Wide angle X ray diffraction WAXD patterns
For the removal of dyes, conventional chemical and biological treatments have been applied but these processes are rather ineffective. In this context, one possible solution could be an adsorption treatment over biodegradable materials  and  since it is economically feasible  with respect to the most commonly used adsorbent such as activated carbon .
Also if the adsorption leads to the removal of dyes from wastewater, when the saturated adsorbent material is dumped into the land, it pollutes again the air and soil creating secondary pollution.
As promising alternative, heterogeneous photocatalysis using semiconductors could be used for wastewater treatment because it leads to the complete mineralization or detoxification of dyes to environmental benign CO2, H2O, nitrates, etc.
The low cost of catalysts and the utilization of renewable PD123319 associated to this technology, are attractive compared to other techniques .
Titanium dioxide (TiO2) is the photocatalyst widely used in water purification technology , , ,  and . However, the main deficiency for the practical applications of TiO2 is limited by its large band-gap (3.2 eV), meaning that it can be only active under the UV light irradiation , , , ,  and . The main research objectives are to increase the photocatalytic performances of TiO2 through the doping of its crystalline structure with non-metal ions that reduces the band-gap and makes possible the fruitful absorption of the visible light , , , , , , , , ,  and . It was shown that the doping of TiO2 with nitrogen has led to an enhanced photocatalytic activity in presence of visible light irradiation  and .