Real-time monitoring of nanoscale TiO2 concentration by spectrophotometry: Implications of agglomeration due to natural organic matter and multivalent ions.

The study of the environmental fate of nanoscale TiO2 (n-TiO2) is a major recent research focus which requires a rapid and accurate on-site concentration determination method. Inductively coupled plasma mass spectroscopy (ICP-MS) has been the most widely used method for determining the concentration of n-TiO2 in environmental samples; however, poses many challenges, such as hazardous hydrofluoric acid pre-treatment and clear limitations in mobile on-site measurement and monitoring. This study demonstrates that industrial wastewater containing natural organic matter (NOM) can present a major challenge to the analysis of n-TiO2 by ICP-MS, and introduces a spectrophotometry technique that can be used as an alternative. The results suggest that spectrophotometry methods can be more accurate than slurry nebulization ICP-MS for measuring the concentrations of n-TiO2 in wastewater containing NOM under low salt conditions. Furthermore, this study demonstrates the use of a portable flow-through spectrophotometer for use in applications of wastewater treatment and environmental monitoring with real-time feedback of n-TiO2 concentrations. The ability to detect and monitor n-TiO2 will greatly assist in improving the understanding of hazards and risks that emerging nanomaterials pose to the environment and the public health.