An integrated approach using ozone nanobubble and cyclodextrin inclusion complexation to enhance the removal of micropollutants. (15th May 2021)

• Record Type: Journal Article
• Authors: Fan, Wei; An, Wengang; Huo, Mingxin; Xiao, Dan; Lyu, Tao; Cui, Jingyu
• Is Part Of: Water research. Volume 196(2021)
• Publication Date: 2021-05-15
• Subjects: Advanced oxidation -- Chlorophenol -- Emerging organic contaminants -- Hpβcd -- Inclusion complex; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2021.117039
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: An integrated approach of nanobubbles and HP β CD was developed to enhance ozonation. The mass transfer coefficient of O3 was 4.7 times higher than conventional approach. Small amount of HP β CD addition prolonged 18 times longer lifespan of dissolved O3 . Mechanisms of inclusion were studied by direct detection and molecular simulation. This innovative method led to 7 times higher removal of the model micropollutant. Abstract: Ozone (O3 ) has been widely used for the elimination of recalcitrant micropollutants in aqueous environments, due to its strong oxidation ability. However, the utilization efficiency of O3 is constrained by its low solubility and short half-life during the treatment process. Herein, an integrated approach, using nanobubble technology and micro-environmental chemistry within cyclodextrin inclusion cavities, was studied in order to enhance the reactivity of ozonisation. Compared with traditional macrobubble aeration with O3 in water, nanobubble aeration achieved 1.7 times higher solubility of O3, and increased the mass transfer coefficient 4.7 times. Moreover, the addition of hydroxypropyl- β -cyclodextrin (HP β CD) further increased the stability of O3 through formation of an inclusion complex in its molecule-specific cavity. At a HPβCD:O3 molar ratio of 10:1, the lifespan of O3 reached 18 times longer than in a HP β CD-free O3 solution. Such approach accelerated the removal efficiency of the model micropollutant, 4-chlorophenol by 6.9 times, compared with conventional macrobubble ozonation. Examination of the HP β CD inclusion complex by UV–visible spectroscopy and Nuclear Magnetic Resonance analyses revealed that both O3 and 4-chlorophenol entered the HP β CD cavity, and Benesi-Hildebrand plots indicated a 1:1 stoichiometry of the host and guest compounds. Additionally, molecular docking simulations were conducted in order to confirm the formation of a ternary complex of HP β CD:4-chlorophenol:O3 and to determine the optimal inclusion mode. With these results, our study highlights the viability of the proposed integrated approach to enhance the ozonation of organic micropollutants. Graphic abstract: Image, graphical abstract