Выделение соединений хрома из ZSM-5 в ионную жидкость

The speciation of extracted chromium from ZSM-5 into an ionic liquid (IL) was studied using X-ray absorption near-edge structure (XANES) spectroscopy. The main adsorbed chromium species in ZSM-5 were Cr(VI)-HA (Cr(VI) chelated with humic acids (HAs)) (57%), Cr(VI) ads (Cr(VI) adsorbed on ZSM-5) (33%), and Cr(III)-HA (Cr(III) chelated with HA) (10%). In this work, l-butyl-3-methylimidazolium chloride ([C 4 mim]Cl), was used as the IL to extract the chromium compounds from ZSM-5. Experimentally, approximately 75% of the chromium compounds were extracted within 30 min at 343 K. Combining the chromium extraction efficiency and component fitting results of the XANES spectra, almost all of Cr(VI)-HA was extracted into [C 4 mim]Cl. Following extraction, 34.5% of the Cr(VI) compounds were reduced to form Cr(III)-HA and Cr(III) ions. The Cr-O bond distance of Cr compounds was 1.69 A in [C 4 mim]Cl as shown by X-ray absorption fine structure (EXAFS) spectroscopy. 1 H nuclear magnetic resonance (NMR) showed that the reduction and extraction of Cr(VI) compounds were affected by [C 4 mim] + . The non-extractable chromium species in ZSM-5 were Cr(VI) ads (9%), Cr(III)-HA (10.8%), and Cr(III) ads (5.2%). The fraction of Cr(VI) was decreased greatly because of the use of [C4mim]Cl as the extractant.