TiO_2悬浆体系光催化降解酸性红B动力学分析

Kinetic analysis of photocatalytic degrada- tion of dye red B in aqueous suspension of TiO_2 powder

采用 Ti O2 悬浆体系 ,以高硼紫外灯为光源 ,考察了酸性红B光催化降解中溶液初始质量浓度、催化剂投加量、无机盐、空气通入量、p H值对光催化降解速率影响。用 Langmuir-hinshelwood方程描述酸性红 B光催化动力学行为。结果表明 :初始质量浓度增加 ,反应由一级向零级过渡 ;催化剂投加量在 0 .5～ 2 .5 g/ L时 ,3 0 mg/ L酸性红 B一级反应速率常数与投加量成线性关系 ;5种溶解性无机盐对光催化降解酸性红 B存在抑制作用 ,阴离子影响大于阳离子 ;通入空气影响动力学行为 ,改变反应级数。本实验在 p H值为 3时光催化降解效果最佳 ,且酸性条件下比碱性下条件效果更好 ;Ti O2 表面吸附能力随 p H值增大而减弱 。

The present paper aims at investigating the kinetics of degradation in aqueous Suspension of TiO_2 Powder. To this end, we have observed the phenomenon of photocatalytic degradation of dye red B in the powder at a distance of 10cm. from the lamp to the surface of the solution, in which the TiO_2 catalyst is prepared and used for the degradation by taking Ti(OC_4H_9)_4 as its raw material. The author has also done a detailed study of the effect of dye red B initial concentration on the photocatalytic degradation when added some catalyst, inorganic salts, aeration as well as pH value. The degradation mechanism has also been described by means of Langmuir-Hinshelwood (L-H) equation. Compared with the degradation at different conditions with UV-VIS scans, our experimental results indicate that UV light and catalyst are the necessary properties to determine the role of photocatalytic oxidation. With the increase of the initial concentration of dye red B, changes of the apparent rate constants can be found from the first-order reaction model to the zero one, which linearly follows the increase of the TiO_2 amount in the range of 2.5(g/L). Both anions (Cl^-, SO^(2-)_4) and cations (Na^+, K^+, Ca^(2+), Mg^(2+)) are likely to retard the rate with the former being the major factor. Here, it is the constant change that influences the aeration quantity that affects the kinetic behavior. When the decolorization in acid is done more efficiently, in alkali, the reaction would be going on with optimum pH value (pH=3). While pH keeps increasing, the absorption of dye red B would be reduced. Thus, the results prove that the kinetics of photocatalytic degradation of dye red B in Aqueous Suspension of TiO_2 powder can be explained by Langmuir-Hinshelwood (L-H) model, with the absorption existing in the degradation process.