Adsorption of polyhydroxy fullerene on polyethylenimine-modified montmorillonite

The environmental behaviors and potential ecotoxicity of carbon nanomaterials, such as fullerene and its derivatives, are gaining ever-increasing concerns at present. This work attempts to develop an adsorbent for the effective removal of polyhydroxy fullerene (PHF) from aqueous solution, which was synthesized by modifying montmorillonite (Mt) with a branched polymer polyethylenimine (PEI). The adsorption results showed that the obtained adsorbent (i.e., PEI-Mt) could effectively remove PHF over a wide range of solution pH; both the electrostatic attraction and hydrogen-bond interaction between PHF and PEI-Mt contributed to the strong adsorption. Decreasing solution pH and rising PEI loading amount on Mt could both increase the adsorption amounts of PHF on PEI-Mt The adsorption isotherms could be well fitted with the Langmuir model, and the calculated maximum adsorption value of PHF on 10%PEI-Mt reached similar to 213 mg/g, much higher than that on the original Mt (similar to 16 mg/g). The adsorbents after PHF adsorption were further characterized using Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy. The results suggested that the adsorbed PHF primarily existed on the outer surfaces of PEI-Mt. This work showed that PEI-Mt can be a potentially efficient adsorbent for the removal of PHF from aqueous solution. (C) 2016 Elsevier B.V. All rights reserved