Adsorption mechanism of acid orange 7 on photocatalytic materials based on TiO 2
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.481
Adsorption mechanism of acid orange 7 on photocatalytic materials based on TiO2 A. Arteaga-Jiménez1, A. I. Caudana-Campos1, A. L. García-García1, E. Hernández-Zapata2, M. A. Vidales-Hurtado1 1
Instituto Politécnico Nacional, CICATA Querétaro
2
Dpto. De Recursos de la Tierra, Universidad Autónoma Metropolitana, unidad Lerma
ABSTRACT The degradation of organic molecules in an aqueous medium using heterogeneous photocatalysis depends on the chemical composition and concentration of the organic compound, the crystalline and morphological nature of the photocatalyst, the pH of the dye dilution, and the reaction temperature. Since photocatalytic degradation is a process that occurs on the surface of the catalytic material, it is desirable to induce maximum adsorption of the organic compound. One strategy to achieve this is to functionalize the surface of the catalyst to retain the molecule of interest. In this work, we studied the interaction of acid orange 7 (AO7) with commercial TiO2-anatase powder catalyst, and with a catalyst synthesized in house using titanium tetrachloride and ethanolamine (TiO 2-et). Our results indicate that there is no adsorption of the AO7 dye on the TiO2-et particles. The infrared spectrum of the TiO2-et particles is presented.
INTRODUCTION Titanium dioxide, TiO2, is the main photocatalyst used to purify water and air. It is a low-cost, photostable material with a strong oxidizing power and antibacterial effect [1-3]. The mechanism to remediate organic molecules employing TiO 2 consists in photoactivation with 3.2 eV energy. The light excites the electrons causing them to pass from the valence band to the conduction band, forming a vacancy or hole in the titanium dioxide. If the photocatalyst is submerged in an aqueous solution, water molecules provide electrons to fill in the vacancies in the material. An electron is taken from one of the hydrogen atoms staying as a cation. The other hydrogen atom is neutral as is the oxygen atom, forming a hydroxil radical, *OH. The formation of the *OH radical is important for the remediation process because it can react with organic pollutants leading 3399
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to their mineralization; hydroxil groups are the most effective species in oxidation processes [4]. Under this principle, TiO2 as a photocatalytic material has been used to degrade pathogens and algae in water, to destroy toxins, herbicides, pesticides, dyes and phenols [5-9]. To improve the photocatalytic efficiency of TiO 2, it has been proposed to modify its surface properties by depositing transition metals on its surface, doping it with ions, combining it with other oxides or adsorbent materials and functionalizing the surface of the particles. The idea behind making metal depositions on TiO 2 relies
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