Use of novel cardanol-porphyrin hybrids and their TiO2-based composites for the photodegradation of 4-nitrophenol in water.

Cardanol, a well known hazardous byproduct of the cashew industry, has been used as starting material for the synthesis of useful differently substituted "cardanol-based" porphyrins and their zinc(II), copper(II), cobalt(II) and Fe(III) complexes. Novel composites prepared by impregnation of polycrystalline TiO2 powder with an opportune amount of "cardanol-based" porphyrins, which act as sensitizers for the improvement of the photo-catalytic activity of the bare TiO2, have been used in the photodegradation in water of 4-nitrophenol (4-NP), which is a toxic and bio-refractory pollutant, dangerous for ecosystems and human health.

Photocatalytic activity of nano and microcrystalline TiO(2) hybrid systems involving phthalocyanine or porphyrin sensitizers.

Hybrid photocatalysts based on TiO(2)-anatase matrix, representing the both micro- and nano-structures, impregnated with selected lanthanide diphthalocyanine and metalloporphyrin sensitizers, were compared to evaluate their activity and effectiveness in a water suspension catalytic system designed to degrade 4-nitrophenol (4-NP) in a UV-stimulated reaction. Either type of the anatase catalyst was proved to be effective in mineralizing of 4-NP. However, kinetic studies confirmed that the composite's efficiency basically depends on the nature of the macromolecular sensitizer and to a minor extent on the dimensions (micro/nano) of the TiO(2) particles. The apparent higher activity observed for the micro-TiO(2) catalysts indicates improvement of the electron transfer between the sensitizer and the micro-crystalline structure of TiO(2)-anatase in contrast to the nano-crystalline matrix. The mechanistic aspects of the observed catalytic performances have been discussed.

Degradation of 4-nitrophenol (4-NP) using Fe-TiO2 as a heterogeneous photo-Fenton catalyst.

Photocatalytic degradation of 4-nitrophenol was investigated using Fe-doped (1, 3, 5 and 8 wt.% Fe) TiO(2) catalysts under UV light irradiation in aqueous dispersions in the presence of H(2)O(2). Photocatalysts with the lowest Fe content (1%) showed a considerably better behavior with respect to the unloaded TiO(2) and the catalysts with higher Fe contents. Photocatalytic degradation was studied under different conditions such as amounts of 1% Fe-TiO(2) catalyst, H(2)O(2) dose and initial pH of 4-NP solution. The results indicated that about 67.53% total organic carbon of a solution containing 20 mg L(-1) 4-NP was removed at pH 6.17 by using 4.9 mM of H(2)O(2) and 0.4 g L(-1) of the catalyst in a 2-L batch photo-reactor, the complete degradation of 4-NP occurring after 60 min. It was also observed that catalytic behavior could be reproduced in consecutive experiments without a considerable decrease of the UV/Fe-TiO(2)/H(2)O(2) process efficiency.