Fe-TiO₂ WITH LOW QUANTITY OF IRON EXTRACTED FROM (ILMENITE) MINING WASTE TO THE PHOTOCATALYTIC DEGRADATION OF CYANIDE IN WATER

Nanoparticles of TiO₂ doped with low amount of Fe were synthesized from natural ilmenite obtained from alluvial gold mine wastes. The obtained TiO₂ were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), UV-Vis diffuse reflectance, thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), N₂ adsorption-desorption isotherms, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results confirm the formation of mesoporous TiO₂ nanoparticles in anatase phase with 0.05 wt.% of iron possibly replacing some titanium places. All the characterizations were performed to the synthesized solid and the reference materials (TiO₂ anatase and Degussa P25). The photocatalytic activity of both the synthesized solid and references were evaluated in the photo-oxidation of cyanide in aqueous medium under UV illumination. An experimental design type Box-Behnken was performed choosing three different parameters: the initial concentration of cyanide (50, 150 and 250 ppm) the catalyst load (0.1, 0.5 and 1.0 g L^-1) and the oxygen source. The percentage of cyanide conversion was chosen as response in the design obtaining as optimal conditions [CN^-]₀ = 50 ppm, catalyst load = 0.6 g L^-1 and air bubbling. Under these conditions it was reached 32, 32 and 89% of cyanide conversion for Fe-TiO₂ synthesized, TiO₂ anatase and Degussa P25, respectively.

Keywords:
heterogeneous photocatalysis; titanium dioxide; cyanide; photodecomposition; ilmenite.