Aggregation of stabilized TiO2 nanoparticle suspensions in the presence of inorganic ions

The present study aims to evaluate the effect of inorganic ions on the aggregation kinetics of stabilized titanium dioxide (TiO2) nanoparticle (NP) suspension, an NP mode widely used in consumer goods and in aquatic environments. The point of zero charge of stabilized TiO2 NPs was approximately pH 6.5. The particle size of the stabilized TiO2 NP suspensions increased with the increase in salt concentrations. The additional salts caused the shift of zeta potentials of TiO2 suspensions to a lower value. The TiO2 NPs aggregated more obviously in the presence of anions than cations, and the effect of divalent anions was larger than that of monovalent anions. The critical coagulation concentration (CCC) values for commercial TiO2 NP suspensions with positive surfaces were estimated as 290 and 2.3 meq/L for Cl− and SO 42−, respectively. These CCC values of stabilized TiO2 NP suspensions are higher than those of TiO2 NP powders, indicating greater stability of the commercial stabilized TiO2 NP suspensions. The effects of commercial TiO2 NP suspensions still need to be explored and defined. Derjaguin–Landau–Verwey–Overbeek (DLVO) analysis can explain the aggregation behaviors of stabilized TiO2 NP suspensions. Such an understanding can facilitate the prediction of NP fate in the environment. Environ. Toxicol. Chem. 2012; 31: 1693–1698. © 2012 SETAC