Factors affecting the efficiency of a photocatalyzed process in aqueous metal-oxide dispersions - Prospect of distinguishing between two kinetic models
Factors affecting the efficiency of a photocatalyzed process in aqueous metal-oxide dispersions - Prospect of distinguishing between two kinetic models
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DOI：
10.1016/s1010-6030(00)00225-2
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发表时间：
2000-05-08
影响因子：
4.3
通讯作者：
Serpone, N
中科院分区：
文献类型：
--
作者：
Emeline, AV;Ryabchuk, V;Serpone, N
重新审视了 TiO2 水分散体中苯酚的光氧化降解，以确定速率对苯酚浓度和 365 nm 光化光光子流 (rho) 的依赖性。主要目的是评估影响光催化过程效率的因素，其速率由函数 dC/dt(rho, C) = (const) C(n)rho(m) 描述，其中 n 和 m 分别是相对于浓度和光子流（光强度）的反应级数。反应级数 m 随试剂浓度 C 变化，而级数 n 取决于光子流 rho。描述表明，如果n --> 0，则m -- 1，而如果m --> 0，则n --> 1。因此，苯酚光降解的反应级数m 和n 是相互依赖的。基于两个众所周知的机械/动力学模型给出了该过程的详细动力学描述，即（i）Langmuir-Hinshelwood（ZH）模型，其中有机试剂在紫外线照射之前被预吸附在光催化剂表面上，以及（ii）Eley-Rideal（ER）模型，其中有机试剂从溶液体扩散到光催化剂表面，与光催化剂的活化态相互作用。动力学处理推断，可以（在某些条件下）根据非常高光子下的 Langmuir 常数 K-L 的大小，即当 rho-->无穷大时（对于 LH 路径，K-L-->K；对于 ER 模型 K-L-->0）以及过程对 rho 的 k(obs) 依赖性，来划分 LH 和 ER 机械模型。对于 ER 模型，kobs 在高光子流下与 p 成线性比例，而对于 LH 路径 k(obs)，显示出对 rho 的亚线性依赖性，并且在高光子流下趋于饱和。 (C) 2000 EIsevier Science S.A. 保留所有权利。
The photooxidative degradation of phenol in aqueous TiO2 dispersions has been revisited to determine the dependencies of the rate on the concentration of phenol and on the photon flow (rho) of the actinic light at 365 nm. The principal objective was to assess the factors that influence the efficiency of the photocatalytic process, the rate of which is described by the functiondC/dt(rho, C) = (const) C(n)rho(m)where n and m are orders of the reaction with respect to concentration and photon flow (light intensity), respectively. The reaction order m varies with reagent concentration C, whereas the order n depends on photon flow rho. The description indicates that m -- 1 if n --> 0, whereas n --> 1 if m --> 0. Therefore, the reaction orders m and n of phenol photodegradation are interdependent. A detailed kinetic description of the process is given based on two well-known mechanistic/kinetic models, namely (i) the Langmuir-Hinshelwood (ZH) model whereby the organic reagent is pre-adsorbed on the photocatalyst surface prior to UV illumination, and (ii) the Eley-Rideal (ER) model for which the organic reagent diffuses from the solution bulk onto the photocatalyst surface to interact with the activated state of the photocatalyst. The kinetic treatment infers that it is possible (under certain conditions) to delineate between the LH and ER mechanistic models on the basis of the magnitude of the Langmuir constant K-L at very high photon how i.e. when rho-->infinity (for the LH pathway, K-L-->K; for the ER model K-L-->0), and on the dependence of k(obs), of the process on rho. For the ER model, kobs scales linearly with p at high photon flow, whereas for the LH pathway k(obs), displays a sub-linear dependence on rho and tends toward saturation at high photon flow. (C) 2000 EIsevier Science S.A. All rights reserved.