Supercritical carbon dioxide extraction of chlorinated aromatics from DOE job control wastes

As a promising decontamination technology, a supercritical CO2 extraction process was investigated for removing and recovering polychlorinated biphenyls (PCBs) from DOE contaminated Job Control Wastes (JCW). The experimental and process design of this process was conducted in two stages. First, the feasibility of using supercritical CO2 to remove PCBs from JCW was tested in an analytical-scale apparatus. In this stage, 1,2,4-trichlorobenzene (TCB) was chosen as the surrogate for PCBs, and the recovery of TCB approached 100% at optimal condition. Second, a bench-scale apparatus was employed for process development testing. Extraction temperatures, pressures, and extraction time were varied to identify favorable operating conditions, and the effects of cosolvent and extraction time on supercritical extraction of PCBs were also investigated. The experimental results demonstrate the potential of using supercritical CO2 extraction as a PCB extraction technology for DOE JCW.;A model based on regular solution theory was developed to correlate solid solubilities in pure or cosolvent modified supercritical CO2. Two interaction parameters, the carbon dioxide-solute interaction parameter beta 12 and the solute-cosolvent interaction parameter beta23, are employed in this model to represent the intermolecular forces between solute, solvent, and cosolvent. The dependence of these two interaction parameters on solvent solubility parameter, solute properties, and temperature were investigated, and the dependence of beta23 on cosolvent properties was also studied. Experimental data from a variety of nonpolar, polar, and hydrogen bonding solids and several cosolvents were used to evaluate the model. The correlation results are satisfactory for all of the binary and ternary systems.