Synthesis And Photocatalytic Properties Of Aluminate Spinels

Photocatalyst of spinel structure has been attracted extensive attention because of its short band gap and high photocatalytic activity. The current work primarily investigates the preparation and photocatalytic properties of transition metal aluminate spinels.First, a series of transition metal aluminate spinel photocatalysts were synthesized by organic precursor method: CoAl₂O₄, NiAl₂O₄, CuAl₂O₄ and ZnAl₂O₄. These samples were characterized by TG-DTA, FTIR, XRD, TEM and UV-VIS DRS.The result suggested that CoAl₂O₄, NiAl₂O₄ and ZnAl₂O₄ transform into pure aluminate spinel phases except CuAl₂O₄. An intermediate CuO phase disappeared at 900℃in the calcination of CuAl₂O₄ precursor. It is found that CuAl₂O₄ which band gap is 1.92eV shows higher photocatalytic efficiency in the photocatalysis reaction which were evaluated by using methyl orange as degradation target.Optimum conditions in the preparation of CuAl₂O₄ were investigated. The CuAl₂O₄ photocatalysts were characterized by XRD and the activities were evaluated by using methyl orange as degradation target. The experimental results showed that temperature-gradient method (calcined at 600℃for 3 hours and then calcined at 800℃for 0.5 hour) can improve photocatalytic activity of CuAl₂O₄ effectively. The samples have been analyzed with FTIR spectroscopy and some discussions were made on the mechanism of organic precursor method.Finally, the effect of different light source, the initial concentration of methyl orange solution, the pH value of solution, the catalysts concentration, etc. on the photocatalytic efficiency have also been investigated. The results showed CuAl₂O₄ has high photocatalytic activity under visible light irradiation in the photodegradation of methyl orange, and its photocatalytic efficiency was in inverse proportion to initial concentration of methyl orange solution; neutral condition favored this reaction of the degradation of methyl orange by CuAl₂O₄; the best dosage of CuAl₂O₄ is 0.1g in the degradation of methyl orange(10 mg/L) which dosage is 0.5mg.