Events & Media

The Bren School of Environmental Science & Management
at the University of California, Santa Barbara

Presents

A PhD DEFENSE

"Impact of solution constituents, natural stimuli, and material properties on
nanoparticle agglomeration in aqueous environments"

Dongxu Zhou
Bren School of Environmental Science & Management

Friday, June 22
9 a.m.
Bren Hall 1520 (Oak Room)

Arturo Keller, faculty advisor
Patricia Holden and Ram Seshadri, committee members

Abstract
Nanostructured materials are being integrated in a wide range of consumer and industrial products in the pursuit of outstanding electronic, photonic, thermal, or mechanical properties. As the nanomaterial production rises, there is a growing concern about the environmental risks of this emerging technology. Understanding the fate and transport of nanomaterials is the crucial first step toward a full assessment of such risks. Among the several key transport processes, agglomeration of nanoparticles controls their size and compactness and, thus, their deposition and transport in the water column. 

This doctoral research investigated the key factors that impact the process of nanoparticle agglomeration. Specifically, the factors studied include: (1) solution-chemistry parameters (such as pH, ionic strength, organic matter, and nanoparticle concentration); (2) the presence of clay particles; (3) material properties (particle size, morphology, and crystal structure); (4) sintered agglomerate structure.

The key findings are: (1) solution-chemistry parameters alter nanoparticle agglomeration by manipulating the inter-particle electrostatic repulsion; (2) heteroagglomeration between clay minerals and nanoparticles dramatically decreases nanoparticle mobility and therefore reduces their long-distance migration; (3) nanoparticles having the same chemical composition but varying material properties exhibit different colloidal stability; (4) both sunlight and temperature fluctuation can disagglomerate the metal-oxide nanoparticle clusters and thus enhance their mobility.