Effect of grinding time on fabricating a stable methylene blue/palygorskite hybrid nanocomposite

The nanoscale dispersion of the crystal bundles or aggregates of natural palygorskite (PAL) is the key factor to prepare a stable PAL-based hybrid nanocomposite. The appropriate grinding process can effectively disaggregate the crystal bundles of PAL as dispersed nanorods and promote its interaction with organic molecules. In this study, a series of methylene blue/palygorskite (MB/PAL) hybrid nanocomposites were prepared by a facile mortar grinding process, and the effects of grinding time on their structure and stability were intensively investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FIR) spectra, Brunauer-Emmett-Teller (BET), thermal gravimetric analysis (TGA) and UV-vis techniques, as well as the resistance tests to acid, heat and UV-light. It was found that the control of grinding time is the key point affected the stability of hybrid structure, because it greatly influenced the removal of the water molecules, the change of d-spacing of (110) crystal plane and the organic/inorganic interaction between MB molecules and PAL. The aggregates of PAL crystals were highly dispersed as individual nanorods after being ground for 30 min, and the MB molecules are more easily to be adsorbed on the nanorods of PAL or be encapsulated in their channels, so the thermal stability, acid and UV-light resistance of the nanocomposites were evidently enhanced. (C) 2015 Elsevier B.V. All rights reserved.