Kinetic studies of the extraction of Cd-115(II) by a mixture of diphenylcarbazone and 1,10-phenanthroline in benzene

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.