Effect of dry grinding on the microstructure of palygorskite and adsorption efficiency for methylene blue

Palygorskite (PAL) was treated by a facile grinding technology. The effects of dry grinding treatment on the morphology, crystal structure, specific surface area, pore structure of PAL were explored by Fourier transform infrared (FTIR) spectra, field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) and UV/visible techniques. FESEM and XRD results showed that the dry grinding treatment could dissociate the crystal bundles of PAL, but the aspect ratio of rod-like crystals was decreased. As PAL with dry grinding treatment of 2 times, the great enhancement in specific surface area of 153 to 229 m2/g, micropore area of 28 to 103 m2/g, micropore volume of 0.012 to 0.047 cm3/g was observed. It was confirmed that the dry grinding treatment is favorable to generate mesopores and micropores, but almost has no influences on the total pore volume and external surface area. The adsorption efficiencies of grinded PAL for methylene blue (MB) were enhanced owing to the availability of more shielded adsorption sites and increasing specific surface area, micropore volume and mesopore volume.