Environmentally relevant impacts of nano-TiO2 on abiotic degradation of bisphenol A under sunlight irradiation. (September 2016)

• Record Type: Journal Article
• Authors: Wu, Wei; Shan, Guoqiang; Wang, Shanfeng; Zhu, Lingyan; Yue, Longfei; Xiang, Qian; Zhang, Yinqing; Li, Zhuo
• Is Part Of: Environmental pollution. Volume 216(2016)
• Page Start: 166
• Page End: 172
• Publication Date: 2016-09
• Subjects: Nano-TiO2 -- Bisphenol A -- Degradation -- pH -- Humic acid; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2016.05.079
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Understanding the effects of nano-TiO2 particles on the environmental behaviors of organic pollutants in natural aquatic environments is of paramount importance considering that large amount of nano-TiO2 is being released in the environment. In this study, the effect of nano-TiO2 on the degradation of bisphenol A (BPA) in water was investigated under simulated solar light irradiation. The results indicated that nano-TiO2 at environmentally relevant concentration (1 mg/L) could significantly facilitate the abiotic degradation of BPA (also at low concentration) under mild solar light irradiation, with the pseudo first-order rate constant ( k obs ) for BPA degradation raised by 1–2 orders of magnitude. As reflected by the inhibition experiments, hydroxyl radicals (OHs) and superoxide radical species were the predominant active species responsible for BPA degradation. The reaction was affected by water pH, and the degradation rate was higher at acidic or alkaline conditions than that at neutral condition. Humic acid (HA) also affected the reaction rate, depending on its concentration. At lower concentration (the mass ratio of HA/nano-TiO2 was 0.1:1), HA improved the dispersion and stability of nano-TiO2 in aquatic environment. As a result, the yield of OHs by nano-TiO2 under sunlight irradiation increased and BPA degradation was facilitated. When the HA concentration increased, a coating of HA formed on the surface of nano-TiO2 . Although nano-TiO2 became more stable, the light absorption by nano-TiO2 was significantly reduced due to the strong light absorption of the HA coated on the surface. As a consequence, the yield of OH decreased and BPA degradation was depressed. The results imply that nano-TiO2 at low concentration may distinctly mediate BPA degradation, and can contribute to the natural attenuation of some organic pollutants in aquatic environment with low level of HA. However, this process would be significantly reduced in the presence of high level of HA. Graphical abstract: Highlights: Nano-TiO2 at environmentally relevant level facilitated BPA photo-degradation. BPA degradation was distinctly affected by water chemistry. More active species were generated in acidic or alkaline than neutral conditions. Low level of humic acid facilitated BPA degradation by promoting TiO2 dispersion. High level of humic acid depressed BPA degradation by forming a coat on TiO2 surface. Abstract : Nano-TiO2 at environmentally relevant level could facilitate BPA photo-degradation, which was distinctly affected by water chemistry, such as pH and humic acid.