The influence of ionic strength and organic compounds on nanoparticle TiO2 (n-TiO2) aggregation

• Published in: Chemosphere (Oxford) Vol. 154; pp. 187 - 193
• Main Authors: Lee, Jaewoong, Bartelt-Hunt, Shannon L., Li, Yusong, Gilrein, Erica Jeanne
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.07.2016
• Subjects: Adsorption; Aggregation; Calcium Chloride - chemistry; Cations, Divalent; Estradiol - chemistry; Filtration; Humic Substances; Kinetics; Mobility; n-TiO2; Nanoparticles - chemistry; Osmolar Concentration; Porosity; Sodium Chloride - chemistry; Titanium - chemistry; Water Pollutants, Chemical - chemistry; Aggregation; Mobility; n-TiO2; HA; IS; E2; n-TiO
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2016.03.059

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 (Ca2+) 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. •The significant aggregation of n-TiO2 in the presence of HA and/or E2 is ionic valence dependent.•HA has a major influence on the aggregation and zeta potential values of n-TiO2.•Larger aggregation of n-TiO2 in the coexistence of HA and E2 led to a larger mobility distance in porous media under favorable condition.