Mechanisms of irreversible density modification using colloidal biliquid aphron for dense nonaqueous phase liquids in contaminated aquifer remediation

• Published in: Journal of hazardous materials 2021-08, Vol.415, p.125667-125667, Article 125667
• Main Authors: Yang, Chaoge, Offiong, Nnanake-Abasi, Zhang, Chunpeng, Liu, Fangyuan, Dong, Jun
• Format: Article
• Language: English
• Subjects: aquifers; carbon tetrachloride; Co-existing ions; Colloidal biliquid aphrons; Density modification; DNAPL; groundwater contamination; Kinetic model; liquids; methylene chloride; nitrobenzenes; remediation; response surface methodology; temperature; tetrachloroethylene; trichloroethylene
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2021.125667

The use of colloidal biliquid aphron (CBLA) as density modifier to reduce the density of dense nonaqueous phase liquids (DNAPLs) irreversibly is an efficient strategy to control the migration of DNAPLs in contaminated aquifers. However, the process and mechanism of the density regulation using CBLA is still not clear and there is still a big gap in the application of CBLA in actual contaminated sites. In this study, we carried out density modification of 5 DNAPLs (nitrobenzene (NB), dichloromethane (DCM), trichloroethylene (TCE), carbon tetrachloride (CTC), perchloroethylene (PCE)) using CBLA and studied the effect of co-existing ions by 3D response surface method. We found that DNAPLs changed to light nonaqueous phase liquids (LNAPLs) and float up after interaction with light organic liquid from CBLA. The density modification process is limited by the demulsificaiton of CBLA and the density of DNAPL itself. Density regulation of DNAPLs followed pseudo-second-order kinetics. The co-existing ions affected the stability of CBLA and the demulsification ability of the demulsifier. Aquifer materials and low temperature did not influence the density control effect of CBLA. This research advances the practical application of density control of DNAPLs using CBLA, and makes important contributions for subsequent combined remediation approach. [Display omitted] •Colloidal biliquid aphron (CBLA) is only suitable for density control of miscible dense nonaqueous phase liquids (DNAPLs).•The density modification process is limited by the demulsificaiton of CBLA and the density of DNAPL itself.•Density regulation process of DNAPLs follows pseudo-second-order kinetics model.•CBLA can still adjust the density of different pollutants less than 0.986 g/cm3 at 10 ℃.•The order of the degree of co-existing ions effect on the density regulation is as follows: CaCl2 > NaHCO3 > KCl > Na2SO4.