Ultrafine multifunctional material based on a pigment with potential as a photocatalyst at dye degradation in an alkaline aqueous medium

Full text: An inorganic ultrafine-powder with commercial use directed as a green pigment was characterized in a structural way and its potential as Photocatalyst material was investigated. The powder exhibits an intense green color. Structural characterization was carried out via X-ray diffraction and Infrared Spectroscopy, while the potential photocatalytic of inorganic powder pigment was investigated in the degradation of phenol-red dye under both visible-light and UV-light. The infrared spectrum of the Green-pigment showed a set of well-shaped and intense absorption bands characteristics of H₂O, hydroxyl groups, carbonate groups and Fe bonded. X ray analysis showed that the green pigment is formed of a mixture containing as major phase an Iron oxyhydroxide carbonate called typically of Green-rust that exhibits a high crystallinity degree. The potential of this green pigment as photocatalyst was studied in homemade photocatalytic reactor using both low intensity visible-light and UV light. For degradation analysis an aqueous solution of phenol-red dye with concentration equal to 12.5 mg/L was prepared. The mass of the green pigment was varied from 100 to 500 mg. The whole process it occurred isolated from light in a period of 5 hours, 1 hour to establish adsorption/desorption equilibrium (lamp off) and 4 hours to the photocatalytic process. The aliquots were taken away periodically and measured in a single beam spectrophotometer in the wavelengths 430 nm. Green pigment was not active under visible light. In addition, a significant activity at dye degradation was monitored under the UV radiation. The level, rate and kinetic of degradation are discussed. (author)