Preparation And Photocatalysis Of The Nano-TiO₂Mixed Crystals Suspension

Titanium dioxide is a very well-known and well-researched material due to thestability of its chemical structure, biocompatibility, physical, optical, and electricalproperties. Its photocatalytic properties have been utilized in various environmentalapplications to remove contaminants from both water and air. Titania-basedphotocatalytic systems are used for a variety of applications such as decomposition ofunwanted and toxic organic compounds, destruction of pollutants from contaminatedwater and air and killing of harmful bacteria and cancer cells. The unique feature of thephotocatalytic process is that it breaks down the pollutants and harmful organiccompounds into simple molecules such as carbon dioxide and water. In recent year,mixed crystals photocatalysts with rutile-anatase compositions have been reported toexhibit enhanced photoactivity relative to single-phase titania. The synthesis andapplication of nanometric mix-crystals of TiO₂have attracted much attention. Here, aseries nanometric mix-crystals of rutile and anatase TiO₂were prepared, andphotocatalysis properties are also investigated.The nanometric mixed crystals of rutile and anatase TiO₂were prepared byhomogeneous precipitation method using TiCl₄as titanium source. The effects of pHand reaction time on the ratio of nanometer TiO₂mix-crystals and photocatalysis werestudied. The prepared samples were also characterized by X-ray diffraction （XRD）,transmission electron microscopy （TEM） and laser diffraction particle size analyzer.The results show that nanometer TiO₂mix-crystal with good photocatalytic activity andstorage stability can be obtained under the reaction conditions: pH=0.5, normal pressure,95℃for5h. The prepared nanometer TiO₂mix-crystal consisting of anatase of72.7wt.%and rutile of27.3wt.%is oblong with an average size of15nm in length and5nm inwidth.The nanometric mixed crystals of rutile and anatase TiO₂also could be prepared byhomogeneous precipitation method using both TiCl₄and TiCl₃as titanium source. Theresults show that nanometer TiO₂mix-crystal with good photocatalytic activity andstorage stability can be obtained under the reaction conditions: The ratio of TiCl₄toTiCl₃is4to1, pH=0.5, normal pressure,95℃for6h. The prepared nanometer TiO₂mix-crystal consisting of anatase of63.9wt.%and rutile of36.1wt.%is circle with anaverage size of25nm. The photocatalysis activities of nano-TiO₂mixed crystals suspension werecharacterized by quantifying the degradation of Rhodamine B dye solution. The resultindicated that the product using TiCl₄as titanium source exhibited the bestphotocatalytic efficiency. The best photocatalytic efficiency can be obtained under thereaction condition: pH=5, Solids content of suspension is0.1wt.%. In the reaction,replace Rhodamine B with Methyl orange or Methylene blue, the product also exhibitedgood photocatalytic activity.In summary, the preparation of nano-TiO₂mixed crystals suspension byhomogeneous precipitation method was simple and had low cost, high maneuverability.The nano-TiO₂mixed crystals suspension prepared with good photocatalytic activityand storage stability. Therefore, this work provides an ideal way to prepare nano-TiO₂mixed crystals suspension.