Adsorption of perfluoroalkyl acids on granular activated carbon supported chitosan: Role of nanobubbles. (December 2022)

• Record Type: Journal Article
• Authors: Liu, Wei; Lin, Tao; Zhang, Xue; Jiang, Fuchun; Yan, Xiaoshu; Chen, Han
• Is Part Of: Chemosphere. Volume 309:Part 1(2022)
• Publication Date: 2022-12
• Subjects: PFAAs -- Nanobubbles -- Chitosan -- Granular activated carbon -- Adsorption mechanism; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2022.136733
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: The safety threat posed by Perfluoroalkyl acids (PFAAs) in drinking water is a growing concern. In this study, we loaded chitosan (CS) on granular activated carbon (GAC) to adsorb PFAAs, and we explored the role of nanobubbles in the adsorption process through experiments and density functional theory (DFT) calculations. Compared with GAC, we found that the use of the composite adsorbent (CS/GAC) enhanced the removal rate of perfluorooctanoic acid by 136% with the assistance of nanobubbles. PFAAs with different chain lengths have different adsorption mechanisms owing to surface activity differences. PFAAs with longer C–F chains can be directly enriched with amino groups on the CS or air–water interface on composite adsorbents. Additionally, PFAAs can be enriched with nanobubbles in solution to form nanobubble–PFAA colloids, which are adsorbed by protonated amino groups on CS through electrostatic interactions. We found that PFAAs with shorter C–F chains are less affected by nanobubbles, and DFT calculations indicated that the adsorption of short-chain PFAAs is mainly affected by electrostatic interactions. We also proved that the electrostatic interactions between CS and PFAAs are mainly derived from the abundant protonated amino groups. Graphical abstract: Image 1 Highlights: The contribution of nanobubbles in CS/GAC adsorption of PFAAs was investigated. PFAAs adsorption is facilitated through the air-water interface and electrostatic interactions. The improvement in removal rate depends on the length of the perfluoroalkyl linkages. Protonated amino groups provide a positive potential for the adsorption of PFAAs. The adsorption mechanism of PFAAs with different chain lengths is proposed.