Title : Photo-oxidation of cyanide in aqueous solution under visible light using Fe-TiO2 synthesized from ilmenite
Cyanide is a highly toxic substance widely used in the gold mining. Heterogeneous photocatalysis with TiO2 is an attracted alternative to degrade contaminants in lesser toxic substances. TiO2 needs UV light to be active which is undesirable. However, when it is doped with iron can absorb visible light.
In this work were synthesized several powders type Fe-TiO2 with different content of iron (400FT75_0.03, 400FT75_0.08, 400FT85_3.7 and 400FT85_6.4). The powders were obtained from ilmenite originating of alluvial mining wastes using acid extraction under soft conditions. The materials synthesized were characterized by several technics. X-ray diffraction patterns (XRD) of TiO2 anatase used as reference and the synthesized materials confirm the anatase phase for all of the synthesized materials. The content of iron in the materials was determinated by X-ray fluorescence showing a different amount of Fe for each material (0.03, 0.08, 3.7 and 6.4 mol %). Sortometry analysis showed a higher specific surface area for all powders with respect to the reference anatase. The optical properties of synthesized powders were obtained using UV-Vis diffuse reflectance spectroscopy and the results exhibit a red shiftment and a decrease in the band gap energy due to the presence of Fe. The powders were evaluated in the photo-oxidation of 50 ppm of cyanide in aqueous solution. The reactions were conducted under visible light of low intensity (4 W) at room temperature during 4 hours. With the purpose of follow the reactions, aliquots of solution were taken from time to time, measuring the cyanide concentration by UV-Vis spectroscopy. The higher conversion of cyanide (47 %) was reached for the powder 400FT85_3.7 with 3.7 mol % of Fe, while the lower was obtained for the anatase used as reference (23 %). In conclusion, all the materials synthesized in this work had a higher specific surface area and a lower band gap energy and also were more active in the photocatalytic photo-oxidation of cyanide under visible illumination of low intensity with respect to pure anatase.
Audience Take Away:
- The audience will learn about the potential use of ilmenite originating from alluvial mining wastes for the synthesis of photocatalysts more actives in the visible light region than TiO2 in anatase phase.
- The use of wastes of alluvial mining for the synthesis of active materials, represents a value on the waste. Further, the fact that the experimental conditions employed are soft, could help to develop new designs to contribute to decreasing the environmental impact of toxic substances like cyanide.
- The process of synthesis of materials type Fe-TiO2 active in the visible region using ilmenite from alluvial gold wastes could be scaled and optimized, giving an added value on a mineral present in alluvial gold mining wastes. It could be elaborated a process for the production on Fe-TiO2 and to promote the remediation of waters contaminated with cyanide.