title: The influence of ionic strength and organic compounds on nanoparticle TiO2 (n-TiO2) aggregation.
abstract: This study investigated the aggregation of n-TiO2 in the presence of humic acid (HA) and/or 17β-estradiol (E2) under high ionic strength conditions simulating levels detected in landfill leachate. Aggregation of n-TiO2 was strongly influenced by ionic strength as well as ionic valence in that divalent cations (Ca(2+)) were more effective than monovalent (Na(+)) at the surface modification. HA or E2 enhanced aggregation of n-TiO2 in 20 mM CaCl2, however little aggregation was observed in 100 mM NaCl. Similarly, we observed only the increased aggregation of n-TiO2 in the presence of HA/E2. These results showed the critical role of particles' surface charges on the aggregation behaviors of n-TiO2 that HA plays more significantly than E2. However, the slightly increased zeta potential and aggregation of n-TiO2 in the combination of HA and E2 at both 20 mM CaCl2 and 100 mM NaCl means that E2 has influenced on the surface modification of n-TiO2 by adsorption. Based on the aggregation of n-TiO2 under high ionic strength with HA and/or E2, we simulated the mobility of aggregated n-TiO2 in porous media. As a result, we observed that the mobility distance of aggregated n-TiO2 was dramatically influenced by the surface modification with both HA and/or E2 between particles and media. Furthermore, larger mobility distance was observed with larger aggregation of n-TiO2 particles that can be explained by clean bed filtration (CFT) theory.
authors.affiliation: Department of Civil Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, United States; Division of Water Environmental Engineering Research, National Institute of Environmental Research, Ministry of Environment, Incheon 22689, Republic of Korea. Electronic address: jwlee76@korea.kr.
authors.forename: Jaewoong
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Civil Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, United States.
authors.forename: Shannon L
authors.initials: SL
authors.lastname: Bartelt-Hunt
authors.affiliation: Department of Civil Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, United States.
authors.forename: Yusong
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Civil and Architectural Engineering, University of Wyoming, Laramie, WY 82071, United States.
authors.forename: Erica Jeanne
authors.initials: EJ
authors.lastname: Gilrein
mesh_terms: D000327:Adsorption; D002122:Calcium Chloride / Q000737:chemistry; D002413:Cations, Divalent; D004958:Estradiol / Q000737:chemistry*; D005374:Filtration; D006812:Humic Substances; D007700:Kinetics; D053758:Nanoparticles / Q000737:chemistry*; D009994:Osmolar Concentration; D016062:Porosity; D012965:Sodium Chloride / Q000737:chemistry; D014025:Titanium / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D002413:Cations, Divalent; D006812:Humic Substances; D014874:Water Pollutants, Chemical; C009495:titanium dioxide; D012965:Sodium Chloride; D004958:Estradiol; D014025:Titanium; D002122:Calcium Chloride
keywords: Aggregation; E2; HA; IS; Mobility; n-TiO(2)