LINKING NANOGEOSCIENCE WITH WATER SUSTAINABILITY: A SURFACE CHEMISTRY APPROACH FOR UNDERSTANDING THE BEHAVIOR OF MINERAL NANOPARTICLES

Nanogeoscience is an emerging discipline where a growing number of earth scientists begin to measure, understand, and predict the change of earth material properties from the bulk to nanodomains, and to comprehend the significant ways that geologic processes are affected by these changes. Water sustainability can be better achieved by improving our knowledge on nanoparticle behaviors. With a typical concentration of 10 to 100 millions nanoparticles (NPs) per liter of natural water, nanoparticles are ubiquitous in the environment. Such natural NPs influence important geochemical processes such as soil genesis, biogeochemical cycling of elements, and contaminant transport/transformation.

Aggregation of NPs and their sorption on different environmental surfaces has important implication on their fate and transport in aquatic systems. Recent investigations point to the critical role of organics in altering the persistence and partitioning of NPs. Environmental organics exert influences on the binding of NPs by possessing different charges and hydrophobicity due to various exposed functional groups. This talk will highlight some of our recent and ongoing investigations on how properties of organics (from low to high complexity; i.e., from self-assembled monolayers to isolates of natural organic matter) interact with the surface characteristics of NPs and substrates to regulate NP adsorption dynamics. Case studies, including the insights gained from using iron oxide (hematite, α-Fe₂O₃) NPs and lead sulfide (galena, PbS) NPs as model NPs of metal oxides and metal sulfides, will be presented. With the use of surface-sensitive/nano-scale tools (e.g., quartz crystal microgravimetry), we revealed the critical role of surface modification in NP adsorption and the important of NP adsorption as a factor that control the transport of elements through the near-surface environment.