Studies On The Preparation, Characterization Of Magnetic Photocatalytic Compound And Photoreduction To Cr(VI)

Photocatalytic technology has special advantages in the treatment of wastewater with heavy metal ions, especially, the treatment of wastewater which has complicated compositions and low concentration, so this technology has a promising prospect.At present, the research about TiO₂ form has two tendencies: one is TiO₂ powder, another is TiO₂ membrane. Compared with TiO₂ membrane, TiO₂ powder has the larger surface; therefore, its photocatalytic activity is higher. But TiO₂ powder is difficult to be separated from reactants for its small particle diameter. Especially in the system of industrial wastewater, TiO₂ powder has big lost rate when to be separated. In order to solve the problem of TiO₂ powder's separation and reuse, we prepared magnetic photocatalyst.Our methods are as follows: by using micron-sized Fe₃O₄ as support, prepare TiO₂ and SiO₂ coatings on the surface of Fe₃O₄ to get TiO₂/Fe₃O₄ and TiO₂/SiO₂/Fe₃O₄ by sol-gel method. The results indicated that using HCOOH as catalyst to prepare SiO₂ coating had a better effect by sol-gel process; TiO₂/SiO₂/Fe₃O₄ has better magnetic performances and photocatalytic activity than that of TiO₂/Fe₃O₄. Then we deposited noble-metal Ag and Pt on the surface of TiO₂/SiO₂/Fe₃O₄ by the photodeposition method. The results indicated that the deposition of noble metal had effects to the magnetic performances of photocatalyst TiO₂/SiO₂/Fe₃O₄; compared with TiO₂/SiO₂/Fe₃O₄, the photocataltic activity of Ag/TiO₂/SiO₂/Fe₃O₄ could increase with a suitable Ag loading, but the photocataltic activity of Pt/TiO₂/SiO₂/Fe₃O₄ was all reduced with varying Pt loadings.Finally, using Cr(â…¥) aqueous solution as object to evaluate the photocatalytic activity of samples, and we also investigated the effect of the concentration of Cr(â…¥) aqueous solution, the amount of catalyst, pH values and reuse times on the photocatalytic efficiency.