Degradación del colorante naranja II, utilizando ciclodextrinas soportadas en nanomateriales
Authors:   , Bazán Medina Agni Yair 
Published: April 2022

Water pollution is one of the most important problems in our days, the wastewater discharged by the textile industry exemplifies this problem because high concentrations of colorants and other organic compounds (additives, surfactants, etc.) have been reported from of this sector in aquatic ecosystems. The colorants in water bodies are slowly degraded, generating byproducts of greater toxicity that are easily bioaccumulative, consequently dissolved oxygen is reduced, and biogeochemical cycles are altered, affecting organisms at different trophic levels. On the other hand, technologies have been studied for the removal and degradations of dyes, among which electrochemical, biological (activated sludge), physicochemical (adsorption, coagulation/flocculation) treatments and advanced oxidation processes (POA) such as oxidation Fenton, ozonation and photocatalysis. However, solar photocatalysis has been of interest in recent years due to the promotion of reactions in the visible spectrum capable of favoring the degradation of dyes in relatively short times (60-180 min on average), thus avoiding the formation of more toxic by-products and, when the right catalysts are used, these can be recovered and used continuously. In this work, the synthesis method was developed to obtain a photocatalyst with a paramagnetic center of magnetite (Fe₃O₄), covered with titanium dioxide (TiO₂) and finally with a layer of β-cyclodextrin (β-CD). Each component was evaluated by stages, to determine in which stage a better photocatalytic degradation of the orange II dye was obtained from a synthetic effluent, which was exposed to direct sunlight for a maximum period of 180 minutes. The results obtained from the photocatalytic evaluation of Fe₃O₄ and the Fe₃O₄/TiO₂ and Fe₃O₄/TiO₂-βCD complexes indicated that Fe₃O₄ is the material that degrades in the highest percentage to the orange II azo dye, under a process of exposure to natural sunlight, in addition to showing adequate recoverability and reuse efficiency. Fe₃O₄ was synthesized by a simple precipitation technique, shows a particle size of 100.617 ± 42.043 nm, a surface charge of -12.133 ± 0.32 mV, a reflectance of 48.218 ± 0.258% at 900 nm wavelength and an bandgap energy (Eg) of 2.95 eV. The parameters of pH, catalyst concentration and exposure time where the greatest degradation occurs were found, these being: pH 2, a concentration of 50 mg/L of the photocatalytic complex, 180 μL of H₂O₂ and a time of exposure to sunlight of 60 minutes in the spring-summer (P-V) period to obtain a degradation percentage of 96.543 ± 0.504% and 90 minutes of exposure to sunlight in the autumn-winter (O-I) period to obtain a degradation percentage of 96.471 ± 0.070%. The experiments related to the reuse of Fe₃O₄ for 5 cycles indicated that it maintained adequate efficiency, since the degradation percentages remained above 90% for up to three consecutive cycles. However, for the fourth and fifth cycles, the percentages of degradation obtained were lower, these being 86.925 ± 0.407% and 78.119 ± 1.770%, respectively. Thanks to its paramagnetic properties, the easy recovery through the use of a magnet and the degradation percentages obtained, the synthesized Fe₃O₄ proves to be an alternative for the environmental restoration of contaminated water, this textile dye in areas with optimal solar radiation conditions.