Enhanced Delivery of Nanoscale Zero-Valent Iron in Porous Media by Sodium Dodecyl Sulfate Solution and Foam

摘要

The feasibility of using sodium dodecyl sulfate (SDS) foam and solution to deliver nanoscale zero-valent iron (nZVI) in unsaturated porous media was investigated. Three main results were found. First, batch experiments showed that the foam quality and capability to carry nZVI improved with increased agitator stirring speed. However, the distribution of nZVI in foams gradually became nonuniform with increased nZVI concentration. Presence of nZVI did not reduce foam stability. Second, column experiments revealed that fractions of injected nZVI exiting the column for SDS-nZVI suspension and nZVI-laden foams were higher than that for bare nZVI suspension. Thus, the SDS solution and foams were promising vehicles for nZVI delivery. Finally, tank experiments were conducted to study the migration and distribution characteristics of nZVI carried by the three vehicles. Compared with those of bare nZVI suspension, influence regions of nZVI in porous media for SDS-nZVI suspension and nZVI-laden foams were significantly improved. Further study showed that foam delivery dramatically increased the lateral delivery distance and distribution homogeneity of injected nZVI particles compared with the vehicle of SDS solution. Therefore, migration of nZVI in porous media was greatly facilitated by the vehicle of SDS foams. This research not only focuses on the nZVI delivery in one-dimensional scale but also gives a comprehensive analysis on the spatial distribution of nZVI carried by three vehicles, especially on the feature of the distribution homogeneity and lateral migration, which were not extensively studied before. Results from this study can provide a theoretical support for the technical installation and operation of foam-assisted transport of amendment in soil remediation.