Enhanced In Site Extraction of Heavy Metals Using Surfactant Foams

The Phase I objective is to assess the use of surfactant colloidal gas aphron (CGA) foams for remediation of heavy metals in contaminated aquifers. One of the most important factors limiting pump-and-treat methods for metal as well as organic pollutant remediation is poor transport of extraction solutions from injection sites to zones of contamination because of movement through preferential flow paths. Surfactant foams may be an ideal medium to improve the transport of metal extracting agents in the subsurface because foams move through aquifer sediments in a "plug flow" manner (i.e., entering small micropores as well as preferential flow paths). The use of foams for the solubilization, mobilization, and recovery of metals (lead and mercury) will be investigated. Surfactant foams will be generated in a spinning-disc foam generator from dilute ( 0.1%) anionic, cationic, and nonionic surfactant solutions. Envirogen, Inc., will examine the potential for using surfactant CGA foams in conjunction with metal chelators and acid solutions to enhance the extraction of lead or mercury in model aquifer systems comprised of silica sand or a defined aquifer sediment spiked with a known amount of metal. Results will be compared to control columns flushed with artificial groundwater. In Phase II, work will be expanded to pilot-scale testing to investigate foam flow and mobilization of various heavy metals in heterogeneous aquifer sediments of varying permeabilities. The results from these studies will provide valuable information on the uses of surfactant foams for remediation of metal-contaminated sediments. The final goal of the Phase I and Phase II projects is to commercialize a new technology to mobilize heavy metals and radionuclides in subsurfaces using foams as a delivery vehicle for chemicals capable of extracting metals. Envirogen, Inc., knows of no previous work assessing the potential use of surfactant foams for in situ mobilization of heavy metals; thus, this project represents a completely new approach to metals remediation.