The Fate And One Dimensional Transport Of Creighton Colloidal Silver Nanoparticles Through Saturated Porous Media

With the ubiquitous burst of nanotechnology, silver nanoparticles (AgNPs) have become indispensable in numerous industrial, medicinal, and research applications. Consequently, AgNPs have been alarmingly disposed into subsurface water increasing the risk of human and environmental exposure. While mechanisms of AgNP cytotoxicity have been reported, research studies on AgNP transport in subsurface water are needed, according to U.S. Environmental Protection Agency (EPA). The main goal of this study was to investigate the environmental fate and transport of widely-used Creighton colloidal AgNPs in a laboratory transport system simulating a porous, saturated groundwater aquifer. To achieve this, a large volume of AgNPs was synthesized, characterized using a suite of well-established analytical and microscopy techniques, and manipulated by tangential flow filtration. AgNPs and a conservative tracer, Cl- as a potassium chloride solution, were pulse-injected upward through a one-dimensional laboratory column (5 cm in depth, 2.5 cm diameter) at fixed pH, flow rate, and ionic strength, and pore volume. Breakthrough curves for AgNP transport were constructed using UV-Vis absorption, flame atomic absorption spectroscopy (FAAS) and inductively coupled plasma optical emission spectroscopy (ICP-OES). Smaller AgNPs (1-20 nm in diameter) were found to elute faster than larger AgNPs (1-100 nm in diameter). Flow rate and AgNP size were found to influence the sorption of AgNPs onto the media, as evidenced by the size and shape of the non-equilibrium breakthrough curves. Facilitated transport was attributed to moderate electrostatic repulsions between the negatively charged AgNPs and the polar glass beads. The transport of the AgNPs through the one dimensional laboratory system and the accurate ICP-OES-based quantification of nanosilver concentration in colloidal samples were translated into two novel laboratory experiment modules, which were successfully implemented into the Experimental Nanomaterials and Nanoscience course and the Instrumental Analysis laboratory course at WSU respectively.