Selective Cobalt over Nickel separation using neat and confined ionic liquids

Abstract

Task Specific Ionic Liquids (TSILs) generated by association between tetraalkylammonium cations and coordinating anions such as dicyanamide (Dca -) and thiocyanate (SCN -) were used for the selective separation of Ni(II) over Co(II). SCN-based TSIL presents higher extraction efficiency than the Dca-based one towards Co(II) (E = 85.4 % vs 54.6 %) and Ni (II) (E = 22 % vs 0.5%) but lower separation factors (Co/Ni = 21 vs 239). Interestingly, extraction of Co (II) and Ni(II) in Dca-based TSIL can be enhanced using salts with chaotropic anions such as NaNO3 (E > 90 % for Co(II) and E = 85% for Ni(II)). The use of NaCl allows, moreover, the efficient separation of both ions with Co/Ni >1000. The metal can be recovered from the IL phase using Na2SO4 aqueous solution to limit the release of the IL and to ensure a good recyclability of this latter. The confinement of TSIL in silica -matrix ionogel constitutes a valuable method to improve the handling of the IL. Indeed, the extraction properties of the ionogel containing [THN][Dca] IL are very close to those obtained using the same neat IL with an efficient separation of Co(II) over Ni(II) in NaCl 4 mol.L -1 (Co/Ni >1000). Finally, the recyclability of the ionogel was studied and found comparable to that of neat IL.

Ionogels as modular platform for metal extraction

“…In our previous work [28], different extraction cycles and which progressively decreases the coordinating anion content of the material affecting its extraction properties. This is the reason why, in this work, we have developed ionogels starting from the commercial salt, tetrahexylammonium bromide [THN][Br] to avoid anionic metathesis.…”

“…Extraction experiments using pure IL phases are performed under the same conditions as those described in our previous articles. [28] 3. Results and discussion…”

“…In a previous work, we explored a new strategy to develop an adsorbent material consisting of confining a TSIL in a silica gel matrix. [28] (Boudesocque et al, 2019). This elegant strategy is also a way to avoid problems that may occurred during ionogels synthesis.…”

Single-Stage Extraction and Separation of Co2+ from Ni2+ Using Ionic Liquid of [C4H9NH3][Cyanex 272]

“…The multicomponent mixtures of metal ions, e.g., Co 2+ , Ni 2+ , Mn 2+ , Al 3+ , Zn 2+ , and others, are coexisting in the leaching solutions [ 4 ]. Efficient separation of Co 2+ from leaching solution containing Ni 2+ is the key technology for the final preparation of high-purity cobalt or nickel products [ 7 , 8 ].…”

Coordination of the Co2+ and Ni2+ Ions in Tf2N– Based Ionic Liquids: A Combined X-ray Absorption and Molecular Dynamics Study

“…The use of ILs in the simultaneous recovery of cobalt and nickel from aqueous solutions has been investigated in several recent studies aimed at developing more sustainable separation processes either using the “neat” ILs or in the presence of auxiliary extracting ligands. ,− …”