Influencing factors on the stabilization of colloid biliquid aphrons and its effectiveness used for density modification of DNAPLs in subsurface environment

4-Aquifer contamination caused by non-aqueous phase liquids (NAPLs) is a serious environmental problem worldwide, especially dense nonaqueous phase liquids (DNAPLs). They could quickly deposited as an impermeable layer at the bottom of aquifer because of their low solubility and high density. NAPLs contaminated zones can serve as a persistent source of groundwater pollution, and pose a serious threat to human health and ecosystems. Density modification displacement (DMD) is a promising approach to prevent DNAPLs downward migration during surfactant-based remediation process. In this work, colloid biliquid aphrons (CBLA) was prepared and characterized; the influencing factors on CBLA stabilization were investigated, and the effectiveness of CBLA used for DNAPLs density modification in groundwater was evaluated. The results indicated that the optimum preparation phase volume ratio (PVR) of CBLA was 8; the particle size of CBLA decreased drastically while PVR ranged from 2 to 8; the.-potential of CBLA was negative and had a positive relationship with PVR. CBLA solution had shear thinning properties, and the relationship between shear stress and shear rate belongs to Herschel-Bulkley model; sulfate ion showed stronger destructive ability on CBLA compared with chloride ion. Moreover, the optimum ratio of CBLA to trichloroethylene (TCE) for density modification was 9/5, and the density of TCE could be changed from 1.464 g/cm(3) to 0.980 g/cm(3). Therefore, CBLA could transform DNAPL to LNAPL successfully, and it had promising potential for DNAPL polluted groundwater remediation.