TiO_2光催化臭氧氧化降解全氟辛酸的研究

Efficient Degradation of Perfluoroocatanoic Acid by TiO_2-Mediated Photocatalytic Ozonation

TiO_2光催化臭氧氧化可以有效降解全氟辛酸(PFOA),反应4 h后的脱氟率达到44.3%.考察了PO_4^(3-)、PFOA初始浓度、反应温度对PFOA脱氟率的影响.结果表明,TiO_2光催化臭氧氧化降解PFOA过程发生在催化剂表面,PFOA和O_3在TiO_2表面的吸附是降解反应发生的必要条件;反应过程的前半段温度占主导因素,脱氟率随温度升高而升高,反应过程的后半段吸附作用影响更大,温度越低脱氟率反而越高;降解过程中产生的中间产物主要是5种短链全氟羧酸化合物,包括C_6F_(13)C_OOH、C_5F_(11)C_OOH、C_4F_9C_OOH、C_3F_7C_OOH和C_2F_5C_OOH.TiO_2光催化臭氧氧化降解PFOA的机理类似于Photo-Kolbe反应.

Perfluoroocatanoic acid（ PFOA） could be efficiently degraded by the combined process of photocatalysis and ozonation. After 4 h reaction,its defluorinaton ratio reached to 44. 3%. The effects of PO_4^（3-）,initial concentration and reaction temperature on the defluorination were investigated. The results showed that the process of TiO_2-mediated photocatalytic ozonation of PFOA was taken place on the surface of catalyst,the adsorption of PFOA and O_3 on TiO_2 surface was the primary condition of reaction. The reaction temperature was the dominant factor in the first half of reaction process,defluorination increased with increasing temperature. While adsorption replaced the position of reaction temperature on the terminal of reaction process,defluorination decreased with increasing temperature. The degradation intermediates were fluoride ions and short-chain perfluorocarboxylic acids（ PFCAs） including C_6F_（13） C_OOH,C_5F_（11）C_OOH,C_4F_9 C_OOH,C_3F_7C_OOH and C_2F_5 C_OOH. The degradation mechanism of PFOA by photocatalytic ozonation was proposed and found to be similar to Photo-Kolbe reaction.