a straight line, from the slope and intercept of this li
ne the values of the rate constants K-HLs and K-LS were calculated and foun
d to be equal: K-HLS = 1.71 +/- 1.02 x 10(4) M-1 min(-1) and K-LS = 2.40 +/
- 0.07 x 106 M-1 min(-1) for the extraction of Cd-115(II) by a mixture of (
DPC) and (phen). The suggested mechanism indicates that the mixed complex i
s formed by replacing the water molecule in the metal coordination sphere b
y the synergistic ligand. Activation parameters E*, Delta H*, and Delta S*
are calculated and the result confirmed our suggested mechanism. (C) 2000 E
lsevier Science B.V. All rights reserved.