Adsorption of caprolactam from aqueous solution by novel polysulfone microcapsules containing [Bmim][PF6]

• Ionic liquid [BMIM][PF6] has been encapsulated in polysulfone.
• The microcapsules containing ionic liquid have been used for the first time to extract caprolactam from water.
• The adsorption kinetics and sorption isotherm have also been discussed.

Polysulfone (PSF) microcapsules containing ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]) as extractant have been successfully prepared using solvent evaporation method and used in removing caprolactam from water. The results showed that ionic liquid [Bmim][PF6] was successfully encapsulated by PSF and the encapsulation capacity of 32.44% was achieved. Systematic studies on the effect of concentration of ammonium sulfate solution, caprolactam adsorption equilibrium, kinetic and isotherm by PSF@[Bmim][PF6] capsules were carried out. The results showed that increasing the concentration of ammonium sulfate solution, initial concentration of the caprolactam and the adsorption time were good for adsorption. The adsorption kinetics of caprolactam followed pseudo-second-order model and the Freundlich equation described the adsorption process better than the Langmuir equation. These PSF@[Bmim][PF6] capsules showed potential ability in the treatment of wastewater.

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