Transport of Engineered Nanomaterials in Porous Media: Groundwater Remediation Application and Effects of Particle Shape

Nanotechnology, referring to any science which utilizes particles at the nanoscale, has substantially grown in recent years for its wide spectrum of potential uses. Many theories and models have been developed around the transport of spherical particles; however nanoparticles can be found in various shapes which could greatly affect the predicted transport and retention in the subsurface. This research explores the beneficial use of carbon nano-onions (CNOs) for environmental remediation and investigates the transport of CNOs in saturated porous media. Surface oxidized CNOs possessed 10 times higher sorption capacity compared to C60 for heavy metal ions including Pb2+, Cu2+, Cd2+, Ni2+, and Zn2+. CNOs aqueous suspension can be very stable in NaCl solution at ionic strength up to 30 mM and CaCl2 solution up to 4 mM CaCl2 when pH ranged from 5 to 9, consistent with environmental relevant conditions. Interactions of CNOs with iron oxide and silica surfaces under favorable condition were found to be electrostatic in origin. Mobility of CNOs in quartz sands was controlled by electrolyte type and concentration. Approximately 4.4%, 25.1%, and 92.5% of injected CNO mass were retained in the sand column in ultrapure water, 1 mM NaCl, and 1 mM CaCl2 solutions, respectively. The second part of this research explored the influence of nanoparticle shape on the transport and retention. Spherical polystyrene nanoparticles were stretched into rod shapes with either 2:1 or 4:1 aspect ratio. Using Quartz Crystal Microbalance with Dissipation (QCM-D) particle deposition experiments, spherical particles displayed a higher deposition rate compared to rod-shape under favorable conditions. The rod-shape particles were all insensitive to changes in ionic strengths of 10 to 100 mM NaCl. Transport and deposition in saturated porous media was investigated by microfluidic flow cell experiments incorporated with Laser Scanning Cytometry (LSC). Results showed higher attachment rate for rod-shape particles compared to spherical. It was also determined that physical and chemical surface heterogeneity plays a significant role in the observed attachment onto the glass beads. Advisor: Yusong L