Alcohol flushing for enhanced removal of coal tar from contaminated soils

Abstract

Alcohol flushing for enhancing the removal of coal tar from contaminated soils and reducing coal tar concentrations in the aqueous‐phase leachate was investigated. Four soil columns were packed with relatively undisturbed coal tar contaminated soils collected from a former coal gasification site. These columns were leached with water and then flushed with isopropyl alcohol (IPA) solutions. Initially, total coal tar concentrations in water leachate ranged from ∼0.1 to 150 mg/L for the four columns. Coal tar concentrations in the column effluent generally increased three to five orders of magnitude during the initial IPA flush. Each column was flushed with 1–3 pore volumes of an IPA solution. Reduction of coal tar concentrations in water leachate, attributed to the alcohol flushing, was noted in three of the four columns. The total coal tar removed from the soil columns during the IPA flushes constituted from 54 to 97% of the total coal tar removed during both water leaching (240–800 pore volumes) and alcohol flushing (1–3 pore volumes). The alcohol flushing removed from 3 to 19% of the total coal tar in the various soil columns. Results indicate that alcohol flushing can enhance the removal of coal tar from contaminated soils and can reduce the aqueous‐phase coal tar concentrations in leachate.