Solvent Extraction of Palladium(II) and Platinum(IV) with N,N-Dioctylsuccinamic Acid from Aqueous Chloride Media

Abstract

Abstract N,N-Dioctylsuccinamic acid was synthesized to examine the selectivity for various metals in extractions from hydrochloric acid. It was found to be highly selective for palladium(II), platinum(IV), and mercury(II) over other base metals including copper(II), nickel(II), cobalt(II), zinc(II), iron(III), aluminum(III), and gallium(III). A quantitative study was conducted on the extraction equilibria of palladium(II) and platinum(IV) from aqueous chloride media with N,N-dioctylsuccinamic acid in toluene, together with measurement of the apparent molecular weight of the extractant. It was elucidated that the extractant (HR) dimerizes in toluene and that palladium(II) and platinum(IV) are extracted according to the following reactions: &PdCl_4^2-+‾H_2R_2 \oversetK_e,Pd\ightleftharpoons ‾PdR_2+2H^++4Cl^- & PtCl_6^2-+‾H_2R_2 \oversetK_e,Pt\ightleftharpoons ‾PtCl_4·2HR+2Cl^- The extraction equilibrium constants of palladium(II) and platinum(IV) with the extractant were evaluated as follows: Ke,Pd=0.11±0.03 (mol·dm−3)5 and Ke,Pt=27.7±3.7 mol·dm−3, respectively.