Hierarchical porous polymeric ionic liquids with excellent adsorption performance for phenolic compounds

In this work, polymeric ionic liquids (PILs) based on imidazolium ionic liquid monomer, which possessed hierarchical porous structure and rich Lewis basic sites, could effectively adsorb both large-sized and small molecular phenolic compounds from aqueous solution. The maximum adsorption capacities of the as-synthesized PILs for tannic add (TA), 4-nitrophenol (4-NP) and 4-chlorophenol (4-CP) reached as high as 911 mg/g, 460 mg/g and 433 mg/g, respectively. The capadty for TA was the highest among the existing adsorbents. The abundant Lewis basic sites (N-atom and Cl-) provided by imidazolium ionic liquids and the special hierarchical porous structure of PILs were responsible for its excellent phenolic adsorption performance. The adsorption equilibrium data of 4-NP and 4-CP fitted well with the Freundlich model while those of TA complied better with the Langmuir model. The mechanism analysis indicated that the adsorption for 4-NP and 4-CP was mainly due to pi-pi interactions, and that for TA was dominated by H-bonding and electrostatic interaction. The PILs could be easily regenerated. This study provided a novel material for the treatment of phenolic wastewater. (C) 2020 Elsevier B.V. All rights reserved.