This study intended to characterize the fate of nano-TiO2 including powder (TiO2(P)) and suspension forms (TiO2(S)) in simulated drinking water treatments. Nano-TiO2 of 0.1 mg/L, 1.0 mg/L and 10 mg/L in deionized water and raw waters were prepared to assess the effects of water matrix on behaviors of nano-TiO2. After simulated treatments, the residual Ti concentrations ranged from 2.7% to 47.4% in different treatment units and the overall removal efficiencies were between 52.6% and 97.3%, except for the group of 0.1 mg/L nano-TiO2. The overall removal efficiencies for the group of 0.1 mg/L nano-TiO2 ranged between 9.3% and 53.5%, although no clear trend was observed. Sedimentation (after coagulation) and filtration were the most important processes to remove nano-TiO2 due to their agglomeration, which was confirmed by size distributions and zeta potential determination. The sizes of nano-TiO2 increased up to 4490.3 nm in the supernatants after sedimentation. Filtration further removed the agglomerates larger than 1 �m to have low Ti residual. Zeta potential analyses showed that anionic functional groups or negative charged natural organic matters were adsorbed onto the nano-TiO2 surfaces to decrease the zeta potentials. The surfactant additives in TiO2(S) increased the dispersion of nano-TiO2 and lead to lower removal rates. Furthermore, the nano-TiO2 particles were covered by viscous substances to form caramel-candy-like appearances in SEM images after chlorination or coagulation.

Characterization of titanium dioxide nanoparticles in simulated drinking water treatment processes

248th National Meeting (2014)

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