title: Functionalized magnetic mesoporous silica nanoparticles for U removal from low and high pH groundwater.
abstract: U(VI) species display limited adsorption onto sediment minerals and synthetic sorbents in pH <4 or pH >8 groundwater. In this work, magnetic mesoporous silica nanoparticles (MMSNs) with magnetite nanoparticle cores were functionalized with various organic molecules using post-synthetic methods. The functionalized MMSNs were characterized using N2 adsorption-desorption isotherms, thermogravimetric analysis (TGA), transmission electron microscopy (TEM), (13)C cross polarization and magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectroscopy, and powder X-ray diffraction (XRD), which indicated that mesoporous silica (MCM-41) particles of 100-200nm formed around a core of magnetic iron oxide, and the functional groups were primarily grafted into the mesopores of ∼3.0nm in size. The functionalized MMSNs were effective for U removal from pH 3.5 and 9.6 artificial groundwater (AGW). Functionalized MMSNs removed U from the pH 3.5 AGW by as much as 6 orders of magnitude more than unfunctionalized nanoparticles or silica and had adsorption capacities as high as 38mg/g. They removed U from the pH 9.6 AGW as much as 4 orders of magnitude greater than silica and 2 orders of magnitude greater than the unfunctionalized nanoparticles with adsorption capacities as high as 133mg/g. These results provide an applied solution for treating U contamination that occurs at extreme pH environments and a scientific foundation for solving critical industrial issues related to environmental stewardship and nuclear power production.
authors.affiliation: Savannah River National Laboratory, Aiken, SC 29808, USA. Electronic address: dien.li@srs.gov.
authors.forename: Dien
authors.initials: D
authors.lastname: Li
authors.affiliation: Department of Chemistry, University of Iowa, Iowa City, IA 52242, USA.
authors.forename: Shani
authors.initials: S
authors.lastname: Egodawatte
authors.affiliation: Savannah River National Laboratory, Aiken, SC 29808, USA.
authors.forename: Daniel I
authors.initials: DI
authors.lastname: Kaplan
authors.affiliation: Department of Chemistry, University of Iowa, Iowa City, IA 52242, USA.
authors.forename: Sarah C
authors.initials: SC
authors.lastname: Larsen
authors.affiliation: Savannah River National Laboratory, Aiken, SC 29808, USA; Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, USA.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Serkiz
authors.affiliation: Savannah River Ecology Laboratory, University of Georgia, Aiken, SC 29802, USA.
authors.forename: John C
authors.initials: JC
authors.lastname: Seaman
keywords: Acidic and alkaline groundwater; Magnetic mesoporous silica nanoparticles; Surface functionalization with organic molecules; Uranium removal