Nanoparticulate double-heterojunction photocatalysts comprising TiO_2(Anatase)/WO₃/TiO_2(Rutile) were produced by a sol–gel method. The resulting photocatalysts exhibit clear synergistic effects when tested toward the degradation of methyl orange under both UV and visible light. Kinetic studies indicate that the degradation rate on the best double-heterojunction photocatalyst (10 wt % WO₃-TiO₂) depends mainly on the amount of dye concentration, contrary to pure oxides in which the degradation rate is limited by diffusion-controlled processes. The synergistic effects were confirmed through systematic and careful studies including holes and OH radical formation, X-ray diffraction, electron microscopy, elemental analysis, UV–vis diffuse reflectance spectroscopy, and surface area analysis. Our results indicate that the successful formation of a double heterojunction in the TiO_2(Anatase)/WO₃/TiO_2(Rutile) system leads to enhanced photoactivity when compared to individual oxides and commercial TiO₂ P25.

The present investigation is focused on the preparation, characterization, and photocatalytic activity evaluation of TiO₂/zeolite, WO₃/zeolite, WO₃/TiO₂/zeolite, and WO₃/TiO₂ composites. Zeolite fujasite (FAU) was synthesized by the hydrothermal method, while the semiconductor/zeolite composites by a straightforward physical mixture and calcination treatment. The photocatalytic activity of the materials was evaluated through the methyl orange (MO) degradation under near-UV irradiation (365 nm). The photocatalysts were characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), Energy-dispersive X-ray Spectroscopy (EDX), UV–vis diffuse reflectance spectroscopy and nitrogen physisorption. Results indicated that TiO₂, WO₃, and Zeolite Y kept their crystalline phases after the preparation method. TiO₂ and WO₃ particles were distributed on zeolite surface. Also, no significant changes in the band gap energies of the photocatalysts were found. The surface area of zeolite FAU decreased with the addition of TiO₂ and WO₃. The best MO degradation under near-UV irradiation was obtained with WO₃/TiO₂ heterojunction and TiO₂ P25, no synergistic effect was found between semiconductors and zeolite FAU. Additionally, the kinetic data of the photocatalytic elimination of MO with all photocatalysts under near-UV radiation was investigated with several models: Zero-order, First-Order, Second Order, Modified Freundlich and Parabolic Diffusion, they were consistent with Modified Freundlich model. The effect of initial pH and photocatalyst weight was explored for TiO₂/Zeolite composite and it was found that the best MO degradation was obtained at natural pH of 10.3 and 0.2 g of composite was the optimal amount of photocatalyst. Finally, the positive hole formation in all photocatalysts was detected by UV–vis spectroscopy and it was discovered that the highest density of positive holes was obtained with TiO₂/zeolite composite.

Forming heterojunctions by coupling two or more semiconductors is an important strategy to develop stable and efficient photocatalysts able to operate both under near-UV and visible light. Five novel heterojunction systems were synthesized in the present study, using a modified sol-gel method: Bi2Mo3O12/TiO2, ZnFe2O4/TiO2, FeTiO3/TiO2, WO3(US)/TiO2 and WO3/TiO2. These heterojunction semiconductors were characterized by using XRD, SEM and EDX, UV-Vis diffuse reflectance spectroscopy and BET. Their photocatalytic activities were evaluated using methyl orange (MO) degradation under both near-UV and visible light. From the various heterojunctions developed, the WO3(US)/TiO(2 )photocatalyst was the one that showed the highest photocatalytic efficiency with this being assigned to the formation of a double heterojunction involving anatase, rutile and monoclinic WO3 phases. On this basis, a photocatalyst activation mechanism applicable to near-UV and visible light irradiation was proposed. This mechanism explains how the photogenerated electrons (e(-)) and positive holes (h(+)) can be transferred to the various phases. As a result, and given the reduced holes and electron recombination surface, hydroxyl radicals found were more abundant. To confirm this assumption, hole formation in the valence band was studied, using hole-scavenging reactions involving ion iodine (I-), while hydroxyl radical production used fluorescence spectroscopy.

Novel ternary photocatalyst TiO₂-ZnO/g-C₃N₄ was synthesized via a ball milling-assisted sol-gel method and its photocatalytic performance was tasted in photocatalytic degradation of methyl orange (MO) and metoprolol (MTP) under UV and Visible light. The samples were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), UV-visible diffuse reflectance spectroscopy (UV-Vis DRS), scanning electron microscopy (SEM), and nitrogen physisorption. Optical measurements confirmed that the combination of TiO₂, ZnO, and g-C₃N₄ extended the visible light absorption to 2.63 eV. SEM and FTIR revealed correct coupling between the three semiconductors, and hole density analysis suggested a synergistic effect reducing charge recombination. Additionally, reuse tests demonstrated the chemical stability of the material. In terms of pollutant degradation, the TiO₂-ZnO/g-C₃N₄ composite efficiently removed 97.75% of MO under UV-LED light and 98.57% under visible light in 300 minutes. Similarly, MTP degradation test reached 86.42% and 86.08% under UV-LED and visible light, respectively, after 300 minutes. These results highlight the material's potential for environmental applications, particularly in contaminant removal through photocatalysis.

En la región que comprende el acuífero Calera, Zacatecas, la producción intensiva del cultivo de chile (Capsicum ssp.) es de suma importancia económica, y depende totalmente del agua subterránea de un acuífero sobreexplotado en una zona cárstica y semiárida, la disponibilidad de agua se torna más limitada y la calidad del agua es de relevancia. El objetivo de la investigación fue evaluar el impacto a la calidad química del agua y determinar su aptitud para uso agrícola mediante los criterios de salinidad, sodicidad y toxicidad. Durante dos ciclos consecutivos se realizó un muestreo según la norma NOM-014-SSA1-1993 a los pozos que frecuentemente se usan para irrigación de chile. De acuerdo a la profundidad resultaron cinco estratos que van de 50 a 280 m sobre el nivel estático. Para los tres criterios se determinaron los parámetros de calidad de agua, su clasificación se mostró en un diagrama de Richards y su hidrogeoquímica mediante un diagrama de Piper. Se realizó un análisis de bloques completos al azar, un análisis de componentes principales y un clúster para identificar los parámetros que inciden considerablemente en la calidad del agua. Los resultados evidenciaron que el cultivo de chile no ha impactado la calidad del agua de acuífero y que la profundidad de los pozos no influye en ésta, más bien depende de la región en donde se ubica cada pozo, procesos de recarga, geología de la región, velocidad de las corrientes subterráneas y la infiltración por la acción de fallas y fracturas geológicas.

Novel ternary photocatalyst TiO ₂ -ZnO/g-C ₃ N ₄ was synthesized via a ball milling-assisted sol-gel method and its photocatalytic performance was tested in the photocatalytic degradation of methyl orange (MO) and metoprolol (MTP) under UV-LED and visible light. The samples were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen physisorption (BET), UV-visible diffuse reflectance spectroscopy (UV–Vis DRS), X-ray photoelectron spectroscopy (XPS) and positive hole production. Optical measurements confirmed that the combination of TiO ₂ , ZnO, and g-C ₃ N ₄ extended the visible light absorption to 2.63 eV. SEM, TEM, FTIR and XPS revelated correct coupling between the three semiconductors, and hole density analysis suggested a synergistic effect, reducing the charge recombination. Additionally, reusability tests demonstrated the chemical stability of the material. In terms of pollutant degradation, the TiO ₂ -ZnO/g-C ₃ N ₄ composite efficiently removed 97.75 % of MO under UV-LED light and 98.57 % under visible light in 180 min. Similarly, MTP degradation test reached 86.42 % and 86.08 % under UV-LED and visible light, respectively, after 180 min. These results highlight the mate-rial’s potential for environmental applications, particularly in contaminant removal through photocatalysis.