This NSF award by the Environmental Health and Safety of Nanotechnology program supports work by Professor Eugene J. LeBoeuf at Vanderbilt University, and Professors Yusong Li and Yongfeng Lu at the University of Nebraska , Lincoln to investigate the influence of attached phase organic matter on the fate, transport and removal of carbon-based nanomaterials in porous media.
Escalating production and subsequent incorporation of engineered nanomaterials (ENMs) in consumer products increases the likelihood of release to the environment. Typically, hydrophobic particulate compounds released over time will accumulate in organic systems, including attached phase soil and sediment organic matter (AP-SOM). Especially in sediments, there is the potential for contaminants to persist for significant periods of time; therefore ENMs may impact environments long into the future. Although some effort has been devoted to investigate the behavior of ENMs in the environment, a very limited number of studies have focused on the interactions of AP-SOM and ENM. The goal of this proposal is to build systematic, mechanistic understanding of the interactions between ENM and AP-SOM and their influence on ENM transport. We focus on carbon-based ENMs by selecting multi-walled carbon nanotubes (MWCNT), fullerene (C60), and carbon nano-onions (CNOs) to represent cylindrical, spherical, and onion-shaped systems. Meanwhile, humic acid and kerogen are selected to represent soft/young and rigid/old AP-SOM. The central hypothesis is that the interactions between ENM aggregates and AP-SOM are affected by the fundamental nanostructure (e.g., different shapes) of ENMs and physicochemical characteristics (e.g., macromolecular rubbery/glassy states) of AP- SOM. An integrated experimental and modeling research framework is structured around four objectives: (1) Characterize SOM and ENMs to link physicochemical and macromolecular characteristics of AP-SOM and the fundamental nanostructure of ENM with their macroscopic interactions; (2) Quantify the interactions of nanomaterials and AP-SOM by conducting Quartz Crystal Microbalance (QCM) attachment/detachment experiments; (3) Quantify the influence of AP-SOM on the transport of nanomaterials in porous media by conducting column experiments; and (4) Develop and experimentally validate a mathematical model that is capable of simulating nanomaterial transport in porous media in the presence of AP-SOM. The proposed research can be transformative because it aims to link fundamental nanostructure and properties to the behaviors of ENM aggregate transport, with a particular focus on the presence of AP-SOM.
As the pace of research and production of nanomaterials continues to increase, comprehensive studies on the environmental impact of these materials are urgently needed. Understanding the fate and transport of nanomaterials in porous media will provide critical information on the influence of engineered nanomaterials on ecosystems and human health. The numerical simulator developed from this proposal can be used to predict the mobility distance of engineered nanomaterials under a range of environmental conditions, which can assist regulatory agencies in developing improved, risk-based guidelines that address these emerging contaminants. The advancement in our fundamental knowledge of nanoparticle retention in porous media can also be used to model the performance of filtration technologies for treatment of drinking water or wastewater containing nanoparticles. The project will initiate significant advancements in motivating undergraduates and graduates in the STEM areas by involving underrepresented groups in the project and transferring research results into the classroom. The fundamental knowledge, experimental techniques, and modeling tools produced from this work will be rapidly disseminated to the scientific community in the form of journal publications and presentations at regional, national, and international professional meetings.