title: Facet-Dependent Oxidative Goethite Growth As a Function of Aqueous Solution Conditions.
abstract: Nitroaromatic compounds are groundwater pollutants that can be degraded through reactions with Fe(II) adsorbed on iron oxide nanoparticles, although little is known about the evolving reactivity of the minerals with continuous pollutant exposure. In this work, Fe(II)/goethite reactivity toward 4-chloronitrobenzene (4-ClNB) as a function of pH, organic matter presence, and reactant concentrations was explored using sequential-spike batch reactors. Reaction rate constants were smaller with lower pH, introduction of organic matter, and diluted reactant concentrations as compared to a reference condition. Reaction rate constants did not change with the number of 4-ClNB spikes for all reaction conditions. Under all conditions, oxidative goethite growth was demonstrated through X-ray diffraction, magnetic characterization, and transmission electron microscopy. Nonparametric statistics were applied to compare histograms of lengths and widths of goethite nanoparticles as a function of varied solution conditions. The conditions that slowed the reaction also resulted in statistically shorter and wider particles than for the faster reactions. Additionally, added organic matter interfered with particle growth on the favorable {021} faces to a greater extent, with statistically reduced rate of growth on the tip facets and increased rate of growth on the side facets. These data demonstrate that oxidative growth of goethite in aqueous systems is dependent on major groundwater variables, such as pH and the presence of organic matter, which could lead to the evolving reactivity of goethite particles in natural environments.
authors.affiliation: Department of Chemistry, University of Minnesota , 207 Pleasant Street Southeast, Minneapolis, Minnesota 55455-0431, United States.
authors.forename: Jennifer H
authors.initials: JH
authors.lastname: Strehlau
authors.affiliation: Department of Psychology, University of Minnesota , 75 East River Road, Minneapolis, Minnesota 55455-0366, United States.
authors.forename: Melissa S
authors.initials: MS
authors.lastname: Stemig
authors.affiliation: Department of Chemistry, University of Minnesota , 207 Pleasant Street Southeast, Minneapolis, Minnesota 55455-0431, United States.
authors.forename: R Lee
authors.initials: RL
authors.lastname: Penn
authors.affiliation: Department of Civil, Environmental, and Geo-Engineering, University of Minnesota , 500 Pillsbury Drive Southeast, Minneapolis, Minnesota 55455-0116, United States.
authors.forename: William A
authors.initials: WA
authors.lastname: Arnold
mesh_terms: D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D058085:Iron Compounds / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry; D010084:Oxidation-Reduction; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D058085:Iron Compounds; D008903:Minerals; D014867:Water; D007501:Iron