Supercritical fluid extraction of organic and inorganic mercury from solid materials.

Abstract Mercuric ions (Hg 2+ ) can be extracted from solid samples (cellulose matrix) using methanol modified supercritical CO 2 containing the fluorinated chelating agent lithium bis(trifluoroethyl)dithiocarbamate (LiFDDC). Methylmercuric chloride (CH 3 HgCl) and dimethylmercury [(CH 3 ) 2 Hg] can be extracted by supercritical CO 2 without chelating agent and modifier. The solubility of Hg(FDDC) 2 in supercritical CO 2 has been determined to be 5 × 10 −3 M at 5O°C and 150 atm, which is about 3 orders of magnitude greater than that of the non-fluorinated analogue Hg(DDC) 2 . Use of methanol (5%)-modified CO 2 further enhances the solubility 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 CH 3 HgCl. Potential applications of this in situ chelation-supercritical fluid extraction method for the preconcentration of mercury species and treatment of mercury contaminated wastes are discussed.