Abstract: Traditional surfactant flushing technology has some disadvantages such as low elution efficiency, difficult control of liquid transport, and contaminated area extension. Colloidal gas aphrons (CGAs) can effectively avoid these problems with the characteristics of light density, small particle size, and good fluidity. Pressure can be used as a crucial parameter in the remediation process to efficiently reflect the CGAs migration distribution. One-dimensional and two-dimensional models were designed in this research to discuss the effects of medium grain size, moisture content, and polymer (xanthan gum) addition on the pressure of the system and the transport patterns of CGAs in soil. The results demonstrated that with the increase of the medium grain size, moisture content, and xanthan gum concentration, the pressure of the system decreased. Besides, the results of the CGAs injection into soil from a single point on one side of the simulated tank indicated that the migration traces in the medium was nearly semicircular and CGAs distributed uniformly in the coverage area, which effectively overcame the influence of gravity to its distribution in the medium. With the increase of medium grain size, the CGAs sweep efficiency increased first and then decreased. The maximum value of sweep efficiency reached 34.77% when the medium grain size was 0.8-1.0 mm. The moisture content augmentation of the medium also stimulated the increase of the sweep efficiency. Moreover, the addition of xanthan gum significantly improved the sweep efficiency of CGAs:when the mass concentration of xanthan gum was 500 mg/L, the sweep efficiency reached 40.28%,which is 1.48 times greater than that without xanthan gum addition.

Key words: colloidal gas aphrons, sweep efficiency, xanthan gum, pressure