环境因素对纳米二氧化钛颗粒在水体中沉降性能的影响

纳米二氧化钛进入水体环境后,其存在形态可能受离子强度、pH和溶解性有机质的影响,进而影响其生态风险.因此,本文考察了纳米二氧化钛颗粒在不同环境条件下的沉降性能.结果显示,纳米二氧化钛在水体中聚集程度与体系的pH值有关,pH值偏离颗粒的等电点时,颗粒的表面电位越高,越不容易聚集;水体离子强度的增加可促进纳米颗粒聚集,而水体中广泛存在的溶解性有机质可使纳米二氧化钛颗粒在水中的稳定性增强,这与颗粒表面的扩散双电层和空间位阻的变化有关.通过对不同来源溶解性有机质的结构进行分析发现,溶解性有机质中所含的芳香性结构对颗粒稳定性的影响大于脂肪烃结构.纳米二氧化钛颗粒可在自然水体中迁移,不易沉降,因此,其对水生生态系统的影响不容忽视.

Influences of environmental factors on aggregation of titanium dioxide nanoparticles

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.