Abstract
Iron (Fe), cobalt (Co) and nickel (Ni) together are known as the iron triad exhibiting similar chemical and physical affinities in the periodic table. We have developed a green, efficient, highly selective, environmentally benign, water-IL biphasic solvent extraction system for the selective extraction of iron triad elements from their aqueous mixtures at room temperature using a new salicylate functionalized imidazolium based task specific ionic liquid (TSIL) i.e. 1,3-dioctylimidazolium 2-hydroxybenzoate [DOIM][OHB]. Co2+ was extracted within 5 min as a blue complex while the residual mixture was allowed to stand overnight. In the meantime, Fe2+ was oxidized to Fe3+ without using any additional oxidants and was extracted as a red coloured complex. Ni2+ was not observed visibly, however atomic absorption spectroscopy (AAS) indicated the presence of less than 1% Ni2+. The extraction of heavy metal ions follows neutral extraction mechanism elucidated through UV visible spectroscopy.
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•Selective Extraction of heavy metals using TSIL.•No additional oxidants or salting out agent used.•Neutral extraction mechanism occurs due to hydrophobicity of TSIL.•Stripping of metal ions with aqueous ammonia.•Recyclability and re-use of TSIL.