Supercritical Carbon Dioxide Extraction Of Metal Ions From Water

Supercritical Fluid Extraction (SFE) is a kind of newly extract separation technology. It is promising for its non-toxic, low price and easy to find, the moderate critical temperature(31℃) and critical pressure(7.3MPa), then it has realistic meaning to research it. Literatures about SFE these years promote theory study and practical use development. But at the moment, most of effective CO₂-philes reported contain fluorine. These CO₂-philes have lots of defect such as high toxicity, high price and environment unfriendly. Other CO₂-philes reported contain silicon. These CO₂-philes also have defect such as low extraction efficiency and difficult to synthesis. So, design and synthesize a newly nonfluorous chelating ligands is the key of development of supercritical fluid extraction.Due to literatures reported and relation between structure and performance, we designed and synthesized a series of novel CO₂-philic compounds starting from cheap and easily available diacetone-D-glucose via simple procedure with high yield A series of new CO₂-philic glucose derivatives containing bis-β-diketone-like functional group, that is bis- acetoacetyl group, via simple procedure with high yield. To the best of our knowledge, all the compounds are new and their structures were confirmed by IR, 1H NMR, 13C NMR and elementary analysis.Solubility of newly-synthesized compounds tests in SCCO₂ were carried out. It is demonstrate that these compounds have high solubility in SCCO₂ when pressure between 90-130Mpa. According to the solubility sequence, We assumed that the ether oxygen and benzylic hydrogens next to the ether oxygen enhance the solubility of compound through specific Lewis acid-base interactions with CO₂. Furthermore, the higher solubility of compound with electron-withdrawing substituent on the benzene ring could be attributed to the higher acidity of benzylic hydrogen and the subsequent stronger interaction with CO₂.Newly synthesized glucose derivatives have been used as chelating reagents to extract metal ions with and without PFOAT(perfluoro-1-octanesulfonic acid tetraethylammonium salt) as aaddictive in supercritical carbon dioxide. The result shows without addictive the extraction efficiencies were low or negligibly small, but with addictive, recovery of metal ions increased significantly. Although the system of glucose derivative, deionized water and PFOAT showed no high percent recovery for metal ions extraction in SCCO₂, but good selectivityfor Sr2+ and Pb2+ has been performed.