Extraction of Cd(II) picrate with benzo-18-crown-6 ether into benzene under the presence of nitric acid in water phases.

Cd(II) picrate was extracted at 298 K into benzene (Bz) using benzo-18-crown-6 ether (B18C6) under the presence of HNO3 in water (w) phases. Extraction constants, such as Kex, Kex±, and Kex2±, and a conditional distribution constant (KD,A) of A- = Pic- were determined, where their extraction and distribution constants were defined as [CdLA2]Bz/P, [CdLA+]Bz[A-]Bz/P, and [CdL2+]Bz([A-]Bz)2/P with P = [Cd2+][L]Bz[A-]2 at L = B18C6 and [A-]Bz/[A-], respectively. A [HNO3]t dependence of log Kex was discussed, while ionic strength dependences of log Kex± and log Kex2± were done. Here, [HNO3]t denotes a total concentration of HNO3 added to the w phases. Also, among the eight conditions of [HNO3]t, comparing Kex with an experimental distribution ratio of Cd(II) indicated that the Kex values do not function as a measure for extraction ability of L to the present systems. Moreover, the composition of Cd(II): Pic(-I) in the extracted species was shown by changing [HNO3]t.