An effective, simple method has been developed for the recovery of ZnO and ZnS nanoparticles from hazardous phosphor ash waste. Experimentally, zinc (77%) in the phosphor ash (that contains mainly zinc (91%)) can be recovered by extraction with a room temperature ionic liquid (RTIL) ([C4mim] [PF6], 1-butyl-3-methylimidazolium hexafluorophosphate). Component fitted X-ray absorption near edge structure (XANES) spectra of zinc indicate that metallic zinc (Zn) (9%) in the phosphor ash can be dissolved to form a Zn2+1-methylimidazole ([mim]) complex during extraction with the RTIL. ZnS and ZnO nanoparticles (6061%) can also be extracted from the phosphor. Over the 298523 K temperature range, desired ZnO/ZnS ratios (0.30.6) can be obtained since interconversion of ZnS to ZnO in the RTIL is temperature dependent. The Fourier transformed extended X-ray absorption fine structure (EXAFS) data also show that the nanosize ZnS extracted in the RTIL possesses a ZnS bond distance of 2.33 with coordination numbers (CNs) of 3.63.7. At 523 K, in the RTIL, ∼30% of the ZnS is oxidised to form octahedral ZnO (with a bond distance of 2.10 and a CN of 6.1) that may coat the surfaces of the ZnS nanoparticles. This work exemplifies the utilisation of X-ray absorption spectroscopy (EXAFS and XANES) to reveal speciation and possible reaction pathways in a nanoparticle extraction process (with a RTIL) in detail.
All Science Journal Classification (ASJC) codes
- Chemistry (miscellaneous)
- Environmental Chemistry
- Geochemistry and Petrology