Synthesis, adsorption and photocatalytic property of halloysite-TiO2-Fe3O4 composites

摘要

Halloysite-TiO2-Fe3O4 composites were prepared by sequentially depositing anatase TiO2 and magnetic Fe3O4 particles on the halloysite nanotube (HNT) surfaces. HNT-TiO2 and HNT-TiO2-Fe3O4 composites were characterized by transmission electron microscopy, energy dispersive X-ray spectroscopy, specific surface analyzer, and X-ray diffraction. The surfaces of HNTs were attached with the aggregates of TiO2 and Fe3O4 nanoparticles, the contents of which were calculated to be about 15.2 and 1.5 wt% in HNT-TiO2-Fe3O4. The adsorption and photodegradation of methylene blue (MB) by HNT-TiO2 and HNT-TiO2-Fe3O4 were studied. HNT-TiO2-Fe3O4 exhibited the faster adsorption process than HNT-TiO2. The kinetic adsorption followed the pseudo-second-order model and the isotherm data fitted the Langmuir model well. The maximum adsorption capacities of MB were 28.07 and 27.27mg/g for HNT-TiO2 and HNT-TiO2-Fe3O4, respectively. HNT-TiO2-Fe3O4 possessed the better removal capability of MB from the aqueous solution than HNT-TiO2. About 100% MB was removed for HNT-TiO2-Fe3O4 under UV light irradiation for 12h, in contrast with about 80% MB removal for HNT-TiO2. HNT-TiO2-Fe3O4 exhibited higher photocatalytic activity for the persistent organic pollutant 4-nitrophenol than HNT-TiO2. HNT-TiO2-Fe3O4 and can be easily separated from the aqueous solution with the magnetic rather than the filtration or centrifugation.