In this study, the synthesis of ordered macroporous catalysts (TiO₂, TiO₂/SiO₂ mixtures) was investigated. The ordered macroporous catalysts were used for the photocatalytic oxidation to decompose 4-chlorophenol which is non-biodegradable....[ Read more ]

In this study, the synthesis of ordered macroporous catalysts (TiO₂, TiO₂/SiO₂ mixtures) was investigated. The ordered macroporous catalysts were used for the photocatalytic oxidation to decompose 4-chlorophenol which is non-biodegradable.

The ordered macroporous catalysts were successfully made after the investigations of the effects of some facts on the synthesis of the catalysts. The factors were the particle size of templates, the calcined temperatures, and composition of the precursors used. For the synthesized catalysts, they had different properties, such as BET surface area, particle size distribution, crystalline phases (anatase and rutile) and optical property – reflectance of UV light by comparing with that of P25.

The macroporous catalysts were evaluated by the photocatalytic oxidations of 4-chlorophenol under the same conditions. The results were compared with that of P25. It is found that the degradation rates of 4-chlorophenol of using the macroporous catalysts were faster than that of using P25. However, the degradation rates of TOC of using the macroporous catalysts were slower than that of using P25. There were two reasons. One was that the macroporous catalysts were effective to decompose 4-chlorophenol, but ineffective to decompose the intermediates. The other reason was that the UV-A transmissions of the macroporous catalysts were higher than that of P25. So part of the UV-A was transmitted out of the reactor and could not be used by the catalysts. Further investigation is necessary to improve the degradation of TOC for the photocatalytic oxidation of 4-chlorophenol.

In addition, investigation of the intermediates of formed of the primary steps from the degradation of 4-chlorophenol by the macroporous catalysts was carried out by using HPLC/MS. 4-chlorocatechol and catechol were identified. These two intermediates were also found in the reaction with P25. However, hydroquinone and benzoquinone were not found in all of the reactions.