title: Effect of UV irradiation on the aggregation of TiO2 in an aquatic environment: Influence of humic acid and pH.
abstract: The behavior of photoactive TiO2 nanoparticles in an aquatic environment under UV irradiation was investigated. When there was no UV light irradiation, the attachment of humic acid (HA) onto the TiO2 nanoparticles improved their stability due to an increase in the electrostatic and steric repulsions between the particles. However, our study demonstrated that UV light clearly influenced the aggregation of TiO2 nanoparticles. Half an hour of UV irradiation caused the particles to aggregate from 331.0 nm to 1505.0 nm at a pH of 3.0. Similarly, the particles aggregated from 533.2 nm to 1037.0 nm at a pH of 6.5 and from 319.0 nm to 930.0 nm at a pH of 9.0. The aggregation continued with increased irradiation time, except for the condition at pH 3.0, which demonstrated disaggregation. Furthermore, we determined that the photocatalytic degradation of the HA dominated the behavior of TiO2 in our study. From the results of HA removal and 3DEEM fluorescence spectra data for the solution, a change in the HA was in accordance with the size change of the TiO2. The results illustrated that the UV irradiation affected the behavior of light-active nanomaterial (such as TiO2) in an aquatic system, thus influencing their bioavailability and reactivity.
authors: Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, China.
authors: Peifang
authors: P
authors: Wang
authors: Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, China.
authors: Ning
authors: N
authors: Qi
authors: Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, China. Electronic address: andyao@hhu.edu.cn.
authors: Yanhui
authors: Y
authors: Ao
authors: Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, China.
authors: Jun
authors: J
authors: Hou
authors: Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, China.
authors: Chao
authors: C
authors: Wang
authors: Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, China.
authors: Jin
authors: J
authors: Qian
mesh_terms: D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D053768:Metal Nanoparticles / Q000737:chemistry*; D055672:Static Electricity; D014025:Titanium / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D006812:Humic Substances; C009495:titanium dioxide; D014025:Titanium
keywords: Aggregation; Aquatic environment; Humic acid; Titanium dioxide; UV irradiation