Comparison of the fixed-bed and batch leaching characteristics of aromatic compounds in residually trapped crude oils and oily wastes

Abstract

The fixed-bed dissolution characteristics were characterized for five aromatic components in two crude oils residually trapped in glass beads and two refinery residuals containing an oily phase. Good agreement between predicted and experimental results for the fixed-bed dissolution of benzene, toluene, ethylbenzene, p- and m-xylenes, and naphthalene (BTEXN) from the two crude oils was observed over a wide range (three to four orders of magnitude) in aqueous effluent concentrations. The partition coefficients used to describe the experimental leaching curves agreed well with those independently measured from multiple-batch aqueous extractions. For the two refinery residuals, good agreement between predicted and experimental fixed-bed dissolution was also observed for a one- to two-orders of magnitude range in leachate concentrations. These results illustrate a methodology for predicting time-dependent leaching behavior for an oily residual using partition coefficients measured from batch leaching tests. In addition, it was found that when the oil content of the oily residuals was accounted for, the partition coefficients measured for BTEXN for the oily residuals were similar to those for the crude oils. In the absence of batch measurements for a given oily residual, this latter result suggests that the time-dependent leaching behavior, under local equilibrium conditions, can be estimated from measurements of only the contaminant concentrations in the waste and the oil content.