Extraction of nanosize copper pollutants with an ionic liquid

Speciation and possible reaction paths of nanosize copper pollutants extracted with a RTIL (room-temperature ionic liquid ([C₄mim][PF ₆], 1-butyl-3-methylimidazolium hexafluorophosphate)) have been studied in the present work. Experimentally, in a very short contact time (2 min), 80-95% of nanosize CuO as well as other forms of copper (such as nanosize Cu, Cu²⁺, or Cu(II)(ads) (in the channels of MCM-41)) in the samples could be extracted into the RTIL The main copper species extracted in the RTIL as observed by XANES (X-ray absorption near edge structure) were Cu(II). Existence of Cu-N bondings with coordination numbers (CNs) of 3-4 for copper extracted in the RTIL was found by EXAFS (extended X-ray absorption fine structural) spectroscopy. Interestingly, chelation of Cu(II) with 1-methylimidazole (MIm) in the RTIL during extraction was also observed by ¹H NMR (nuclear magnetic resonance). At least two possible reaction paths for the rapid extraction of nanosize copper pollutants with the RTIL might occur: (1) an enhanced dissolution of nanosize CuO (to form Cu²⁺) and (2) formation of [Cu(Mlm)₄(H₂O)₂] ²⁺ that acted as a carrier of copper into the RTIL matrix.