Anionic surfactant enhanced bacterial degradation of tributyltin in soil

The effect of an anionic surfactant, sodium dihexylsulfosuccinate (SDHS) addition on remediation of tributyltin (TBT) contaminated soil was investigated. Aerobic soil-slurry batch experiments were used to determine the adsorption, desorption, and bacterial degradation of TBT as well as its metabolites such as dibutyltin (DBT) and monobutyltin (MBT). The extent of butyltin adsorption over the concentration range of 1–100 mg Sn l−1 was in the order of MBT > DBT > TBT. The sub-critical micelle concentration (CMC) of SDHS (i.e., 10 mM) did not increase the amounts of desorbed TBT at the beginning of experiment, however, it enhanced the bacterial degradation of 100 mg Sn kg−1 TBT as seen from the increasing amounts of DBT and MBT in the liquid phase after 2 weeks. At the same time, the desorbed TBT was re-adsorbed to the soil in the experiment without SDHS. The complex of TBT and SDHS monomers was expected to enhance the interaction of TBT with indigenous soil bacteria. At supra-CMC SDHS (i.e., 70 mM), the desorbed TBT was not degraded because high concentrations of TBT and SDHS posed synergistic toxic effects to the bacteria. Consequently, the presence of anionic surfactant at sub-CMCs will be beneficial for the cleanup of TBT contaminated sites.

► Role of anionic surfactant (SDHS) on tributyltin (TBT) removal was elucidated. ► TBT and its metabolites acted like polar compounds in subsurface soil. ► Supra-CMC SDHS increased TBT desorption but prevented its degradation. ► Sub-CMC SDHS enhanced TBT degradation via complexation of TBT and SDHS monomers. ► Addition of sub-CMC SDHS is suggested for bioremediation of TBT contaminated soil.