CREOSOTE LEACHING FROM A CONTAMINATED SATURATED SAND COLUMN

The leaching of six aromatic compounds from creosote contaminated sand was studied in a laboratory column experiment for a period of 36 days. The compounds studied were benzene, toluene, o-xylene, phenol, o-cresol and naphthalene. They accounted for 21.8% (wt/wt) of the creosote. Phenol and o-cresol were totally leached from the creosote contaminated sand within the first 5 days. The maximum concentration observed in the column was 174 mg l-1 for phenol and 46 mg l-1 for o-cresol. Benzene was leached within 10 days (max. concentration 63 mg l-1). The concentration of these three compounds was lower than predicted from Raoult's law, indicating that equilibrium between water and creosote was not reached. Toluene was leached after 36 days with a maximum concentration of 51 mg l-1. o-xylene and naphthalene were not totally leached out when the experiment ended, and at that time the concentration was 40 mg l-1 for o-xylene and 12.5 mg l-1 for naphthalene. The naphthalene concentration was expected from Raoult's law, but the o-xylene concentration was surprisingly high. The reason for this was not identified. It is shown that the mole-fraction in Raoult's law in many cases can be approximated by the weight-fraction. The underestimation for the predicted aqueous concentration caused by this approximation is not greater than a factor of three depending on the composition of the creosote and the component investigated.