Nanomaterials released into the environment could cause a threat to our ecosystem and human health. Titanium dioxide, TiO2, and zinc oxide, ZnO, are two widely used nanoparticles (NPs) found in a large number of consumer products. This study aims to evaluate the mobility of two commercial stabilized NPs in aquatic environment. The properties of two NPs were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and dynamic light scattering (DLS). From FTIR spectrum, organic capping agents on commercial NPs could contribute its stability. The point of zero charges (PZC) of these two commercial TiO2 and ZnO NPs we used were about pH 6.5 and 10.3, respectively. The stability of commercial NP is independent on its concentration. NP trended to settle down when the aqueous pH near its pHpzc, and remained stable when the solution pH away from its pHpzc. In stable suspensions, TiO2 NPs settled down obviously at NaCl concentrations higher than 100 meq/L and 10 meq/L for ZnO. It was attributed to the surface charge of NPs neutralized by electrolytes. In the presence of low concentrations of Suwannee river humic acid (SRHA), TiO2 NPs did not settle down until SRHA concentration increased to 20 mg/L, which were stabilized again in the presence of SRHA of 50 mg/L. ZnO NPs did not settle down until SRHA concentration increased to 1 mg/L, which were stabilized again in the presence of SRHA of 10 mg/L. These better understandings can facilitate the prediction of NP removal and fate in the aquatic environment.

Effect of water chemistry on the sedimentation of two commercial nanoparticles in water

248th National Meeting (2014)

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