采用纳米TiO2(P25)粉末作为催化剂,研究了几种典型硝基取代酚在TiO2/UV悬浮体系下的光催化降解。研究表明,这些化合物的降解过程符合Langmuir—Hinshelwood动力学方程,其表观速率常数(kapp)的大小为:2-氨基4硝基酚(2-A,4-NP)〉4-硝基酚(4-NP)〉2-硝基酚(2-NP)〉3-硝基酚(3-NP)〉2,4-二硝基酚(2,4-DNP)〉2,4,6-三硝基酚(2,4,6-TNP),而吸附平衡常数(KL)却与kapp成反比。苯环上取代基的种类和数目对有机物光催化降解活性有很大的影响,硝基的加入降低了光催化活性,并且kapp与Hammett常数(σ)具有较好的线性关系。
The photocatalytic degradation of nitrophenols in TiO2/UV suspension system was studied. The results show that the degradation kinetics can be described by Langmuir-Hinshelwood expression, and the apparent rate constants (kapp) are in the order : 2-A,4-NP 〉 4-NP 〉 2-NP 〉 3-NP 〉 2,4-DNP 〉 2,4,6-TNP. Whereas the adsorption equilibrium constants (KL ) are in inverse proportion to the apparent rate constants (kapp). The substituents on the aromatic ring significantly influence the photocatalytic activity, the addition of the nitro group will lead to the decrease of reactivity, and the kapp values show a good linear relationship with Hammett constants (σ).