Oscar M. Gonzalez-Diaz

TiO2 activation by using activated carbon as a support: Part I. Surface characterisation and decantability study

In the present work, the effect of mixing TiO2 with different portions of activated carbon (AC) has been studied. Transmission electron microscopy (TEM), scanning electron micrograph (SEM), laser scattering, FTIR and UV spectrophotometric analysis have shown changes of some of the TiO2 physico-chemical characteristics in catalysts containing an AC concentration lower than 15% in weight. Changes in the catalyst colour, the vibration bands of the hydroxylic groups from FTIR studies and the UV absorption spectrum have been observed. It seems that these changes correspond with TiO2 acid–base changes. SEM and TEM studies show a perfect TiO2 particles distribution on the AC surface in catalysts with lower AC contents, that also yields a homogeneous particle size distribution. One of the most interesting features of the resulting catalysts is their fast decantability in comparison with that of TiO2. This way one of the most important drawbacks of photocatalysis, the catalyst separation from the solution, may be overcome. The present study shows that the AC not only exerts a synergistic effect when is combined with TiO2 as some authors suggest, but it also modifies the catalyst characteristics.

TiO2 activation by using activated carbon as a support: Part II. Photoreactivity and FTIR study

Abstract It has been demonstrated that the modification of the TiO2 acid–base properties by the presence of activated carbon (AC) considerably modify the interaction of some molecules with the catalyst surface and hence its photocatalytic characteristics. FTIR studies have shown that while phenol interacts with TiO2 yielding a phenoxide, in the catalyst low AC containing catalysts mixtures the surfacial hydroxylic groups are inserted in the aromatic ring in the symmetric position to the –OH group. Additionally, the 4-aminophenol study shows that the molecule interacts with the TiO2 surface by means of the amino group, while in the catalyst containing AC the interaction takes place through the hydroxylic group. These results have confirmed the catalyst acid–base properties changes determined by the characterisation studies already performed. Also, it has been observed that catalysts with the lowest AC content show better catalytic behaviour than the untreated TiO2 and those with higher AC load. Another interesting result is the efficiency of these catalysts under solar irradiation.