Photodegradation of Methylene Blue and Evans Blue by Iron and Sulphur Doped TiO2 Nanophotocatalyst under Ultraviolet and Visible Light Irradiation

Abstract

Abstract. This research firstly aims to fabricate and characterize doped TiO2 nanoparticles (NPs) by iron and Sulphur dopants, and then the determination of the photocatalytic activity of NPs. Titanium tetraisopropoxide (TTIP), iron trichloride hexahydrate, thiouria, glacial acetic are utilized as precursors in the hydrothermal method without using a template or surfactant. The synthesized NPs are investigated by X-ray diffraction (XRD), field emission electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), N2 adsorption-desorption, UV-Vis spectroscopy, UV-Vis diffuse reflectance spectroscopy (DRS) and Fourier transform infrared (FT-IR). The lattice constants, strain, stress, deformation energy density and crystallite size are investigated using Williamson-Hall (W-H) and Wagner-Halder (W-H) models by considering the different isotropic nature of the crystalline lattice. The X-ray analysis indicates the tetragonal anatase phase without dopant crystalline phases. The FE-SEM and TEM images reveal a granular shape of NPs with a mean diameter of about 35 nm. Decoloration or photodegradation of organic dyes such as methylene blue (MB) and Evans Blue (EV) under UV-Vis irradiation is a method to measure the photocatalytic activity of doped TiO2 NPs. The results indicate the significant effect of dopants on the photocatalytic activity of doped TiO2 NPs, so that in comparison with other studies, it has a higher performance and removal efficiency. The bandgap of NPs is estimated from the Kubelka-Munk theory to be 2.87 eV. 
 
 Resumen. Esta investigación tiene como objetivo fabricar y caracterizar nanopartículas de TiO2 (NP) dopadas con hierro y azufre, y la actividad fotocatalítica de las NP. El tetraisopropóxido de titanio (TTIP), el tricloruro de hierro hexahidratado, la tiouria, el acético glacial fueron los precursores en la síntesi según el método hidrotermal y no se utilizó una plantilla o tensioactivo. Las NP sintetizadas se caracterizaron por difracción de rayos X (XRD), microscopía electrónica de emisión de campo (FE-SEM), espectroscopía de rayos X de dispersión de energía (EDX), microscopía electrónica de transmisión (TEM), adsorción-desorción de N2, espectroscopías UV-Vis, de reflectancia difusa UV-Vis (DRS) e infrarroja por transformada de Fourier (FT-IR). Las constantes de red, deformación, tensión, densidad de energía de deformación y tamaño de cristal se investigan utilizando modelos de Williamson-Hall (W-H) y Wagner-Halder (W-H), considerando la diferente naturaleza isotrópica de la red cristalina. El análisis de difracción de rayos X indica la fase anatasa tetragonal sin fases cristalinas dopantes. Las imágenes FE-SEM y TEM revelan una forma granular de las NP, con un diámetro promedio de aproximadamente 35 nm. La decoloración o fotodegradación de tintes orgánicos como el azul de metileno (MB) y el azul de Evans (EV) bajo irradiación UV-Vis es un método para medir la actividad fotocatalítica de las NP de TiO2 dopadas. Los resultados indican un efecto significativo de los dopantes sobre la actividad fotocatalítica de las NP de TiO2 dopadas, que, en comparación con otros estudios, tiene un mayor rendimiento y eficiencia de eliminación. La bandgap de las NP se estimó en 2.87 eV, a partir de la teoría de Kubelka-Munk.

Titanium Dioxide Nanoparticles Doped with Iron for Water Treatment via Photocatalysis: A Review

“…Even minor amounts of iron (up to a molar ratio of Fe/Ti drastically reduced the band gap from the 3.2 eV of pure titania to approximately 2 eV [6]. These values make the catalyst active under visible radiation [40], and the tion in the band gap is due to the formation of the Fe-O-Ti bond in the crystal la TiO2 [51]. Beyond a molar ratio of Fe/Ti of 0.1, a stabilization of the band gap is observed a approximately 1.9-2.1 eV, approaching the band gap value of hematite.…”

“…Even minor amounts of iron (up to a molar ratio of Fe/Ti of 0.1) drastically reduced the band gap from the 3.2 eV of pure titania to approximately 2.1−2.5 eV [6]. These values make the catalyst active under visible radiation [40], and the reduction in the band gap is due to the formation of the Fe-O-Ti bond in the crystal lattice of TiO 2 [51].…”

“…These alterations concerning nanoparticle size, the anatase-to-rutile phase transition, bandgap, surface properties, etc., are often interrelated and can either enhance or diminish photocatalytic performance [37][38][39]. For instance, Fe 3+ cations are thought to act as scavengers for photogenerated electrons during the photocatalytic process in the titania structure [40]. However, discrepancies emerge concerning their impact on enhancing electron-hole recombination properties [23].…”

Enhancement of the photocatalytic activity of fabricated ZnS nanoparticles in the photodegradation of methylene blue

“…The preferred crystalline phase, lattice structure, morphology, and the size of the fabricated ZnS NPs could extend the optical band gap upon the maximum absorption wavelength 350 nm to enhance the electro-optic and photocatalytic properties [29,30]. The rate of photodegradation and oxidizing reactivity have been improved by increasing the maximum absorption wavelength to the visible region i.e., red shifting the optical absorption edge from UV to the visible region [31]. A group of capable photocatalysis is S-based, such as ZnS, CdS, etc, which can be considered a sulfide semiconductor that absorbs UV-vis photons over a wide range of wavelengths.…”