Extraction of Cu²⁺ in Aqueous Solution With Room-temperature Ionic Liquids

The extraction capability of Cu²⁺ in aqueous solution with imidazolium ionic liquids,BmimPF₆,HmimPF₆,and omimPF₆,was studied in this research.It was found that the extraction efficiency for Cu²⁺ was quite low when only imidazaolium ionic liquids was used as extractant.On the other hand,with the addition of ditizone,the extraction efficiency for Cu²⁺ was enhanced from 2.1% to 93.1%,which was much higher compared to CCl₄ extraction system.Meanwhile,the extraction efficiency for Cu²⁺ decreased with the increase of the alkyl chain length of the imidazolium cations.The effects of temperature,pH value,extraction time and salt effect were also studied.The temperature had no significant impact on the extraction efficiency,and extraction equilibration was reached within 6 minutes.The extraction efficiency strongly depended on the solution pH.It was 5.7% at pH<2,whereas it could be above 90% at pH>10.The addition of salts into the solution lowered the extraction efficiency.