Design and Application of Magnetic Photocatalysts for Water Treatment. The Effect of Particle Charge on Surface Functionality

摘要

Core-interlayer-shell Fe 3 O 4 /SiO 2 /TiO 2 , CoFe 2 O 4 /SiO 2 /TiO 2 and BaFe 12 O 19 /SiO 2 /TiO 2 magnetic photocatalysts were obtained. A water-in-oil microemulsion system with suitable surfactants was used for functionalization of the magnetic core with silica interlayer and TiO 2 -based photocatalyst. Uncoated and coated particles were characterized by electrophoretic measurements, X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), specific surface area (BET) measurements, diffuse reflectance spectroscopy (DRS) and vibrating sample magnetometer (VSM) analysis. The pH of the solution and corresponding zeta potential was found to be essential for appropriate formation of ferrite core/silica interlayer/TiO 2 shell nanocomposite, since the electrical charge controls interactions during functionalization of the magnetic core particles. Thus, the development of multilayer structure in the isoelectric point (IEP) region enhanced adhesion of ferrite, silica and titania particles. The obtained Fe 3 O 4 /SiO 2 /TiO 2 , CoFe 2 O 4 /SiO 2 /TiO 2 and BaFe 12 O 19 /SiO 2 /TiO 2 nanocomposites revealed superparamagnetic behavior. The decomposition rate of phenol and carbamazepine allowed to estimate their photocatalytic activity. Progress of photocatalytic mineralization of organic compounds was evaluated by total organic carbon (TOC) measurements. Photocatalytic activity measured in four subsequent cycles showed good reusability as no loss of efficiency of phenol degradation was observed.