不同结构偶氮染料在TiO_2纳米颗粒表面的吸附和光催化降解

Adsorption and Photocatalytic Degradation of Azo Dyes with Different Structures on the Surface of TiO_2 Nano-particles

为研究不同结构的水溶性偶氮染料在TiO2光催化剂表面的吸附和光催化降解行为,选择4种在印染工业中常用的水溶性偶氮染料:活性红MS、活性蓝B、酸性媒介黑PV和酸性橙156作为研究对象,分别考察在不同pH值和氯化钠存在条件下,TiO2光催化剂对它们的吸附行为和吸附模式,并通过数学模拟方法计算了其在TiO2光催化剂表面的吸附参数,还研究了它们在TiO2光催化剂表面的光催化降解反应.实验结果表明,4种水溶性偶氮染料在TiO2表面的吸附量随着pH值的升高逐渐降低,而且当pH值处于4～8之间时吸附量下降最为显著.在相同的吸附条件下,2种酸性染料在TiO2表面的吸附量高于2种活性染料,并且在氯化钠存在下它们的吸附量都得到不同程度的提高.水溶性偶氮染料的吸附过程符合Langmuir等温吸附模型,活性染料比酸性染料具有更高的吸附平衡常数和覆盖率.在TiO2对偶氮染料的光催化降解反应中,脱色率和反应速率常数随pH值的升高而降低,并且活性染料比酸性染料更易于发生光催化降解反应.

Four water-soluble azo dyes widely used for the dyeing and printing of fabrics including Reactive Red MS, Reactive Blue B, Mordant Black PV and Acid Orange 156 were selected to study the adsorption and photodegradation of water-soluble azo dyes with different structures on TiO2 particulate photocatalyst in water. And adsorption behavior and modes of these dyes on the surface of TiO2 particles were investigated under various pH levels and in the presence of sodium chloride, respectively. The adsorption parameters of the dyes were obtained using experimental data fitting method. In addition, these azo dyes were degraded photocatalytically in the presence of TiO2 photocatalyst under varied pH levels in water. The results indicated that high pH values caused low adsorption quantity of the dyes on TiO2 particles, and their adsorption decreased significantly with the pH range from 4 to 8. Moreover, the amounts of four dyes adsorbed on TiO2 particles were increased in the presence of sodium chloride, and those of the two acid dyes were much higher than the two reactive dyes in terms of the amounts adsorbed on TiO2 under the same conditions. In addition, the adsorption isotherms of four dyes were described well by Langmuir adsorption model, and the reactive dyes showed higher adsorption constants and coverage on the surface of TiO2 particles than the acid dyes. On the other hand, increasing pH values reduced the photocatalytic decoloration percentages and first order reaction rate constants, and the reactive dyes were decomposed more easily than the acid dyes under the same conditions.