US/O3降解对硝基苯酚的影响因素及机理

研究了US（超声波）/O₃（臭氧）体系中气速、温度、pH值、对硝基苯酚初始质量浓度以及超声声强对对硝基苯酚降解速率的影响.研究结果表明：对硝基苯酚降解速率随着气速、超声声强及pH值（pH≤6时）的提高而提高，随着对硝基苯酚初始质量浓度的提高而下降，而反应温度及在pH>6时影响不明显.对硝基苯酚在US/O₃、US及O₃体系中的降解均遵循拟一级反应动力学规律，其反应速率常数分别为1.50×10^-3 s^-1、3.27×10^-5 s^-1和6.63×10^-4 s^-1，增强因子为216％，具有明显的协同效应，其协同效应主要是由臭氧在空化泡内热解产生•OH引起的.采用液相色谱（HPLC）、离子色谱(IC)、GC-MS等方法测定出对硝基苯酚降解的主要中间产物有邻苯二酚、邻苯醌、对苯二酚、对苯醌、苯酚、反丁烯二酸、顺丁烯二酸、草酸和甲酸等，并依此推导出对硝基苯酚的降解机理.

Influencing factors and mechanism of decomposition of 4-nitrophenol by US/O3

The effects of gas flow rate, temperature, pH value, initial mass concentration of 4-nitrophenol solution, and ultrasonic intensity on the decomposition efficiency of 4-nitrophenol by ultrasonic irradiation and ozone were studied. The results showed that the decomposition efficiency of 4-nitrophenol increased with the increase of gas flow rate, ultrasonic intensity and pH values (pH≤6), and decreased with the increase of initial mass concentration of 4-nitrophenol solution, while both temperature and pH value (pH>6) were relatively not effective. The decomposition reactions of 4-nitrophenol by US/O₃, US and O₃ separately follow pseudo-first-order kinetics with rate constants 1.50×10^-3 s^-1，3.27×10^-5 s^-1 and 6.63×10^-4 s^-1 respectively, and the enhancement factor of 4-nitrophenol decomposition was around 216%. Ultrasound decomposed ozone,providing •OH augmentation,which was the main cause of synergetic effect. The main intermediates during the decomposition included catechol, o-benzoquinone, hydroquinone, p-benzoquinone, phenol, fumaric acid, maleic acid, oxalic acid and formic acid as measured by high-performance liquid chromatograph (HPLC), gas chromatograph coupled with mass spectrophotometer (GC-MS) and ion chromatograph (IC) techniques. The decomposition mechanism of 4-nitrophenol was also discussed.