Surfactant Enhancements

Surfactant enhancement is a technology used to remove contaminants from soils and water at hazardous waste sites. The application of surfactants enhances remediation by (a) increasing contaminant mobility and solubility, (b) decreasing the mobility of contaminants, and (c) increasing the rate of biodegradion of contaminants in soil. 

Surfactants increase the apparent solubility of the contaminant in water and thus water becomes more effective in the removal of nonaqueous phase liquids (NAPLS). Surfactants also reduce the interfacial tension between the water and the NAPL, thus NAPL mobility increases. However, cationic surfactants increase the capacity of soil to sorb hydrophobic organic chemicals such as polyaromatic hydrocarbons (PAHs). 

The application of this technology involves the construction of two wells. One well serves to introduce the surfactant to the dense NAPL (DNAPL), while the second serves as a means to extract the polluted liquid (Fig. 14.2). 

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Microemulsions became well known from about 1975 to 1980 because of their use ia "micellar-polymer" enhanced oil recovery (EOR) (35). This technology exploits the ultralow iaterfacial tensions that exist among top, microemulsion, and bottom phases to remove large amounts of petroleum from porous rocks, that would be unrecoverable by conventional technologies (36,37). Siace about 1990, iaterest ia the use of this property of microemulsions has shifted to the recovery of chloriaated compounds and other iadustrial solveats from shallow aquifers. The latter appHcatioa (15) is sometimes called surfactant-enhanced aquifer remediation (SEAR). 

The focus of more recent work has been the use of relatively low concentrations of additives in other oil recovery processes. Of particular interest is the use of surfactants (qv) as CO2 (4) and steam mobiUty control agents (foam). Combinations of older EOR processes such as surfactant-enhanced alkaline flooding and alkaline—surfactant—polymer flooding show promise of improved cost effectiveness. 

Including a surfactant in the caustic formulation (surfactant-enhanced alkaline flooding) can increase optimal salinity of a saline alkaline formulation. This can reduce iaterfacial tension and increase oil recovery (255,257,258). Encouraging field test results have been reported (259). Both nonionic and anionic surfactants have been evaluated in this appHcation (260,261). 

Surfactants evaluated in surfactant-enhanced alkaline flooding include internal olefin sulfonates (259,261), linear alkyl xylene sulfonates (262), petroleum sulfonates (262), alcohol ethoxysulfates (258,261,263), and alcohol ethoxylates/anionic surfactants (257). Water-thickening polymers, either xanthan or polyacrylamide, can reduce injected fluid mobiHty in alkaline flooding (264) and surfactant-enhanced alkaline flooding (259,263). The combined use of alkah, surfactant, and water-thickening polymer has been termed the alkaH—surfactant—polymer (ASP) process. Cross-linked polymers have been used to increase volumetric sweep efficiency of surfactant—polymer—alkaline agent formulations (265). 

Pigment Dispersion. AMP is used widely as a pigment dispersant for water-based paints and paper coatings. In small amounts, it efficiently disperses pigments and improves pH stabiUty, viscosity, corrosion inhibition, and odor (13). When AMP is used in conjunction with other surfactants, enhanced performance is obtained with less of these ingredients in the dispersion. 

Emission spectra Phosphorescence Differential phase Surfactant enhancement (micelles, etc.)... 

Toxicity as a result of the surfactant-enhanced PAH concentration in the aqueous phase... 

Boonchan S, ML Britz, GA Stanley (1998) Surfactant-enhanced biodegradation of high molecular weight polycyclic aromatic hydrocarbons by Stenotrophomonas maltophilia. Biotechnol Bioeng 59 480-494. 

Tiehm A, M Stieber, P Werner, FM Frimmel (1997) Surfactant-enhanced mobilization and biodegradation of polycyclic aromatic hydrocarbons in manufactured gas plant soil. Environ Sci Technol 31 2570-2576. 

Walter MV, EC Neilson, G Eirmstone, DG Martin, Ml Clayton, S Simpson, S Spaulding (1997) Surfactant enhances biodegradation of hydrocarbons microcosm and field study. J Soil Contam 6 61-77. 

Sahoo D, JA Smith, TE Imbrigiotta, HM Mclallan (1998) Surfactant-enhanced remediation of a trichloroeth-ene-contaminated aquifer. 2. Transport of TCE. Environ Sci Technol 32 1686-1693. 

In buffered surfactant-enhanced alkaline flooding, it was found that the minimum in interfacial tension and the region of spontaneous emulsification correspond to a particular pH range, so by buffering the aqueous pH against changes in alkali concentration, a low interfacial tension can be maintained when the amount of alkali decreases because of acids, rock consumption, and dispersion [1826]. 

T. R. French and C. B. Josephson. Surfactant-enhanced alkaline flooding with weak alkalis. US DOE Rep NlPER-507, NIPER, February 1991. 

Boopathy, R. and Manning, J., Surfactant-enhanced bioremediation of soil contaminated with 2,4,6-trinitrotoluene in soil slurry reactors, Water Environ. Res., 71, 119-124, 1999. 

The basic mechanism for surfactants to enhance solubility and dissolution is the ability of surface-active molecules to aggregate and form micelles [35], While the mathematical models used to describe surfactant-enhanced dissolution may differ, they all incorporate micellar transport. The basic assumption underlying micelle-facilitated transport is that no enhanced dissolution takes place below the critical micelle concentration of the surfactant solution. This assumption is debatable, since surfactant molecules below the critical micelle concentration may improve the wetting of solids by reducing the surface energy. 

Both nonionic and anionic surfactants have been evaluated in this application (488,489) including internal olefin sulfonates (487, 490), linear alkylxylene sulfonates (490), petroleum sulfonates (491), alcohol ethoxysulfates (487,489,492). Ethoxylated alcohols have been added to some anionic surfactant formulations to improve interfacial properties (486). The use of water thickening polymers, either xanthan or polyacrylamide to reduce injected fluid mobility mobility has been proposed for both alkaline flooding (493) and surfactant enhanced alkaline flooding (492). Crosslinked polymers have been used to increase volumetric sweep efficiency of surfactant - polymer - alkaline agent formulations (493). 

Surface wave, 17 422. See also S-wave Surfactant adsorption, 24 119, 133-144 at the air/liquid and liquid/liquid interfaces, 24 133-138 approaches for treating, 24 134 measurement of, 24 139 at the solid/liquid interface, 24 138-144 Surfactant blends, in oil displacement efficiency, 13 628-629 Surfactant-defoamers surface tension, <5 244t Surfactant-enhanced alkaline flooding,... 

Mulligan CN, Youg RN, Gibbs BF. Surfactant-enhanced remediation of contaminated soil a review. Eng. Geol. 2001 60 371-382. 

Schroth, M. H., 1998, Field Method for the Feasibility Assessment of Surfactant-Enhanced DNAPL Remediation In Nonaqueous-Phase Liquids — Remediation of Chlorinated and Recalcitrant Compounds (edited by G. B. Wickramanayake and R. E. Hinchee), Battelle Press, Columbus, OH, pp. 199-200. 

The CESAR (chemically enhanced solubilization for aquifer remediation) technology is a surfactant-enhanced pump-and-treat technology that remediates an aquifer by treating organic contaminants with a chemical surfactant solution. The surfactant solubilizes the contaminants, thus making them more readily transportable to the extraction weUs. This technology is currently commercially available. 

Liu Q, Dong M, Ma S, Tu Y (2007) Surfactant enhanced alkaline flooding for western canadan heavy oil recovery. Colloids Surf A 293 63-71... 

Stoebe T, Lin Z, Hill RM, Ward MD, Davis HT (1997) Superspreading of aqueous films containing trisiloxane surfactant on mineral oil. Langmuir 13 7282-7286 Stoebe T, Hill RM, Ward MD, Scriven LE, Davis HT (1996) Surfactant-enhanced spreading. Langmuir 12 337-344... 

Effective use of inoculants and surfactants Enhanced mass transfer costs ... 

Abdul, A. S. Gibson, T. L. (1991). Laboratory studies of surfactant-enhanced washing of polychlorinated biphenyl from sandy material. Environmental Science Technology, 25(4), 665-71. 

Miller, R.M. (1995b). Surfactant-enhanced bioavailability of slightly soluble organic compounds. In Bioremediation-Science Applications, ed. H. Skipper, pp. 35-54. Madison, WI Soil Society of America. 

Penetration enhancers have been used to facilitate the absorption of higher molecular weight molecules. The mode of action of the surfactant enhancers is often attributed to membrane damage [37]. However, studies in epithelial cell monolayers suggest that some surfactant-based absorption enhancers act primarily by increasing the permeability of tight junctions [38]. Nevertheless, except for the chelators and nonsurfactants, which exert their... 

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