RESUMO
Catalysed degradation of aqueous solutions of cinnamic 1, dihydrocinnamic 2, dihydrocaffeic 3 and trans-caffeic 4 acids in the presence of (TiO2) and UV radiation and the products identified by HPLC, and after treatment with diazomethane by GC-MS have been studied. A pH range of 3 to 11 was used. The four acids, in the presence of TiO2 in the dark, underwent little degradation. Extended irradiation of all the acids in the presence of TiO2 produced complete degradation as shown by TOC measurements. Initially the volume of carbon dioxide produced rose steadily to a constant value.
Assuntos
Ácidos Cafeicos/química , Cinamatos/química , Catálise , Cromatografia Líquida de Alta Pressão , Cromatografia Gasosa-Espectrometria de Massas , Concentração de Íons de Hidrogênio , Resíduos Industriais , Oxidantes Fotoquímicos/química , Fotoquímica , Titânio/química , Eliminação de Resíduos Líquidos/métodos , Poluição da Água/prevenção & controleRESUMO
Quantitative studies of the catalysed degradation of aqueous solutions of cinnamic 1, dihydrocinnamic 2, trans-caffeic 3 and dihydrocaffeic 4 acids in the presence of TiO2 and UV radiation at pH 3 and 10 are reported. The phenolic and aliphatic unsaturated groups in caffeic acid 3 caused it to be adsorbed more strongly than the phenolic saturated acid 4, and these two acids were much more strongly adsorbed than cinnamic and hydrocinnamic acids. The kinetics of the degradation of each acid has been studied at pH 3 and 10. TIC analysis showed complete mineralisation of the acids after 9 h.
Assuntos
Cinamatos/química , Fenilpropionatos/química , Adsorção , Catálise , Poluentes Ambientais , Concentração de Íons de Hidrogênio , Cinética , FotoquímicaRESUMO
A photoreactor was developed to study products of photochemical oxidation in a wide range of organic compounds. Analysis of the products from the reactor were used to determine the extent of mineralization of the organic material, to characterize any intermediate compounds formed, and to obtain information on the decomposition mechanism. Appropriate methods for separation and characterization include LC, UV spectrophotometry, gas chromatography/mass spectrometry, total organic carbon, and total inorganic carbon. The uses of the reactor are described for the photocatalytic decomposition of phenol and of its major decomposition intermediates 1,2- and 1,4-dihydroxybenzene.
