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Surface Changes and Impurity Release Kinetics of Titanium Dioxide Nanoparticles in Aqueous Environment
Citation:
Liu, X., G. Chen, J. Erwin, AND C. Su. Surface Changes and Impurity Release Kinetics of Titanium Dioxide Nanoparticles in Aqueous Environment. Presented at 243rd American Chemical Society (ACS) Spring 2012 National Meeting and Exposition.
Impact/Purpose:
Poster for the 243rd American Chemical Society National Meeting and Exposition, San Diego, CA, March 25-29, 2012
Description:
Previous studies have found the significant role of impurities (i.e., silicon, phosphorus) in the aggregation and sedimentation of TiO2 nanoparticles in water environment. However, it is not understood whether dissolution of the impurities potentially impacts the environment or the stability and fate of TiO2 NPs are affected during the dissolution process. In this study, we investigated the impurity dissolution kinetics and surface transformation of 5 types of TiO2 nanoparticles (i.e., 5, 10, and 50 nm anatase and 10 × 40, 30 × 40 nm rutile) at various pH and ionic strength. Both acidic and basic conditions accelerated the release of Si, while the basic conditions enhanced the P release greatly. The quantity of dissolved Si increased with increasing reaction time from 2 hr to 19 d in a power mode, while P released to the aqueous solution quickly within the first 2 hr. P dissolved from the 50 nm anatase reached 5000 to 7100 mg/Kg at neutral to alkaline pH, which indicated a potential pollutant source. The variation in impurity dissolution is consistent with the chemical composition of pristine TiO2, i.e., the most leachable quantity of Si for the 10 × 40 nm rutile and P for the 50 nm anatase, which was verified by Fourier transform infrared spectroscopy. The impurity dissolution did not change greatly within ionic strength of 20 – 50 mM at pH 8.4. Dynamic light scattering revealed relatively stable surface potential and particle size of the NPs during impurity release process.