Extraction of Cupric Ions with Ionic Liquids Containing Polypyridine-type Small Molecules or Peripherally Pyridine-modified Dendrimers

The hydrophobic ionic liquid N-butyl-N-methylpyrrolidinium bis((- trifluoromethyl)sulfonyl)amide (BMP- TFSA IL), which contains a series of flexible ionophores of polypyridine- type small molecules or two rigid iono- phores of peripherally pyridine-modi- fied PAMAM dendrimers, was used to extract cupric ions from aqueous solu- tions. The polypyridine-type iono- phores show good selectivity toward cupric ions at pH 2. The selectivity is affected by the spacing between the two amino groups. However, the pyri- dine-modified dendrimers showed poor selectivity, although their extraction ef- ficiency still depended on the pH of the aqueous solution. The ionic liquids that contained small molecular iono- phores and their dendrimer analogs were reused after acid washing or elec- trochemical reduction. During acid washing, the nitrogen atoms of the ion- ophores were protonated to release the cupric ions into the aqueous phase, and the copper atoms were deposited onto the electrode surface during the elec- trochemical reduction accompanied by the regeneration of the ionophores.