PEI-modified chromium-based metal organic framework for Cr(VI) removal from aqueous solution

The chelating adsorbent PEI-MIL-101(Cr) was prepared by introducing polyethyleneimine (PEI) into the MIL-101(Cr) channel in this paper. X-ray diffractometer, Fourier transform infrared spectrometer and scanning electron microscope were applied to characterize the structure and morphology of MIL-101(Cr) and PEI-MIL-101(Cr). The adsorption properties and mechanism of the MIL-101(Cr) and PEI-MIL-101(Cr) to Cr(VI) were studied. The results showed that adsorption capacity of PEI-MIL-101(Cr) for Cr(VI) was obviously better than MIL-101(Cr). The adsorption isotherm of Cr(VI) onto MIL-101(Cr) and PEI-MIL-101(Cr) can be described by Langmuir model. The maximum adsorption amount for Cr(VI) onto MIL-101(Cr) and 30% PEI-MIL-101(Cr) was 61.99 and 40.34 mg/g. The adsorption kinetic data of the two adsorbents followed the pseudo second-order model. The negative values ΔH and ΔG illustrate that the process is spontaneous and exothermic. PEI-MIL-101(Cr) can be reused for four times.