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

Abstract

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 K_ex, K_ex±, and K_ex2±, and a conditional distribution constant (K_D,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 K_ex was discussed, while ionic strength dependences of log K_ex± and log K_ex2± 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 K_ex with an experimental distribution ratio of Cd(II) indicated that the K_ex 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.

Keywords: Benzene; Benzo-18-crown-6 ether; Cd(II) picrate; Distribution equilibrium potential; Extraction ability; Extraction with nitric acid.