| abstract |
A method of extracting metalloid and metal species from a solid or liquid material by exposing the material to a supercritical fluid sol-vent containing a chelating agent is described. The chelating agent forms chelates that are solu-ble in the supercritical fluid to allow removal of the species from the material. In preferred em-bodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is a fluo-rinated .beta.-diketone. In especially preferred em-bodiments the extraction solvent is supercritical carbon dioxide, and the chelating agent com-prises a fluorinated .beta.-diketone and a trialkyl phosphate, or a fluorinated .beta.-diketone and a tri-alkylphosphine oxide. Although a trialkyl phos-phate can extract lanthanides and actinides from acidic solutions, a binary mixture comprising a fluorinated .beta.-diketone and a trialkyl phosphate or a trialkylphosphine oxide tends to enhance the extraction efficiencies for actinides and lan-thanides. The method provides an environmen-tally benign process for removing contaminants from industrial waste without using acids or bi-ologically harmful solvents. The method is par-ticularly useful for extracting actinides and lan-tanides from acidic solutions. The chelate and supercritical fluid can be regenerated, and the contaminant species recovered, to provide an economic, efficient process. |