Effect of combined Bacillus subtilis on the sorption of phenanthrene and 1,2,3-trichlorobenzene onto mineral surfaces
Received for publication March 25, 2009. In the natural environment, minerals are often associated with coexisting microorganisms. These interactions have profound impacts on the fate of a wide variety of contaminants. However, little information is available on the sorption of hydrophobic organic compounds (HOC), such as polycyclic aromatic hydrocarbons and chlorinated benzenes, onto the composites of minerals with bacteria, and knowledge of the influence of combined bacteria on HOC sorption to minerals is limited. In our study, sorption isotherms of phenanthrene (Phen) and 1,2,3-trichlorobenzene (TCB) onto Bacillus subtilis, minerals (kaolinite, montmorillonite, and goethite), and mineral–B. subtilis composites were studied to determine the role of B. subtilis in sorption. For pure mineral systems, the order of Phen and TCB sorption affinity was montmorillonite > kaolinite > goethite. For mineral–B. subtilis composites, the trend was montmorillonite > goethite > kaolinite, consistent with that of their ability to combine with bacteria. The coating of B. subtilis with minerals enhanced the sorption due to the strong sorption of Phen and TCB onto B. subtilis cells and the increase of total organic carbon of minerals. With increasing B. subtilis concentration, sorption of Phen and TCB on pure B. subtilis cells decreased, but sorption on kaolinite surface increased. Sodium azide can greatly reduce sorption capacity but increases sorption linearity for B. subtilis and mineral–B. subtilis composites. Compared with TCB, Phen had higher sorption affinity due to its high hydrophobicity. Our results may be useful for understanding the role of bacteria in regulating the distribution and transport of HOCs in the environment.