Preparation Of TiO₂/SiO₂/Fe₃O₄ Magnetite Photocatalyst And Its Photocatalysis Of Bromamine Acid

TiO₂ photocatalyst, as a new functional material for environmental protection, was used in treating waste water widely. There were some disadvantages such as recycle difficulty for suspended TiO₂. In order to prolong the longevity of catalyst, we prepared magnetism composite particles, which can be recovered and reused.In this paper, nano-sized Fe₃O₄ particles were prepared by employing a coprecipitation method. By using the prepared Fe₃O₄ particles as nucleus, TiO₂/SiO₂/Fe₃O₄ composite particles were prepared by a sol-gel method with titanium n-butoxide (TBOT) and tetraethlorthosilicate (TEOS) as starting materials. The composite particles were characterized by using FTIR, AFM and XRD. The conditions of photocatalytic degradation such as pH, amounts of photocatalyst, initial concentration of bromamine acid, the addition of H2O₂, inorganic ion, etc, were studied in the decolorization of bromamine acid. Degradation kinetics and decoloration mechanisms of bromine acid were also studied. The results showed that SiO₂ and TiO₂ wraped on the suface of Fe₃O₄, and magnetic photocatalysts TiO₂/SiO₂/Fe₃O₄ had been prepared. When the solution pH was 4.0, the amount of TiO₂/SiO₂/Fe₃O₄ was 2.0g/L, the initial concentration was 30mg/L, the illumination time was 30min, the decolorization ratio and the remove rate of COD were 96.2% and 85.1%. After being used four times, the TiO₂/SiO₂/Fe₃O₄ had still a good photocatalytic activity and a high recycle efficiency. Supersonic was helpful for the photoactivity of the catalyst. There was an optimal quantity of the addition of hydrogen peroxide, Cu²⁺ and Fe³⁺. NO₃^- , Ca²⁺, Na+ had little effection photoactivity of the cataly. Mn²⁺, Cl—, HCO₃^- , SO₄^2-were found to restrain photoactivity of the cataly, but the action of SO₄^2- was not obvious.Within the initial concentration of 0-40mg/L, the photochemical decoloration reaction was expressed as first order kinetics, and the effect of initial concentration on the rate constant was: lnk1 = - 0.171l nC0- 2.360. The decoloration mechanism was that·OH and O₂^- which were produced in process of photocatalysis can change bromamine acid into small molecule products.