Titanium dioxide photoinduced degradation of some pesticide/fungicide precursors |
| |
Authors: | Kuehr Ivana Núñez Oswaldo |
| |
Institution: | Laboratorio de Química Ambiental, Departamento de Procesos y sistemas, Universidad Simón Bolívar, Apartado Postal 89.000, Caracas, Venezuela. |
| |
Abstract: | Five-membered nitrogen heterocycles (pyrrole, imidazole and 1,2,4-triazole) have been degraded using titanium dioxide and simulated solar radiation at pH = 8. The degradations followed a simple Langmuir-Hinshelwood mechanism. Accordingly, the adsorption equilibrium constants K of the heterocycles on the titanium dioxide surface and the rate constants k of degradation of the heterocycle-catalyst adduct have been obtained experimentally. While the K values decrease with heterocycle pKa, the k values increase with increasing pKa. Therefore, apparently, the rate constant depends on the availability of the electron pair on nitrogen, but at the same time the electron pair repulsion induced by the negatively charged titanium dioxide surface at pH = 8 causes a reverse effect in the adsorption equilibrium constant. Only in the case of imidazole, where the adsorption equilibrium constant is low enough (K = 0.013 M(-1)), can the rate constant be approximated to a pseudo-first-order rate expression: k(obs) = Kk. In all other cases, k(obs) = Kk/(1 + K(heterocycle)). |
| |
Keywords: | photocatalysis pesticides fungicides pyrrole imidazole 1 2 4‐triazole Langmuir‐Hinshelwood titanium dioxide |
本文献已被 PubMed 等数据库收录! |
|