Adsorption mechanism of As(III) on polytetrafluoroethylene particles of different size. (November 2019)

• Record Type: Journal Article
• Authors: Dong, Youming; Gao, Minling; Song, Zhengguo; Qiu, Weiwen
• Is Part Of: Environmental pollution. Volume 254(2019)Part A
• Publication Date: 2019-11
• Subjects: Polytetrafluoroethylene -- Adsorption -- Hydrogen bond -- Exothermic process; 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.2019.07.118
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Microplastics exhibit active environmental behavior and unique surface characteristics, and act as carriers for the migration of trivalent arsenic (As(III)) in the environment. Herein, the mechanism by which polytetrafluoroethylene (PTFE) microplastic particles adsorb As(III) is systematically determined. The larger the size of PTFE particles, the smaller the specific surface area, the higher the point of zero charge (PZC), and the more unfavorable adsorption of As(III); the highest adsorption amount can reach 1.05 mg g −1 . The adsorption process can be divided into three stages by the intraparticle diffusion model: external mass transfer, intraparticle diffusion, and dynamic equilibrium, of which the external mass transfer stage is the adsorption rate-limiting stage. The Langmuir isotherm model better represented the equilibrium adsorption results. The adsorption of As(III) by PTFE was an exothermic process, and because the increase in temperature broke the hydrogen bond, the amount of adsorption was decreased, which was not conducive to spontaneous adsorption. In the pH range of 3–7, as the pH value increased, the amount of As(III) adsorbed by PTFE gradually decreased, which may be related to the change in PZC for PTFE and the protonation of As(III). The H on the surface hydroxyl group of the PTFE exhibited a very large positive potential (+82.37 kcal mol −1 ). Thus, it can attract the arsenic oxyanion, and As(III) was subsequently adsorbed on the surface of the PTFE through the hydrogen bond on the hydroxyl group. Electrostatic force and non-covalent interaction were the key mechanisms affecting the PTFE adsorption. Graphical abstract: Image 1 Highlights: Polytetrafluoroethylene (PTFE) microplastic particles have high adsorption capacity on As(III) (1.05 mg g −1 ). The adsorption of As(III) by PTFE is an exothermic process. The hydrogen atom in the surface hydroxyl group of the PTFE exhibited a very large positive electrostatic potential. Electrostatic force and non-covalent interaction are the key mechanisms affecting the As(III) adsorption by PTFE. Abstract : The key mechanisms of As(III) adsorption by PTFE is electrostatic force and non-covalent interaction.