MSc Thesis Title: Influence of graphene oxide nanoparticles on the co-transport of model bacteria in saturated porous media

Tuesday 4 December 2018, at:13:00, Venue: Hall K2.A11

Examination Committee

• Professor Constantinos Chrysikopoulos (advisor)
• Associate Professor Danae Venieri
• Professor Ioannis Tsanis

Abstract:

Graphene oxide (GO) is a material with rapid production growth and wide range of applications, consequently engineered GO nanoparticles may enter subsurface formations, where biocolloids of human origin are in abundance. This master thesis examines the effect of engineered GO nanoparticles on the transport and co-transport of three common bacteria (i.e., Escherichia coli, Enterococcus faecalis, and Staphylococcus aureus) of human origin in saturated porous media. Initially, flowthrough experiments were conducted in water-saturated columns, packed with coarse quartz sand, in order to determine the transport characteristics of GO and each individual bacterium separately. Subsequently, changes in motility and/or column retention of each pathogenic microorganism were investigated under simultaneous pumping of GO suspension. Additionally, co-transport experiments of the bacteria were performed in the presence and absence of GO suspension, in order to investigate any changes in bacterial transport that may be caused by the interaction (e.g., synergistic or non-action) of the three examined bacteria. All experiments were conducted under the same aqueous chemistry conditions (pH = 4, IS = 2 mM) and at a constant ambient temperature of 25℃, with an initial concentration of ~105 CFU/mL and 20 mg/L for the biocolloids and the graphene oxide suspension, respectively.

Mathematical modeling of the experimental transport data was performed with the ColloidFit fitting software and appropriate breakthrough curves were constructed to describe the transport and co-transport experiments. Mass recovery and temporal moment calculations were also performed. The differences in the recovered mass of the bacteria breakthrough curves in the presence and absence of GO suspension were used for evaluation of the influence of GO nanoparticles on the transport behavior of bacteria, as well as for indirect evaluation of the potential inactivation capacity and potential anti-bacterial action of GO. In addition, collision efficiencies were calculated using the classical filtering theory (CFT). Finally, the interaction energy profiles between GO-bacteria, GO-quartz sand, bacteria-quartz sand, bacterium-bacterium were constructed for the given experimental conditions by applying the classical DLVO and XDLVO theories, using the measured values ​​of hydrodynamic diameter, and z-potential values of bacteria, GO and coarse quartz sand.