臭氧光催化降解水中甲醛的研究

Research on degradation of formaldehyde in aqueous solution by combined photocatalysis and ozonation

研究比较了3种光化学方法对水中低浓度甲醛的降解效果,考察了初始pH值、甲醛浓度和臭氧投加速率等因素对臭氧光催化(TiO_2/UV/O_3)降解甲醛的影响。结果表明,紫外臭氧(UV/O_3)、光催化(TiO_2/UV)和TiO_2/UV/O_3对甲醛的降解均符合表观一级反应动力学,TiO_2/UV/O_3降解甲醛的一级表观速率常数大于TiO_2/UV与UV/O_3之和,说明臭氧、光催化有明显的协同作用。pH值对臭氧光催化降解甲醛的速率几乎没有影响;甲醛初始浓度增加,表观反应速率常数下降,但甲醛的绝对去除量仍随初始浓度的增加而显著增加;臭氧投加速率增加,降解速率增加。甲醛降解的主要中间产物为甲酸,但甲酸在臭氧光催化反应过程中也快速降解而被矿化,说明臭氧光催化是一种能安全有效去除甲醛的方法。

The degradation effects of low concentration formaldehyde in aqueous solution by three photochemical methods（UV/O3 ,TiO2/UV ,TiO2/UV/O3） were compared, and the effects of initial pH, formaldehyde concentration and ozone addition rate on the formaldehyde degradation by TiO2/UV/O3were studied. The results show that the degradations of formaldehyde in the three proeesses-UV/O3 TiO2/UV,TiO2/UV/O3, follow the apparent first-order reaction kinetics. The rate constant of TiO2/UV/O3 is larger than sum of those of TiO2/UV and UV/O3 , which indicates a synergistic effect of photocatalysis and ozonation. The effect of pH on formaldehyde degradation by TiO2/UV/O3 can be ignored. The rate constant decreases with the increase of initial concentration of formaldehyde, while the absolute removal amount of formaldehyde increases with the increase of its initial concentration. The rate constant increases with the increase of ozone addition rate. Formic acid is identified as the main intermediate product during formaldehyde degradation; however, formic acid is quickly degraded and mineralized during the reaction, indicating that TiO2/UV/O3 is a safe and effective method to remove formaldehyde.