We found that a calixarene-bearing pyridine is soluble in a typical room-temperature ionic liquid (RTIL), 1-alkyl-3-methylimidazolium hexafluorophosphate. Pyridinocalixarene showed a high extraction ability and selectivity for silver ions. The extraction performance of the calixarene was greatly enhanced by dissolution in RTILs compared to in chloroform. In a competitive extraction test using five different metal ions (Ag+, Cu2+, Zn2+, Co2+, Ni2+), only silver ions were transferred by the calixarene from the aqueous feed phase into the RTILs, through a cation-exchange mechanism. The pyridinocalixarene was found to form a stable 1:1 complex with silver ions, both by slope analysis and by Job's method. Since it is easy to strip silver ions from RTILs by controlling the aqueous-phase pH, the extraction performance of calixarene in RTILs was maintained after five repeated uses.
All Science Journal Classification (ASJC) codes
- Analytical Chemistry