The interaction of nanoparticle titanium dioxide (n-TiO 2) with organic wastewater contaminants (OWCs): Mechanisms, stability, and transport

Abstract

Wastewater treatment plants (WWPTs) play an important role in the environmental release of wastewater contaminants via physical and biological processes. However, the vast majority of WWTPs can not completely eliminate organic or inorganic contaminants. Newly emerging contaminants such as steroid hormones, pharmaceuticals, and nanoparticles (NPs) (i.g. TiO₂) are released from WWTP effluent into receiving waters.

In this study, we investigate the interaction between trace organic wastewater contaminants and nanoparticles after release from WWTPs in the aquatic environment. First, we investigated the stability of n-TiO ₂ as a function of 17β-estradiol (E2) concentrations under various ionic strength conditions at fixed pH 7, which showed the effect of E2 on the stability and mobility of n-TiO₂. Second, we evaluated the stability of n-TiO₂ in the presence of humic acid (HA) and E2 concentration under high ionic strength conditions to simulate a landfill leachate. Third, quantitative structure-activity relationship (QSAR) models for prediction of n-TiO₂ aggregation by organic compound molecular descriptors were investigated using multiple linear regression (MLR) method. Finally, we evaluated the deposition of n-TiO₂ under different surface roughness using a new technique, quartz crystal microbalance with dissipation (QCM-D). We observed that surface roughness resulted in higher deposition of n-TiO ₂ under favorable condition compared to flat surfaces according to DLVO theory. These results represent the first effort to show the effects of surface roughness on the deposition of n-TiO₂.