Basis for formulating biosurfactant mixtures to achieve ultra low interfacial tension values against hydrocarbons

Abstract

Biosurfactants could potentially replace or be used in conjunction with synthetic surfactants to provide for more cost-effective subsurface remediation. The design of surfactant formulations that are effective in lowering interfacial tension (IFT), which is necessary to mobilize entrapped hydrocarbons, requires information about the surface-active agent (surfactant) and the targeted non-aqueous phase liquids (NAPL). We hypothesized that biosurfactant and synthetic surfactant mixtures can be formulated to provide the appropriate hydrophobic/hydrophilic conditions necessary to produce low IFT against NAPLs, and that such mixtures will produce synergism that make them more effective than individual biosurfactants or synthetic surfactants. Our work tested the interfacial activity of biosurfactants from individual strains and mixtures of biosurfactants from different strains with and without a synthetic surfactant. Multiple regression analysis showed that, for lipopeptide biosurfactants produced by various Bacillus species, the interfacial activity against toluene depended on the relative proportions of 3-OH-C14, C15, C16, and C18 in the fatty acid tail. As the fatty acid composition became more heterogeneous the system produced lower IFT against toluene. In mixtures of lipopeptide biosurfactants with the more hydrophilic, rhamnolipid biosurfactant, the IFT against toluene decreased as the percentage of the 3-OH C14 fatty acid increased in the lipopeptide. Mixtures of lipopeptide biosurfactants with the more hydrophobic synthetic surfactant, C12, C13-8PO SO4Na, were able to produce low IFT against hexane and decane. In general, we found that lipopeptide biosurfactants with a heterogeneous fatty acid composition or mixtures of lipopeptide and rhamnolipid biosurfactants lowered the IFT against hydrophilic NAPLs. Conversely, mixtures of lipopeptide biosurfactants with a more hydrophobic synthetic surfactant lowered the IFT against hydrophobic NAPLs.

Estimating Factors Determining Emulsification Capability of Surfactant-Like Peptide with Coarse-Grained Molecular Dynamics Simulation

“…Furthermore, it also reported that lipopeptide biosurfactant could be produced by bacteria in an oil reservoir [9]. Nutrition supplementation could increase the in-situ production of lipopeptide biosurfactant in oil reservoirs [10].…”

Use of Biosurfactants in Oil Recovery

“…CMC is the concentration at which the biosurfactants form micelles and is the minimum concentration needed to mobilize entrapped oil (Youssef et al 2009;Sen 2010). Many synthetic surfactants have higher CMC (>100 mg/L) than biosurfactants (Youssef et al 2007a). Thus, low biosurfactant concentrations can be effective in mobilizing entrapped oil.…”

“…To our knowledge, there are still not any reports of ex situ field trial applications of biosurfactants. A promising approach is the use biosurfactants in conjunction with synthetic surfactants to reduce the amount of synthetic surfactants needed, providing cost savings (Youssef et al 2007a;Al-Sulaimani et al 2012).…”

Pore-Scale Mechanisms of the Synergistic Effects between Microbial Cultures and Chemical Surfactants on Oil Recovery

“…It is generally believed that the main synergistic mechanism for the EOR of biosurfactants and chemical surfactants is by reducing the oil/water IFT and by altering the wettability. , Al-Wahaibi et al suggested that the mixture could improve the macroscale sweep efficiency by IFT reduction while improving the microscale washing efficiency after hot water injection by reducing the viscosity . Youssef et al found that mixtures with different biosurfactants and chemical surfactants could achieve an ultra-low IFT by changing the fatty acid composition of the biosurfactant. , Mędrzycka et al suggested that a mixture of a biosurfactant and a surfactant can reduce the critical micelle concentration (cmc), which reduces the cost of surfactant flooding…”

“…13 Youssef et al found that mixtures with different biosurfactants and chemical surfactants could achieve an ultra-low IFT by changing the fatty acid composition of the biosurfactant. 21,22 Medrzycka et al suggested that a mixture of a biosurfactant and a surfactant can reduce the critical micelle concentration (cmc), which reduces the cost of surfactant flooding. 23 With regard to the mechanism of wettability alteration, a wetting test using a synthetic base oil indicated that the wettability was more efficiently altered by a mixture of a nonionic surfactant (NS) (ROKAnol NL6) and a biosurfactant (rhamnolipid JBR 425) than by either single component.…”