A method of extracting metalloid and metal species from a solid or liquid material by exposing the material to a fluid solvent, particularly supercritical carbon dioxide, containing a chelating agent is described. The chelating agent forms chelates that are soluble in the fluid to allow removal of the species from the material. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent comprises a trialkyl phosphate, a triaryl phosphate, a trialkylphosphine oxide, a triarylphosphine oxide, or mixtures thereof. The method provides an environmentally benign process for removing contaminants from industrial waste. The method is particularly useful for extracting actinides from acidic solutions, and the process can be aided by the addition of nitrate salts. The chelate and supercritical fluid can be regenerated, and the contaminant species recovered, to provide an economic, efficient process.
ACKNOWLEDGEMENT OF GOVERNMENT SUPPORT
This invention was funded in part by (1) the United States Department of Energy, under Special Master Task research, Subcontract No. C85-110554, (2) a grant from DOE Idaho Field Office under the Office of Technology Development's Innovative Technology Department Program and by NSF-Idaho EPSCOR Program under NSF Cooperative Agreement OSR-9350539, and (3) the National Science Foundation, under Grant RII-8902065. The United States Government may have certain rights in this invention as a result of these grants.