Abstract
When a chlorinated ethylene solvent such as trichloroethylene (TCE) or tetrachloroethylene (PCE) in aqueous solution is adsorbed on activated carbon and then extracted with supercritical carbon dioxide, unlike steam desorption, the recovered solvent may not contain hydrolyzates or water which lead to problems during recycling. However a solvent with high volatility becomes a problem regarding recovery at low pressure of supercritical carbon dioxide. The recovery of solvent by decompressing and cooling was thus studied. Optimal conditions for extraction were 100kg · cm-2 pressure at 35°C, and for recovery, 10kg · cm-2 pressure at -30°C. In the case of TCE, slight dispersion was observed, but carbon dioxide with little dispersed TCE could be compressed and reused for extraction of TCE from activated carbon. For PCE, there was little dispersion. Solvent recovered from activated carbon in aqueous solution contained water. On decompressing the supercritical fluid being passed through a zeolite layer immediately after extraction, solvent having the same IR spectrum as the original solvent spectrum was recovered.
