Biosurfactant Solubilization of PAHS
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A biosurfactant produced by Rhodococcus strain H13-A and a commonly used synthetic surfactant, Tween-80 (polyoxyethylene sorbitan monooleate), are compared for their effectiveness in enhancing the aqueous concentrations of polycyclic aromatic hydrocarbons (PAHs) from a complex organic phase (crude oil). The focus of this research is on the highly toxic and regulated constituents of weathered crude oil, namely the three- and four-ring aromatics and the methyl-substituted derivatives. The micellar-enhanced 'solubility' was monitored in the presence of surfactants when compared to solubility in the absence of surfactants. The phenanthrenes, fluorenes, pyrenes, and chrysenes showed statistically significant increases in their aqueous-plus-micellar-phase concentrations in the presence of surfactants compared to the controls. Moreover, the enhanced PAH concentrations ranged from 2.2 times to more than 35 times for the biosurfactant treatment compared to the synthetic surfactant treatment. In the biosurfactant treatment, the enhancement in 'solubility' was also higher for the methyl-substituted aromatics when compared to their parent compounds, although these substituted compounds are naturally less soluble than the parent. The biological surfactant was, therefore, more effective than its synthetic counterpart in solubilizing these compounds from a complex mixture to an aqueous solution.