磷钨酸光催化脱色直接橙S溶液的实验研究

Photocatalytic Decolorization of Direct Orange S Solution by Phospho-tungstic Acid

染料废水排放前必须加以控制,杂多酸光催化可以有效地降解颜料废水,但对其动力学和光催化机理尚需进一步研究.以磷钨酸为光催化剂,在紫外灯照射下,对模拟染料废水直接橙S溶液进行光催化脱色反应.研究了磷钨酸质量浓度、pH值、直接橙S溶液初始质量浓度和羟基自由基捕获剂对直接橙S溶液脱色反应的影响.结果表明:对20 mg/L的直接橙S溶液,磷钨酸最佳加入质量浓度为0.4 g/L;pH值最佳值为2.0;当直接橙S溶液低于35 mg/L,直接橙S溶液的光催化脱色反应符合Langmuir-Hinshelwood(L-H)动力学方程;随着光照时间的延长直接橙S溶液能被有效矿化;羟基自由基捕获剂能抑制光催化脱色反应.研究结果对理解杂多酸光催化过程提供了有益的参考.

It is crucial to control and treat the effluents of dyes before being released into the aquatic environment.The dyes can be degraded effectively by polyoxometalate photocatalysis,but the kinetics and photocatalytic mechanism have been seldom concerned.Photocatalytic decolorization of direct orange S（DOS） solution was studied by utilizing phospho-tungstic acid as photocatalyst under ultraviolet irradiation.The effect of catalyst concentration,pH value,the initial concentration of direct orange S solution and hydroxyl radicals scavengers added on decoloration reaction of direct orange S solution were investigated.The experimental results show that the optimal concentration of photocatalyst is 0.4 g / L and the optimal pH value is 2.0.The kinetic results show that the decolorization process is a pseudo first order reaction and Langmuir-Hinshelwood model can well describe this process when concentration of DOS is below 35 mg / L.Furthermore,the addition of NaBr,Na2SO4,methanol,ethanol and tertbutyl alcohol can inhibit the decolorization reaction greatly,which indicates that the hydroxyl radicals exist in the reaction system.DOS can be degraded effectively with phosphotungstic acid under ultraviolet irradiation.The results of this study are beneficial to understand polyoxometalate photocatalysis process.