Influence of biofilm on the transport of fullerene (C60) nanoparticles in porous media

The significance of biofilm on fullerene C₆₀ nanoparticles transport and deposition were examined both in porous media and quartz crystal microbalance with dissipation (QCM-D) systems under a variety of environmentally relevant ionic strength (1-25 mM in NaCl and 0.1-5 mM in CaCl₂) and flow conditions (4-8 m day⁻¹). The magnitudes of deposition rate coefficients (k_d) were compared between porous media with and without biofilm extracellular polymeric substances (EPS) coating under equivalent fluid velocities and solution chemistries. The observed k_d were greater in porous media with biofilm EPS coating relative to those without biofilm EPS coating across the entire solution ionic strengths and fluid velocities examined, demonstrating that the enhancement of C₆₀ deposition by the biofilm EPS coating is relevant to a wide range of environmental conditions. This greater deposition was also observed on silica surfaces with biofilm EPS coating in QCM-D system. The results clearly showed that biofilm EPS have a great influence on C₆₀ deposition. Derjaguin-Landau-Verwey-Overbeek (DLVO) theory could not explain the enhanced C₆₀ deposition by biofilm EPS. Biochemical and physical characteristics of biofilm EPS were responsible for the increased C₆₀ deposition.