Preparation and properties of core-shell TiO₂/SiO₂/CoFe₂O₄ and TiO₂/CoFe₂O₄ photocatalysts

Core-shell magnetic TiO₂ photocatalyst prepared by depositing an anatase layer onto magnetic materials has been found to be an effective way for recycling nano-TiO₂ particles from slurry systems. In the full paper, we present our experimental results on core-shell magnetic TiO₂/SiO₂/CoFe₂O₄ and TiO₂/ CoFe₂O₄ photocatalysts using spinel CoFe₂O₄ as core. In this abstract, we just add some pertinent remarks to listing the two topics of presentation. The first topic is: Experiments. In topic 1, we point out that TiO₂/SiO₂/CoFe₂O₄ and TiO₂/CoFe₂O₄ powders were prepared by reverse microemulsion system or wet chemical method and the activity of the as-prepared composites were tested through the degradation of TNT. The second topic is: Experimental results and their discussion. The four subtopics of topic 2 are: The effect of crystalline condition of CoFe₂O₄ nano-powders on the properties of TiO₂/CoFe₂O₄ composites (subtopic 2.1), the XRD (X-Ray Diffraction) analysis of TiO₂/SiO₂/CoFe₂O₄ (subtopic 2.2), TEM (Transmission Electron Microscopic) analysis (subtopic 2.3) and photocatalyst activity characterization (subtopic 2.4). In subtopic 2.1, we point out that impurities formed in TiO₂/CoFe₂O₄ composites produced by reverse microemulsion system are due to the direct deposition of TiO₂ onto amorphous CoFe₂O₄ core, and that impurities do not exist in composites obtained from wet chemical method. In subtopic 2.2, we point out that, with the introduction of SiO₂ middle layer, the diffraction pattern strength of CoFe₂O₄ is reduced while that of TiO₂ is enhanced. In subtopic 2.3, TEM pictures of four kinds of particles were given in Fig. 7 in the full paper. In subtopic 2.4, we point out that the activities of the four as-prepared composites rank in the following order: TiO₂/SiO₂/CoFe₂O₄ > TiO₂ > TiO₂/CoFe₂O₄ > SiO₂/CoFe₂O₄. In short, if non-crystalline CoFe₂O₄ is taken as core, impurities between core and shell form, and, with the introduction of SiO₂ middle layer, the catalytic activity of the magnetic core-shell photocatalyst improves.