title: Dynamic and thermodynamic mechanisms of TFA adsorption by particulate matter.
abstract: Trifluoroacetic acid (TFA) in the atmosphere is produced by degradation of hydrochlorofluorocarbons and hydrofluorocarbons. In recent years, TFA has attracted global attention because of increased environmental concentrations, biological toxicity and accumulation in aqueous environments. This study focused on the mechanisms underlying the adsorption of TFA by particulate matter to identify the appropriate descriptive model for this process and thus improve estimation of TFA adsorption in future environmental monitoring. Onsite gas and particle phase sampling in Beijing, China, and subsequent measurement of TFA concentrations indicated that the TFA concentration in the gas phase (1396 ± 225 pg m-3) was much higher than that in the particle phase (62 ± 8 pg m-3) and that monthly concentrations varied seasonally with temperature. Based on the field results and analysis, an adsorption experiment of TFA on soot was then conducted at three different temperatures (293, 303, and 313 K) to provide parameters for kinetic and thermodynamic modelling. The proportion of atmospheric TFA concentration in the gas phase increased with temperature, indicating that temperature affected the phase distribution of TFA. The subsequent kinetic and thermodynamic modelling showed that the adsorption of TFA by soot could be described well by the Bangham kinetic model. The adsorption was controlled by diffusion, and the key mechanism was physical adsorption. The adsorption behavior can be well described by the Langmuir isotherm model. The calculated thermodynamic parameters ΔG° (-2.34, -1.25, and -0.15 kJ mol-1at 293, 303, and 313 K, respectively), ΔH° (-34.34 kJ mol-1), and ΔS° (-109.22 J mol-1K-1) for TFA adsorption by soot were negative, indicating that adsorption was a spontaneous, exothermic process.
authors.affiliation: State Key Joint Laboratory for Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China.
authors.forename: Junyu
authors.initials: J
authors.lastname: Guo
authors.affiliation: State Key Joint Laboratory for Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China.
authors.forename: Zihan
authors.initials: Z
authors.lastname: Zhai
authors.affiliation: State Key Joint Laboratory for Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.affiliation: State Key Joint Laboratory for Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China.
authors.forename: Ziyuan
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Safety and Environmental Protection Research Center of China, Waterborne Transport Research Institute, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wu
authors.affiliation: State Key Joint Laboratory for Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China.
authors.forename: Boya
authors.initials: B
authors.lastname: Zhang
authors.affiliation: State Key Joint Laboratory for Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China. Electronic address: jbzhang@pku.edu.cn.
authors.forename: Jianbo
authors.initials: J
authors.lastname: Zhang
mesh_terms: D000327:Adsorption; D000068476:Beijing; D002681:China; D004784:Environmental Monitoring; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D052638:Particulate Matter; D053260:Soot; D013696:Temperature; D013816:Thermodynamics; D014269:Trifluoroacetic Acid / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D006812:Humic Substances; D052638:Particulate Matter; D053260:Soot; D014874:Water Pollutants, Chemical; D014269:Trifluoroacetic Acid
keywords: Adsorption; Kinetic model; Langmuir isotherm model; Particulate matter; Trifluoroacetic acid