Hexavalent chromium removal from water by ionic liquid modified metal-organic frameworks adsorbent

• Published in: Microporous and mesoporous materials 2017-05, Vol.243, p.47-55
• Main Authors: Nasrollahpour, A., Moradi, S.E.
• Format: Article
• Language: English
• Subjects: Chromate ion; Ionic liquid; Iron oxide nanoparticles; Langmuir isotherm; Metal-organic frameworks; Sorption
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/j.micromeso.2017.02.006

In this work, carbonized Ag core metal-organic frameworks (MOFs) shell was prapered and used for the removal of some PAHs. The structural order and textural properties of the metal-organic frameworks were studied by X-ray powder diffraction (XRD), thermogravimetric (TGA), BET surface area, and Fourier transform infrared spectroscopy (FTIR) analysis. Batch sorption experiments were conducted to study the effect of contact time, initial concentration and agitation speed for the removal of chromate ion from aqueous solution. The sorption was maximum for the initial pH of 2.0. The kinetic data were best fitted to the pseudo-second order model. The sorption of metal-organic frameworks to chromate ion fits to the Langmuir model with R2 of 0.9998, χ2 of 0.092 and qmax at 285.71 mg/g. Values of thermodynamic parameters viz. ΔG°, ΔH° and ΔS° were calculated and found to be −6.7 kJ/mol, 126.4 kJ/mol and 31.4 kJ/mol.K, respectively at 298 K. The values of ΔG° were found to be negative at all temperatures indicating the spontaneity of the removal process. A positive value of ΔH° further confirms the endothermic nature of removal process. The higher sorption capacity of ionic liquids loaded metal-organic frameworks for chromate ion is mainly due to the ionic liquid groups loaded on the surface of metal-organic frameworks which can react with Cr(VI) to form a complex deposited on the surface of metal-organic frameworks. [Display omitted] •Synthesis & characterization of Fe3O4 NPs, MIL-100(Fe & IL-MIL-100(Fe)).•Comparative studies on capability of these sorbents for chromate ion removal were done.•The kinetic, mechanistic, and thermodynamic studies on the sorption process were done.•Sorption kinetic of chromate ion by IL-MIL-100(Fe) follows pseudo second order.•The sorptions of chromate ion by IL-MIL-100(Fe) were spontaneous and endothermic.