Extraction of fission palladium by Aliquat 336 and electrochemical studies on direct recovery from ionic liquid phase

The wide electrochemical window and ion exchange properties of a room-temperature ionic liquid (RTIL) have been exploited for the extraction of palladium from nitric acid medium into ionic liquid phase — followed by direct electrodeposition of the metal from the organic phase. Extraction of palladium by commercial Aliquat 336 ionic liquids, tri-n-octylmethylammonium chloride (TOMAC) and tri-n-octylmethylammonium nitrate (TOMAN), was studied as a function of [HNO3], [NO3−] and [TOMAN]. The distribution ratio (DPd(II)) of palladium in TOMAN increased with an increase in the concentration of nitric acid and passed through a maximum at 1.0 M nitric acid. In contrast, the DPd(II) value of palladium in TOMAC decreased continuously with an increase in the concentration of nitric acid. Substantial amounts of water and nitric acid were also co-extracted into the organic phase with palladium. dox behavior of a solution of Pd2+ extracted in 0.1 M TOMAN/CHCl3 and 0.1 M TOMAC/CHCl3 at glassy carbon working electrode was studied using cyclic voltammetry. The voltammogram consisted of a single reduction and an oxidation wave indicating that Pd2+ was reduced to palladium metal by a single-step two-electron transfer at the working electrode. Controlled potential deposition of palladium on platinum electrode gave a black deposit, which was characterized to be metallic palladium. Interference of other fission products during extraction and electrodeposition of palladium is also reported.