Rio de Janeiro State University, Rio de Janeiro, Brazil.
Water Sci Technol. 2012;66(1):158-64. doi: 10.2166/wst.2012.154.
Reactive dyes are one of the major pollutants in textile wastewater and a concern because they are not easily degraded by conventional wastewater treatments. Heterogeneous photocatalysis has been considered an effective option for treating wastewater containing those dyes. This research work assesses the photocatalytic degradation of reactive dyes using UV irradiation and pure or impregnated ZnO. In addition to photocatalysis, separate photolysis and adsorption experiments were conducted but showed low efficiency. The dye degradation was monitored by UV-Vis spectroscopy and mineralization was determined by total organic carbon (TOC) analyses. Total color removal was achieved after 30 min of irradiation using pure ZnO. The Black 5 dye photocatalytic decolorization reaction followed first-order kinetics, while Yellow 145, Red 4 and Blue 21 dyes followed zero-order kinetics. TOC removals in the range of 70-80% were achieved after 240 min of individual photocatalytic treatment with ZnO. The performance of each photocatalyst was also compared when the four dyes were mixed together and the order of efficiency in the mineralization process was as follows: Fe/ZnO > ZnO > Co/ZnO. This result was explained by the crystal field theory.
活性染料是纺织废水中的主要污染物之一，也是人们关注的焦点，因为它们不容易被传统废水处理方法降解。多相光催化被认为是处理含有这些染料的废水的有效方法。本研究工作评估了使用 UV 照射和纯 ZnO 或浸渍 ZnO 对活性染料的光催化降解。除了光催化作用外，还进行了单独的光解和吸附实验，但效率较低。通过紫外-可见光谱监测染料降解，通过总有机碳 (TOC) 分析确定矿化程度。使用纯 ZnO 照射 30 分钟后，即可实现总色去除。黑 5 染料的光催化脱色反应遵循一级动力学，而黄 145、红 4 和蓝 21 染料遵循零级动力学。单独用 ZnO 进行光催化处理 240 分钟后，TOC 的去除率达到 70-80%。还比较了每种光催化剂在四种染料混合在一起时的性能，在矿化过程中的效率顺序如下：Fe/ZnO > ZnO > Co/ZnO。这一结果可以用晶体场理论来解释。
