The Extraction of Metal Contaminants Using Supercritical Carbon Dioxide

Abstract

Conventional decontamination methods utilize water-based systems, which generate high amounts of secondary wastes. Herein, the authors describe an environmentally benign decontamination method using liquid and supercritical CO2. The use of CO2 as a solvent affords effective waste reduction by its ability to be recycled, thereby leaving behind only the contaminants upon its evaporation. In this study, a CO2 solution process was assessed using t-butyl salen (t-salen), dicyclohexano-18Crown6 (DC18C6), 8-hydroxyquinoline (8-HQN), perfluoro-1-octanesulfonic acid tetra-ethylammonium salt (NEt4PFOSA), and pentadecafluorooctanoic acid ammonium salt (NEt4PFOA) to extract spiked radioactive contaminants (Nb, Zr, Co, Sr) from an inert sample matrix, namely with filter paper. With the static extraction method, Sr was extracted with a maximum extraction rate of 97%, and Nb was extracted with a maximum extraction rate of 75%. Additionally, the authors were also able to extract Co and Zr with maximum extraction rates of 73% and 64%, respectively.