SUPERCRITICAL-FLUID EXTRACTION OF ORGANIC AND INORGANIC MERCURY FROM SOLID MATERIALS

Mercuric ions (Hg2+) can be extracted from solid samples (cellulose ma trix) using methanol modified supercritical CO2 containing the fluorin ated chelating agent lithium bis(trifluoroethyl)dithiocarbamate (LiFDD C). Methylmercuric chloride (CH3HgCl) and dimethylmercury [(CH3)2Hg] c an be extracted by supercritical CO2 without chelating agent and modif ier. The solubility of Hg(FDDC)2 in supercritical CO2 has been determi ned to be 5 x 10(-3) M at 50-degrees-C and 150 atm, which is about 3 o rders of magnitude greater than that of the non-fluorinated analogue H g(DDC)2. Use of methanol (5%)-modified CO2 further enhances the solubi lity of Hg(FDDC)2 by a factor of 2.4. A small amount of water added to the sample matrix tends to facilitate the extraction of Hg(FDDC)2 and CH3HgCl. Potential applications of this in situ chelation-supercritic al fluid extraction method for the preconcentration of mercury species and treatment of mercury contaminated wastes are discussed.