Separation and concentration of cobalt from zinc plant acidic thiocyanate leach solutions containing cobalt and nickel by an emulsion liquid membrane using triisooctylamine as carrier

Separation of Co(II) from Zinc Plant Acidic Thiocyanate Leach Solutions Containing Co(II) and Ni(II) by Solvent Extraction Using Trioctylamine in Toluene

“…It is therefore concluded that two moles of extractant coordinate the Co(SCN) 4 2-molecule around the Co(II) ion with unshared lone pairs of electrons from the nitrogen atoms of four TOA extractants, retaining the coordination sphere around the metal ion [17]. The species extracted depends on many factors, such as the equilibrium pH, the extractant and metal concentrations, and the solvent phase properties [18].…”

“…, whereas in case of nickel ions they hardly form the thiocyanate complex [22][23][24]. Preston [20] stated that the cobalt is extracted as the tetrahedral anion, Co(SCN) 4 2− , from the examination of electronic spectra of organic extract, while nickel forms an octahedral complex, probably Co(SCN) 4 ·(H 2 O) 2 2− . This is in agreement with the reports of Zhu [4] that the 7d electron of Co 2+ is the one of the most favoured ions for the tetrahedral configuration from the viewpoint of the ligand field theory and that the steric hindrance is the only factor which could weaken the octahedral configuration.…”

“…The maximum extraction (99.9 %) was achieved at 5.0 % TOA in toluene. The extractant concentration in the organic phase played a vital role in the overall extraction of the metal ions because it was necessary for the amine to be sufficiently available for the formation and extraction of the complex (R 3 NH) 2 Co(SCN) 4 …”

“…The purified leach liquors contain both Co(II) and Ni (II) ions. It is very difficult to obtain pure cobalt and nickel compounds from such solutions because of the similar physicochemical properties of these metals [3,4]. Using classical methods, such as precipitation, oxidation, and crystallization, it is impossible to separate the nickel-cobalt pair in a simple and economical way.…”

Studies on the extraction of chromium(III) by emulsion liquid membrane

“…There are only a few reports about the facilitated transport of chromium(III) using TBP as mobile carrier through ELM. There are many studies having been carried out using ELM for the recovery of metal ions [8][9][10][11][12][13][14], aniline [15], phenol [16], organic acids [17], sephalexin from dilute solution [18]. Then there is no available information in the published literatures on the removal study of chromium(III) transport through ELM using TBP as carrier.…”