title: 2D sandbox experiments of surfactant foams for mobility control and enhanced LNAPL recovery in layered soils.
abstract: The ability of surfactant foam to enhance mobility control and LNAPL recovery in a heterogeneous porous media was investigated through sandbox experiments with p-xylene used as LNAPL. A layered heterogeneous porous media was represented in a 2D sandbox filled with two layers of coarse and medium silica sand. Based on previous tests, the surfactant solution used was Ammonyx Lo at a concentration of 0.1% (w/w). The sandbox experimental program included tracer tests done under both uncontaminated and contaminated conditions, foam injection under uncontaminated conditions and surfactant solution and foam injection under contaminated conditions. Tracer tests indicated that the permeability contrast between sand layers was increased by LNAPL contamination. Foam injection under uncontaminated conditions presented a S-shaped front that indicated a better mobility control than the piston-shaped front obtained during tracer tests. During foam injection, complete sweep of the sandbox was achieved with 1.8pore volume (PV) compared to 2.8PV during tracer injection, thus indicating better mobility control with foam. Pre-flush of the contaminated sandbox with surfactant solution initiated p-xylene mobilization but no free phase was recovered at the effluent. A negligible p-xylene residual saturation was reached following foam injection in the contaminated sandbox. However, mass balance indicated a total recovery of only 48% of the initial p-xylene, thus indicating an underestimation of the recovery by volatilization. Recovery by volatilization was corrected, which gave the following proportions of LNAPL recovery mechanisms: 19% by mobilization, 16% by dissolution and 65% by volatilization. Results show the potential efficiency of foam remediation of LNAPL source zones in heterogeneous porous media. Still, further developments are needed prior to field scale application, which could benefit from in situ foam production that would simplify on-site operations.
authors.affiliation: Centre Eau Terre Environnement, Institut national de la recherche scientifique, 490 rue de la Couronne, Québec G1K 9A9, Québec, Canada.
authors.forename: Mélanie
authors.initials: M
authors.lastname: Longpré-Girard
authors.affiliation: Centre Eau Terre Environnement, Institut national de la recherche scientifique, 490 rue de la Couronne, Québec G1K 9A9, Québec, Canada. Electronic address: richard.martel@ete.inrs.ca.
authors.forename: Richard
authors.initials: R
authors.lastname: Martel
authors.affiliation: Centre Eau Terre Environnement, Institut national de la recherche scientifique, 490 rue de la Couronne, Québec G1K 9A9, Québec, Canada.
authors.forename: Thomas
authors.initials: T
authors.lastname: Robert
authors.affiliation: Centre Eau Terre Environnement, Institut national de la recherche scientifique, 490 rue de la Couronne, Québec G1K 9A9, Québec, Canada.
authors.forename: René
authors.initials: R
authors.lastname: Lefebvre
authors.affiliation: TechnoRem Inc., 4701 Rue Louis B Mayer, Laval H7P 6G5, Québec, Canada.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Lauzon
mesh_terms: D052918:Environmental Restoration and Remediation / Q000379:methods*; D016062:Porosity; D012822:Silicon Dioxide; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000737:chemistry*; D012996:Solutions; D013501:Surface-Active Agents / Q000737:chemistry*; D014992:Xylenes / Q000737:chemistry*
chemical_list: D012987:Soil; D012989:Soil Pollutants; D012996:Solutions; D013501:Surface-Active Agents; D014992:Xylenes; C031286:4-xylene; D012822:Silicon Dioxide
keywords: Foam; LNAPL recovery; Mobility control; Sandbox; Surfactant; p-Xylene