可见光下TiO2还原Cr(Ⅵ)光催化反应研究

Photocatalytic Reduction of Cr(Ⅵ)by TiO2 under Visible Light

Cr(Ⅵ)是一种对生态环境和人类健康有极大危害的重金属离子,为研究可见光下TiO2还原Cr(Ⅵ)的光催化反应,首先使用溶胶-凝胶法制备TiO2光催化剂,并对其结构进行表征;然后在可见光下研究其还原Cr(Ⅵ)光催化反应;最后分析光催化反应机理及反应动力学。结果表明,制备的TiO2为锐钛矿,直径约为400~500 nm,禁带宽度为3.2 eV;在最佳条件(Cr(Ⅵ)初始浓度为1.00 mg/L,TiO2投加量为2.00 g/L,pH为4.00,甲醇浓度为0.10 mol/L)下反应150 min,TiO2还原Cr(Ⅵ)可见光催化效率可高达100%;可见光下TiO2催化反应机理为:HCrO4^-吸附在TiO2表面,形成一种具有可见光响应的HCrO4^-/TiO2复合催化剂;TiO2还原Cr(Ⅵ)光催化反应符合假一级反应动力学,反应速率常数为0.0058 min^-1。

Cr(Ⅵ)is a kind of heavy metal ion which is very harmful to ecological environment and human health.To study the photocatalytic reaction of TiO2 reduction Cr(Ⅵ)under visible light,TiO2 photocatalyst was prepared by sol-gel method firstly and its structure was characterized,then photocatalytic reduction for Cr(Ⅵ)with TiO2 was investigated,and lastly mechanism and kinetics were analyzed,respectively.Results displayed that the diameter of as-prepared TiO2 was about 400~500 nm and bandgap of it was 3.2 eV.TiO2 photocatalytic reduction efficiency was 100%when initial concentration of Cr(Ⅵ)was 1.00 mg/L,the dosage of TiO2 was 2.00 g/L and pH 4.00 in the presence of 0.10 mol/L methanol within 150 min.A novel complex photocatalyst HCrO4-/TiO2 is formed between TiO2 and HCrO4-which is the dominant existing form of Cr(Ⅵ),and photoinduced electrons are the reactant for Cr(VI)reduction.TiO2 photocatalytic reduction for Cr(Ⅵ)conforms to first-order kinetics and rate constant is 0.0058 min^-1.