(606f) Titanium-Loaded Photocatalytsts for Removal of Organic Dyes From Wastewater Using Visible Light Irradiation

Heterogeneous photocatalytic oxidation (HPO) processes employing catalysts
such as TiO₂, ZnO, etc., using UV light
has shown promising results for the degradation of persistent organic
pollutants, and their conversion to more biologically degradable and less toxic
substances. However, a large number of organic contaminants cannot be fully
degraded by such methods. In order to meet increasingly more stringent
environmental regulations and laws, more efficient processes for the removal of
organic pollutants are needed. Among the most promising and advanced methods
being investigated, photocatalysis at semiconductors
and at TiO₂, in particular, receives a considerable attention as
reflected by the recent large body of research published in this field.
Titanium dioxide, however, can be easily degraded when subjected to the
relatively harsh UV irradiation. Moreover, use of UV irradiation is not
attractive in a large industrial scale water treatment processes because of its
potential harmful effects on humans. Both of the problems cited above could be resolved
if UV irradiation could be replaced by a harmless visible light irradiation.

Titanium dioxide
nanoparticles successfully anchored into 3-D mesoporous material (TUD-1) using
a sol-gel preparation strategy were prepared and tested as photocatalysts,
employing only visible light (λ = 447 nm), for the treatment of
wastewaters containing azo dyes. Samples of different
Si/Ti ratio, ∞, 100, 75, 50 and 25 and 10 w/w were prepared and
characterized by X-ray diffraction (XRD), transmission electron microscopy
(TEM), ultraviolet spectroscopy (UV), and nitrogen adsorption at 77K. The newly developed Ti-TUD-1 photocatalysts showed excellent activity towards the
removal of the tested Azo dyes solutions. Up to 98%
of azodyes were successfully removed from the
contaminated wastewater. Moreover, the catalysts showed remarkable stability
under the relatively mild irradiation conditions used. Repeated photodegradation tests demonstrated remarkable
reproducibility and showed no decrease in photocatalytic
activity after 5 cycles.