光降解柠檬酸酸洗废水的机理

Photo-degradation Mechanism of Citric Acid Pickling Wastewater

针对高浓度柠檬酸酸洗废水的光降解过程,以水杨酸为羟基自由基(·OH)捕获剂,通过紫外分光光度法检测产物2,3-二羟基苯甲酸在510 nm处的吸光度,以证实·OH的存在。以对苯二甲酸为·OH捕获剂,315 nm为激发波长,利用荧光分光光度法测定2-羟基对苯二甲酸在425 nm处的荧光强度,间接测定柠檬酸酸洗废水中·OH的浓度。检测结果表明:利用1stopt v1.5软件中的拟牛顿法和通用全局优化法对试验结果进行拟合,得出决定因数DC=0.993 2,说明水杨酸的光解过程较好地符合两步一级反应模型,证实光降解过程中有·OH产生。对苯二甲酸浓度为4×10^(-5)mol/L时,荧光强度与反应时间线性关系较好(R^2=0.999 8),即光照过程中·OH的浓度约为4×10^(-5)mol/L。

In order to study the photo-degradation process of high concentration citric acid pickling wastewater,the absorbancy of 2,3-dihydroxy-benzoic acid was measured by UV spectrophotometry at 510 nm with salicylic acid as capture agent to confirm the existence of hydroxyl free radicals( ·OH). Terephthalic acid was used as capture agent to measure the fluorescence intensity of 2-hydroxy terephthalicacid at 425 nm( excitation at 315nm) by fluoresence spectrophotometry,and to determine the concentration of · OH in citric acid pickling wastewater indirectly. The results show that determination coefficient( DC) is 0. 993 2 by the Quasi Newton method and global opitimization method of Istopt v1. 5 software,which suggests the photodissociation process of salicylic acid is fitted for two-step first order reaction model. The existence of ·OH in photolysis process is proved. The linear relationship between fluorescence intensity and reaction time is better( R2= 0. 999 8) when the concentration of terephthalicacid is 4 × 10- 5mol / L which suggest that the concentration of · OH is4 × 10- 5mol / L in photolysis process.