Adsorptive behaviors of methylimidazolium ionic liquids to a Y-type zeolite in water: Kinetics, isotherms, thermodynamics and interferences

- NaY is used to adsorb a methylimidazolium ionic liquid (BMIMCl) in water.
- Adsorption kinetics and isotherm of BMIMCl to NaY are measured and analyzed.
- Effects of temperature, pH and surfactants are investigated.
- Reusability of NaY is evaluated by solvent-washing and heat regenerations.
- Adsorption capacities of other methylimidazolium ILs to NaY are also measured.

We demonstrate the usage of industrially produced zeolites for adsorption of ionic liquids (ILs) in water using 1-butyl-3-methylimidazolium chloride (BMIMCl) as a representative IL and NaY as a typical Y-type zeolite. The adsorption behaviors of BMIMCl to NaY, are characterized by adsorption kinetics, isotherms, thermodynamics and interferences by other compounds. The pseudo 2nd order satisfactorily describes the adsorption kinetics, and thus the Langmuir isotherm is shown to be a suitable model for interpreting the isotherm data. The corresponding qmax of NaY for BMIMCl is 84 mg g− 1, higher than many reported carbonaceous and bio-derived adsorbents, and can be attributed to the electrostatic attraction between the negatively-charged NaY and cationic BMIM ions. The adsorption of BMIMCl to NaY is favorable and stable under neutral and alkaline conditions, whereas ions and ionic surfactants significantly interfere with adsorption. In addition, solvent-washing methods are less effective approaches to regeneration, whereas the used NaY can fully re-gain its adsorption capacity after heat treatment. The adsorption isotherms of other MIM-based ILs to NaY were also determined. We show that NaY, a readily available industrial material, is an effective adsorbent for BMIMCl. The behaviors revealed here can be valuable and critical for further investigating adsorptive removal of ILs from water and interaction of ILs to zeolites in water.

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