Creosote leaching from a contaminated saturated sand column

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Abstract
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 1‐1 for phenol and 46 mg l‐1 for o‐cresol. Benzene was leached within 10 days (max. concentration 63 mg 1‐1). 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 1‐1. o‐xylene and naphthalene were not totally leached out when the experiment ended, and at that time the concentration was 40 mg 1‐1 for o‐xylene and 12.5 mg 1‐1 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.