title: Particle size and aggregation effects on magnetite reactivity toward carbon tetrachloride.
abstract: Nanoparticulate magnetite is found in many natural and engineered environments. This study characterized the reactivity of this material toward carbon tetrachloride (CCl4). Particle diameter plays an important role, with nominal (9 nm) magnetite suspensions exhibiting greater reactivity on both mass (k(m)) and surface area normalized (k(SA)) bases than (80 nm) magnetite suspensions. For the (9 nm) suspension, the aggregation state of the particles affects the measured km values. At 0.001 M ionic strength and pH 7, k(m) (=0.052-0.139 L g(-1) h(-1)) was as much as seven times larger than at 1 M (k(m) = 0.025-0.030 L g(-1) h(-1)). This decrease in reactivity with an increase in ionic strength is related to the measured diameter of the aggregates present in solution, thus implicating aggregate size as an important variable. This work is the first to indicate that both particle size and aggregation state must be considered when evaluating the reactivity of nanoparticle suspensions with groundwater contaminants.
authors.affiliation: The Charles E. Via Jr. Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24060, USA. pvikes@vt.edu
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Vikesland
authors.forename: April M
authors.initials: AM
authors.lastname: Heathcock
authors.forename: Robert L
authors.initials: RL
authors.lastname: Rebodos
authors.forename: K Erik
authors.initials: KE
authors.lastname: Makus
mesh_terms: D002251:Carbon Tetrachloride / Q000737:chemistry*; D052203:Ferrosoferric Oxide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009994:Osmolar Concentration; D010084:Oxidation-Reduction; D010316:Particle Size; D013696:Temperature