Removal of Nonvolatile Hydrophobic Compounds from Artificially and Naturally Contaminated Soils by Column Flotation

Abstract

Removal of a nonvolatile paraffin oil from spiked soils using column flotation with countercurrent bubbles was explored at both ambient and elevated temperatures. Up to 80% of the contaminant was separated from the coarse fraction (250 to 800 µm) by flotation at 45°C using aqueous solutions of anionic and nonionic surfactants or alkali salt as collectors. With the 75 to 800 µm fraction, removal efficiencies of up to 65% was achieved. Sodium dodecyl-sulfate and Triton 100X at 50 ppm concentrations as well as sodium carbonate at pH 10 were found to yield similar removal efficiencies. Same surfactants were tested in soil washing experiments at similar and higher dosages. Removal efficiency by flotation was higher than those obtained by soil washing in all cases. In addition, as high surfactant dosage are not used in flotation, unlike in the case of soil washing, the problem of formation of stable emulsions was absent. Experiments with soil polluted by hydrocarbons from a contaminated site demonstrated the fe...