Ionic liquids filled hybrid capsules by harnessing interfacial imine chemistry of Janus nanosheets stabilized pickering emulsion for removal of chlorophenols

Abstract

Ionic liquids filled hybrid capsules (C-IL) hold promise as extraction medium to remove phenolic endocrine disruptors (PEDs), which are priority pollutants because of their high persistence and toxicity. Nonetheless, preparation of uniformly sized C-IL has stand out as the major drawback for their use on adsorption applications. In this work, Janus graphene oxide (J-GO) nanosheets stabilized Pickering emulsion incorporated with interfacial imine chemistry were used for synthesis of polymer shell encapsulated 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6), and then as-prepared hybrid capsules (C-IL/W) were considered as a novel material for 3,4,5-trichlorophenol (3,4,5-TCP) capture. Uniformly sized C-IL/W (180 μm in diameter) had high IL content of 90 wt%, and its shell thickness from quick interfacial imine chemistry in situ is about 2.0 to 2.5 μm. Benefiting from the strong hydrogen bonding and π-π conjugation of the two aromatic rings with loaded [BMIM]PF6, the maximum adsorption capacity calculated from Langmuir model was 6775 mg g−1 at 25 °C for 3,4,5-TCP. Through the principal component analysis (PCA), the facts that chlorine substituent such as its number and location posed a significant influence on the PEDs extraction efficiency were confirmed, which followed the order: 2-chlorophenol (2-CP) < 2,6-dichlorophenol (2,6-DCP) < 2,4-dichlorophenol (2,4-DCP) < 3,4,5-TCP. The hydrophobicity and steric hindrance upon [BMIM]PF6 were the main factors affecting the extraction performance. After three regeneration cycles, the adsorption capacity of capsules towards 3,4,5-TCP was 79% of the first cycle, and the desorption efficiency was still above 90%. The results not only demonstrated an important method to design C-IL for PEDs removal, but also suggested the possible mechanism for chlorophenols extraction.