UV/H_2O_2降解水中磺胺嘧啶影响因素及机理

Influencing factors and mechanism of sulfadiazine degradation by UV/H_2O_2

利用UV/H_2O_2光氧化反应器降解水中的磺胺嘧啶,考察了H_2O_2投量、pH值、紫外功率等因素对去除效果的影响,同时对反应动力学及降解产物进行了分析。结果表明,在紫外辐照与H_2O_2氧化共同作用下,UV/H_2O_2降解水中磺胺嘧啶效果显著,去除率达90%以上,其降解过程符合一级反应动力学模型(R2=0.991 2)。H_2O_2投量与磺胺嘧啶降解速率常数具有良好的线性关系,H_2O_2投量由0.03增大至1.50 mmol·L-1,反应速率常数由0.048 2增大至0.359 9 min-1;同时,随着紫外灯功率由5增大至15 W,反应速率常数由0.066 2增大至0.163 1 min-1;随着初始磺胺嘧啶浓度由0.02增加至0.08 mmol·L-1,反应速率常数由0.251 7逐渐降低至0.046 8 min-1;pH由3.0升高至7.0,反应速率常数由0.070 2增大至0.102 3 min-1,当pH继续增大时,反应速率常数反而降低。根据液相色谱/质谱(LC/MS)对中间产物分析,UV/H_2O_2降解磺胺嘧啶生成质荷比(m/z)为173、186和200的对氨基苯磺酸等中间产物,推测S—N键和C—N键被打开,这些中间产物可进一步被降解,但TOC去除率仅为7%,表明磺胺嘧啶仅部分被矿化。UV/H_2O_2工艺处理磺胺嘧啶的电能效率(EEO)采用每一对数减少级电能输入进行评价,优化条件下电能效率为0.078 k Wh·m-3,可为实际工程应用提供参考。

The UV/H2O2 photo-oxidation reactor was applied to degrade sulfadiazine solution. The effect of n2O2 concentration, initial pH value, UV light power and sulfadiazine concentration on removal efficiency were investigated. The reaction kinetics and degradation products were also analyzed to full understand the degradation process. The results showed that the UV/H2O2 process was effective for the degradation of sulfadiazine with a removal efficiency above 90% , and the degradation process fitted well with the first-order kinetics model （R2 = 0. 991 2）. There had a satisfied linear relation between the degradation rate and H2O2 dosage. The degradation rate increased from 0. 048 2 to 0. 359 9 min -1 when the H2O2 dosage increased from 0.03 to 1.50 mmol · L-1The degradation rate also increased from 0. 066 2 to 0. 163 1 min-1 with an increase of UV light power from 5 to 15 W. In contrast, the degradation rate decreased from 0. 251 7 to 0. 046 8 min-1 with an increase of sulfadia- zine concentration from 0.02 to 0.08 mmol· L-1. The pH value also can affect the degradation rate, which in- creased from 0. 070 2 to 0. 102 3 rain-1 when pH value increased from 3.0 to 7.0. However, the degradation rate decreased to 0. 050 2 min-l when pH value increased to 11.0. The resuhs of liquid chromatography-mass spectrometry （LC/MS） suggested that three intermediate degradation-products were formed with a mass-to-charge ratio （m/z） of 173, 186 and 200, respectively. It was indicated that S--N bonds and N--N bonds were broken in the process, and the intermediate products can further degraded. However, the results showed that only 7% ofTOC was removed, indicating that only small part of sulfadiazine were mineralized. Finally, the electrical energy per order （EEO） was used to evaluate the cost of sulfadiazine degradation process in UV/H2O2 photo-oxidation reactor. The results showed that the EEO was only 0. 078 kWh· m-3 at the optimum conditions, which can pro- vide a reference for practical engineering application.