Density-modification displacement using colloidal biliquid aphron for entrapped DNAPL contaminated aquifer remediation

• Published in: Journal of hazardous materials 2022-06, Vol.432, p.128641-128641, Article 128641
• Main Authors: Yang, Chaoge, Liu, Fangyuan, Zhang, Chunpeng, Offiong, Nnanake-Abasi, Dong, Jun
• Format: Article
• Language: English
• Subjects: Colloidal biliquid aphrons; Density modification; Displacement; DNAPL; Groundwater; Phase behavior; Surface-Active Agents - analysis; Tetrachloroethylene - analysis; Water Pollutants, Chemical - analysis
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2022.128641

Colloidal biliquid aphron (CBLA) is a strong density modifier for dense nonaqueous phase liquids (DNAPLs). However, the underlying mechanisms responsible for density modification and displacement is not yet clear. Here, a series of batch column and sandbox experiments were conducted to achieve substantial removal and irreversible density reduction of tetrachloroethylene (PCE). The mass of PCE retained in the column and sandbox was less than 1% under suitable injection conditions, and the density of PCE in the effluent was less than that of water (fluctuated in the range of 0.74–0.96 g/cm3). The displacement process was controlled by the high viscosity ratio of CBLA to PCE (52.3). The emulsified and dissolved phase of PCE formed after reaction with CBLA, and the light nonaqueous phase liquid (LNAPL) phase formed after injecting demulsifier solution. The phase analysis played a significant role in monitoring the changes in concentration and density of PCE. The density-modification displacement technique using CBLA reduced the mass of residual PCE by a factor of 165 compared to surfactant flushing, and there was no risk of downward migration of PCE. This study contributes to a better remediation of entrapped DNAPL in contaminated aquifer. [Display omitted] •The mechanisms of density-modification displacement (DMD) using colloidal biliquid aphron (CBLA) was proposed.•Phase distribution played a significant role in density and concentration during DMD.•The displacement process was controlled by the high viscosity ratio of CBLA to contaminant.•No more than 1% of the tetrachloroethylene remain in the sandbox by using CBLA.•The density of tetrachloroethylene in the effluent was less than that of water by using CBLA.