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Fluid extraction using carbon dioxide and organophosphorus chelating agents

United States Patent

5,840,193
November 24, 1998
View the Complete Patent at the US Patent & Trademark Office
Methods for extracting metalloid and metal species from a solid or liquid material by exposing the material to a fluid solvent, particularly supercritical CO.sub.2, and a chelating agent are described. The chelating agent forms a chelate with the species, the chelate being soluble in the fluid to allow removal of the species from the material. In preferred embodiments the extraction solvent is supercritical CO.sub.2 and the chelating agent comprises an organophosphorous chelating agent, particularly sulfur-containing organophosphorous chelating agents, including mixtures of chelating agents. Examples of chelating agents include monothiophosphinic acid, di-thiophosphinic acid, phosphine sulfite, phosphorothioic acid, and mixtures thereof. The method provides an environmentally benign process for removing metal and metalloids from industrial waste solutions, particularly acidic solutions. Both the chelate and the supercritical fluid can be regenerated and the contaminant species recovered to provide an economic, efficient process.
Smart; Neil G. (Moscow, ID), Wai; Chien M. (Moscow, ID), Lin; Yuehe (Moscow, ID), Kwang; Yak Hwa (Moscow, ID)
Idaho Research Foundation (Moscow, ID)
08/ 686,422
July 26, 1996
ACKNOWLEDGEMENT OF GOVERNMENT SUPPORT This invention was funded in part by the United States Department of Energy under Grant CC-S-588193-002-C; the United States government has certain rights in the invention.