Economic in situ soil flushing using common surfactants may be a good substitute for exhaustive, pressurized soil washing or bioremediation requiring high energy consumption or laborious technique. Two model surfactants, sodium dodecyl sulfate (SDS) and polyoxyethylene (20) sorbitan monooleate (Tween-80), were chosen as flushing agents. Those surfactant solutions were applied to clean hydrocarbon (motor oil) contaminated sand soil. A kinetic investigation such as order of reaction of pollutant compounds, flushing mode (semi-continuous and continuous), change of soil pore matrix, etc. comprised a main part of this work. We found that the hydrocarbon elution curves were dropping in an exponential way, which was stiffer with higher surfactant concentrations. Higher surfactant concentration, higher flow rate, and lower porosity guaranteed higher removal efficiency as well as higher removal rate. Strong initial lag phases were found for Tween-80 solutions. A modified Monod-type reaction model describing the removal kinetics was proposed to be the first-order reaction, which agreed well with most of the experimental results. The curve-fitted parameters, n, k0 and K1 were linear functions of surfactant concentration and reciprocal of soil porosity.

Kinetics in-situ Soil Washing Hydrocarbon Oil Surfactant

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