title: Covalent triazine-based framework: A promising adsorbent for removal of perfluoroalkyl acids from aqueous solution.
abstract: Perfluoroalkyl acids (PFAAs) are highly stable, persistent, and ubiquitous in the environment with significant concerns growing with regards to both human and ecosystem health. Due to the high stability to both biological and chemical attack, the only currently feasible approach for their removal from water is adsorbent technology. The main objective of this study was to assess a covalent triazine-based framework (CTF) adsorbent for removal from aqueous solutions of perfluoro C4, C6, and C8 carboxylates and sulfonates including the two C8s most commonly monitored, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Adsorption affinity and capacity were quantified and compared to three commonly used sorbents: pulverized microporous activated carbon, single-walled carbon nanotubes, and Amberlite IRA-400 anion-exchange resin. CTF adsorbent exhibited pronouncedly higher adsorption affinity and capacity of PFAAs than other test sorbents. The remarkably strong adsorption to CTF can be attributed to the favored electrostatic interaction between the protonated triazine groups on the inner wall of the hydrophobic CTF pore and the negatively charged head groups of the PFAAs intercalated between the CTF layers. The homogeneous, nanosized pores (1.2 nm) of CTF hindered adsorption of a large-sized dissolved humic acid, thus minimizing the suppression of PFAA adsorption. Additionally, regeneration of CTF was easily accomplished by simply raising pH > 11, which inhibited the electrostatic adsorptive interaction of PFAAs.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse/School of the Environment, Nanjing University, Jiangsu, 210046, China.
authors.forename: Bingyu
authors.initials: B
authors.lastname: Wang
authors.affiliation: Department of Agronomy, Purdue University, West Lafayette, IN, 47907, USA.
authors.forename: Linda S
authors.initials: LS
authors.lastname: Lee
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse/School of the Environment, Nanjing University, Jiangsu, 210046, China.
authors.forename: Chenhui
authors.initials: C
authors.lastname: Wei
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse/School of the Environment, Nanjing University, Jiangsu, 210046, China.
authors.forename: Heyun
authors.initials: H
authors.lastname: Fu
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse/School of the Environment, Nanjing University, Jiangsu, 210046, China.
authors.forename: Shourong
authors.initials: S
authors.lastname: Zheng
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse/School of the Environment, Nanjing University, Jiangsu, 210046, China.
authors.forename: Zhaoyi
authors.initials: Z
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse/School of the Environment, Nanjing University, Jiangsu, 210046, China; School of Urban and Environmental Sciences, Peking University, Beijing, 100871, China. Electronic address: zhud@pku.edu.cn.
authors.forename: Dongqiang
authors.initials: D
authors.lastname: Zhu
mesh_terms: D000327:Adsorption; D017738:Alkanesulfonic Acids / Q000032:analysis*; D002210:Caprylates / Q000032:analysis*; D002606:Charcoal / Q000737:chemistry*; D005466:Fluorocarbons / Q000032:analysis*; D006801:Humans; D006812:Humic Substances / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D046529:Microscopy, Electron, Transmission; D008962:Models, Theoretical; D037742:Nanotubes, Carbon / Q000737:chemistry*; D013499:Surface Properties; D014227:Triazines / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D017738:Alkanesulfonic Acids; D002210:Caprylates; D005466:Fluorocarbons; D006812:Humic Substances; D037742:Nanotubes, Carbon; D014227:Triazines; D014874:Water Pollutants, Chemical; D002606:Charcoal; C023036:perfluorooctanoic acid; C076994:perfluorooctane sulfonic acid
keywords: Adsorption; Covalent triazine-based framework (CTF); Electrostatic interaction; Nanosized pore; Perfluoroalkyl acids (PFAAs)