Nishio Junpei, Tokumura Masahiro, Znad Hussein T, Kawase Yoshinori
Research Center for Biochemical and Environmental Engineering, Department of Applied Chemistry, Toyo University, Kawagoe, Saitama 350-8585, Japan.
J Hazard Mater. 2006 Nov 2;138(1):106-15. doi: 10.1016/j.jhazmat.2006.05.039. Epub 2006 May 20.
Photocatalytic decolorization of azo-dye Orange II in water has been examined in an external UV light irradiation slurry photoreactor using zinc oxide (ZnO) as a semiconductor photocatalyst. The effects of process parameters such as light intensity, initial dye concentration, photocatalyst loading and initial solution pH on the decolorization rate of Orange II have been systematically investigated. A two-stage photocatalytic decolorization of Orange II, the first stage of fast decolorization rate and the subsequent second stage of rather slow decolorization rate, was found. The efficiency of decolorization of Orange II increased as initial Orange II concentration decreased and UV light intensity increased. There was the optimal ZnO concentration being around 1000 mg L(-1). The optimal pH was around 7.7, which was at the natural pH of the dye solution. The effect of aeration rate on the decolorization of Orange II has been also investigated and the enhancement of decolorization of Orange II with increasing aeration rate was found. By using a model for the light intensity profile in the external UV light irradiation slurry photoreactor, the simulation model for the decolorization of Orange II with ZnO photocatalyst has been developed. The proposed model in which the slow decolorization in the second stage as well as the initial fast decolorization is also taken into account could simulate the experimental results for UV light irradiation satisfactorily. The proposed simulation model in which the change of light intensity with time due to the decolorization of Orange II and the light scatter due to solid photocatalysts are considered will be very useful for practical engineering design of the slurry photoreactor of wastewater including textile dyes.
在外部紫外光照射的悬浮液光反应器中，以氧化锌（ZnO）作为半导体光催化剂，对水中偶氮染料橙黄II的光催化脱色进行了研究。系统研究了光强、初始染料浓度、光催化剂负载量和初始溶液pH值等工艺参数对橙黄II脱色率的影响。发现橙黄II的光催化脱色分为两个阶段，第一阶段脱色速率快，随后第二阶段脱色速率相当慢。橙黄II的脱色效率随着初始橙黄II浓度的降低和紫外光强度的增加而提高。存在一个最佳的ZnO浓度，约为1000 mg L⁻¹。最佳pH值约为7.7，这是染料溶液的自然pH值。还研究了曝气速率对橙黄II脱色的影响，发现随着曝气速率的增加，橙黄II的脱色增强。通过使用外部紫外光照射悬浮液光反应器中光强分布的模型，建立了用ZnO光催化剂对橙黄II脱色的模拟模型。所提出的模型考虑了第二阶段的缓慢脱色以及初始的快速脱色，能够令人满意地模拟紫外光照射的实验结果。所提出的模拟模型考虑了由于橙黄II脱色导致的光强随时间的变化以及固体光催化剂引起的光散射，对于包括纺织染料在内的废水悬浮液光反应器的实际工程设计将非常有用。
