Role of pH and ionic strength in the aggregation of TiO2 nanoparticles in the presence of extracellular polymeric substances from Bacillus subtilis

Environmental Pollution
Di LinPeng Cai

Abstract

Increased use of commercial titanium dioxide nanoparticles (TiO2 NPs) in consumer products most likely leads to their additional environmental release. Aggregation and disaggregation processes are expected to play an important role in the fate and transport of TiO2 NPs in natural aquatic ecosystems. Therefore, in this work, we have studied the colloidal stability of TiO2 NPs in the presence of extracellular polymeric substances (EPS) from Bacillus subtilis and the adsorption behavior of EPS on TiO2 NPs in aqueous solutions at different pH values and ionic strengths (IS). The adsorption and aggregation processes were found to depend on the solution chemistry. The mass fraction of EPS on TiO2 NPs decreased with increased pH and NaCl concentrations, which was verified by Fourier transform infrared spectroscopy. The presence of EPS can substantially influence the colloidal stability of TiO2 NPs. In deionized water, the aggregation of NPs was induced by the addition of EPS only when the pH was below the TiO2 NP point of zero charge (≈6). When the pH was equal to pHPZC, TiO2, the TiO2 NPs would rapidly form large aggregates, but the adsorption of EPS leads to partial fragmentation via electrostatic repulsion and steric hindrance. Whe...Continue Reading

Citations

Mar 17, 2021·Journal of Hazardous Materials·Yuling ChenChenxi Wu
Mar 18, 2020·Environmental Science & Technology·Shaohu OuyangXiangang Hu
Jan 8, 2019·Environmental Science & Technology·Ningyuan ZhuYonghong Wu
Jan 24, 2020·Ultrasonics Sonochemistry·Yihui WangXiaobing Wang

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