PHASE BEHAVIOR AND REVERSE MICELLE FORMATION IN SUPERCRITICAL CO_2 WITH DTAB AND F-PENTANOL FOR DECONTAMINATION OF RADIOACTIVE WASTES

摘要

To develop a metal separation method using supercritical CO_2 (scCO_2) solvent for the decontamination process of radioactive wastes, the reverse micelle formation in scCO_2 was investigated. Dodecyltrimethylammonium bromide (DTAB) as a surfactant to form the reverse micelles and 2,2,3,3,4,4,5,5-octafluoro-1-pentanol (F-pentanol) as a modifier to increase the solubility of DTAB into scCO_2 were used. The reverse micelles could be formed by using 0.02 mol/dm~3 DTAB and 0.45 mol/dm~3 F-pentanol. A water concentration dissolved in scCO_2 was increased with an increase of pressure, and 0.42 mol/dm~3 water, which was 3 times larger than that in the neat CO_2, could be dissolved in scCO_2 at 38 MPa. Moreover, 0.1 mol/dm~3 HNO_3 could dissolve at the same pressure as water. On the other hand, it was found that the solubility of water at outside of reverse micelles increased with F-pentanol. The ratio of water and F-pentanol affected the phase behavior of water in scCO_2.