Synthesis and characterization of radiation sensitive TiO2/monazite photocatalyst

A TiO2/monazite photocatalyst was prepared by embedding TiO2 nanoparticles into a monazite substrate surface. TiCl4 hydrolysis/citric acid chelating procedure under acidic conditions were used to synthesize the nanophase TiO2 particles. The anatase TiO2/monazite photocatalyst surface area, morphology, crystalline and elemental concentrations were characterized using Brunauer-Emmett-Teller (BET) method, scanning electron microscopy (SEM), X-ray diffraction (XRD), and inductively coupled plasma-atomic emission spectrometry (ICP-AES). Monazite contains a large amount of Ce-, La-, Nd- and Th-PO4 compounds; it has been known as a natural mineral material with minor radioactivity. TiO2-CeO2 composite is a kind of radiation sensitive photocatalyst in which the radiations of thorium nuclides give energy to trigger TiO2 and cerium ions which play an energy absorber with charge separator. The result showed that methylene blue and phenol were spontaneously photocatalytic decomposed by TiO2/monazite composite even in a dark environment. A synergistic effect was also examined with applied exterior UV or Co-60 irradiation. A hybrid mechanism is proposed; according by the radioluminescence (RL) from excited Ce ion by gamma-radiation soliciting CeO2/TiO2 heterojunction (HJ). This seems to be a possible mechanism to explain this self-activated photo-catalytic behavior.