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Enhanced Transport of TiO2-Reduced Graphene Oxide Nanocomposites in Saturated Porous Media: the Impact of Loaded TiO2 Shape and Solution Conditions

Authors
  • Cao, Jiajing1
  • Bai, Xue1, 1
  • Ye, Zhengfang2
  • Chen, Wei1
  • Ge, Haoyu1
  • Ding, Yuanyuan1
  • Hua, Zulin1
  • 1 Hohai University, Nanjing, 210098, People’s Republic of China , Nanjing (China)
  • 2 Department of Environmental Engineering, Peking University, The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing, 100871, People’s Republic of China , Beijing (China)
Type
Published Article
Journal
Water Air & Soil Pollution
Publisher
Springer-Verlag
Publication Date
Mar 10, 2020
Volume
231
Issue
3
Identifiers
DOI: 10.1007/s11270-020-04492-3
Source
Springer Nature
Keywords
License
Yellow

Abstract

Laboratory sand column experiments were conducted to model the transport behavior of TiO2 nanoparticle-reduced graphene oxide nanocomposite (TiO2 NP/rGO) and TiO2 nanowire-reduced graphene oxide nanocomposite (TiO2 NW/rGO) using different electrolyte solutions and pH values. The breakthrough curve of TiO2/rGO nanocomposite shows that the mobility is highly sensitive to ionic strength and pH. Experimental results found that the zeta potential of TiO2 NW/rGO is more negative due to more hydroxide ions in solution from the TiO2 NWs. The mobility of TiO2 NW/rGO is slightly greater than that of TiO2 NP/rGO at lower ionic strength (1–50 mM NaCl and 1–5 mM CaCl2), whereas at 10 mM CaCl2, TiO2 NW/rGO had weak transport because of physical straining. The ratio of the hydrodynamic diameter (4214 nm) to sand diameter was as high as 0.83. Mobility increased for both TiO2 NP/rGO and TiO2 NW/rGO with respect to ionic strength because of electrostatic repulsions. When the pH was 9 with a 10 mM NaCl background solution, the stronger energy barrier between the nanocomposite and sand contributed to the enhanced transport behavior. However, with a solution at pH 3–6, the ripening effect controlled the transport of TiO2 NW/rGO. The normalized concentrations rapidly climbed to a maximum (0.05 and 0.14) and then decreased gradually after 2 pore volumes. In general, these behaviors may well predict the fate of carbon-based nanoparticles with tailwater or wastewater flowing into soil environments. Graphical Abstract

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