Influences of environmental factors on aggregation of titanium dioxide nanoparticles
环境因素对纳米二氧化钛颗粒在水体中沉降性能的影响

The existing form of nano-TiO2, which determines its ecological risk, might be influenced by the ionic strength, pH, and dissolved organic matters (DOMs) of aqueous phase. This study focused on the stability of nano-TiO2 particles in aqueous solutions as a function of pH, ionic strength and DOMs. The results revealed that the aggregations of nano-TiO2 particles were related to pH and ionic strength of aqueous phase. The surface potential was higher as pH deviated from isoelectric points of nano-TiO2, resulting in less aggregated particles. As ionic strength of the solution increased, the particles would aggregate. DOMs could enhance the stability of nano-TiO2 particles in aqueous solutions, which might be related to the change of surface electric double layer and steric stabilization of nano-TiO2 particles. Fourier Transform Infrared Spectrum (FTIR) analysis of DOMs from different sources indicated that DOMs containing aromatic structures might pose higher influence on the stability of particles than those containing aliphatic hydrocarbon. The study suggested that nano-TiO2 particles may not be easily aggregate in natural water. Consequently, its ecological risk cannot be ignored.