title: Transport of stabilized iron nanoparticles in porous media: Effects of surface and solution chemistry and role of adsorption.
abstract: Carboxymethyl cellulose (CMC) stabilized zero-valent iron (ZVI) (CMC-ZVI) nanoparticles have been extensively tested for remediation of soil and groundwater. This study investigated effects of iron oxide and aluminum oxide on retention and transport of CMC-ZVI nanoparticles, which have a mean hydrodynamic diameter of 155nm. Column breakthrough experiments showed that the metal oxides coatings on quartz sand greatly enhanced particle retention. A mechanistically sounder transport model was proposed by incorporating a Langmuir-type adsorption rate law into the classic convection-dispersion equation with the adsorption parameters derived from independent experiments. The model allows for a quantitative evaluation of the role of adsorption. While filtration is the primary mechanism for particle retention at lower pore velocities, adsorption becomes more significant at elevated velocities. The presence of 40-80mg-CL-1of natural organic matter and high ionic strength (up to 200mM CaCl2) had negligible effect on the breakthrough profiles of the nanoparticles. Starch, a neutral polysugar stabilizer, was also tested as a stabilizer. Starch-stabilized ZVI nanoparticles, with a mean hydrodynamic diameter of 303nm, displayed a higher particle retention than CMC-ZVI. The information and modeling approach can facilitate our understanding of fate and transport of stabilized ZVI nanoparticles under various geochemical conditions.
authors.affiliation: Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849, USA; Geosyntec Consultants, Inc., Minneapolis, MN, USA.
authors.forename: Man
authors.initials: M
authors.lastname: Zhang
authors.affiliation: College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou, China. Electronic address: fenghe@zjut.edu.cn.
authors.forename: Feng
authors.initials: F
authors.lastname: He
authors.affiliation: Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849, USA. Electronic address: zhaodon@auburn.edu.
authors.forename: Dongye
authors.initials: D
authors.lastname: Zhao
authors.affiliation: The R & D Center for Sustainable Environmental Biotechnology, Beijing University of Civil Engineering and Architecture, Beijing, China.
authors.forename: Xiaodi
authors.initials: X
authors.lastname: Hao
keywords: Aluminum oxide coated sand; Iron oxide coated sand; Stabilized nanoparticles; Transport modeling; Zero-valent iron