Supercritical Fluid Extraction of Mixed Wastes: PAH, PCB, Uranium and Lanthanum in Solid Matrices

摘要

A sequential two-step supercritical fluid extraction technique has been developed for treating mixed wastes containing organic compounds (polychlorinated biphenyls and polyaromatic hydrocarbons) and metals (uranium and lanthanum). In the first step, the organic contaminants are extracted with neat supercritical fluid carbon dioxide at 250 atm and 150 ℃. The extraction efficiencies for the organic compounds are around 93-100%. In the second step, a TBP (tri-n-butylphosphate)-nitric acid ligand is added to the system to extract uranium and lanthanum from the solid at 75 ℃ and a supercritical fluid density of 0.77 g/mL. The extraction efficiency for uranium is over 90% and lanthanum around 80%. This sequential supercritical fluid extraction technique appears promising for large-scale treatment of mixed wastes.