One of the key features of a nano catalyst for photocatalysis is the band gap, because, through its analysis, the potential of the catalyst can be determined. In this investigation, the impact on the band gap of different catalysts made by the sol–gel method, compared with TiO₂ P25 Sigma-Aldrich, showing the effect of using gold or ruthenium as a metal supported on TiO₂, with two different dosage percentages of 1 and 3 percent, was analysed. Additionally, two oxidation states of the catalyst, the reduced form and the oxidized form of the metal, were used to see the effect on the band gap. The experiments show that the gold addition has a higher beneficial effect on the band gap for the UV region (ultra violet region), and the ruthenium addition has a higher beneficial effect for the UV/visible region. The preferred oxidation state for the band gap was the oxidized state. The characterisation of the catalyst provided an insight into the relation between the band gap and the catalyst itself.

Zinc nitrate (ZnO_N) and zinc acetate (ZnO_A) were used as precursors for the synthesis of zinc oxide (ZnO) nanoparticles by the sol–gel method. The ZnO powder was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy, X-ray diffraction (UV–Vis DRS), Fourier transform infrared spectroscopy (FTIR), physisorption of nitrogen, and X-ray photoelectron spectroscopy (XPS). On the other hand, the photocatalytic activity of the samples was tested in the degradation of 2,4-Dichlorophenoxyacetic acid (2,4-D) and 2,4-Dichlorophenol (2,4-DCP) under UV-light irradiation. The ZnO_N and ZnO_A showed polycrystalline irregular structures and rod-like morphology with mean sizes of 40 and 99 nm, respectively. The precursor type influenced the bandgap, crystallite size, surface area, total pore volume, and pore diameter. The XPS results showed high contents of C and N in the ZnO samples, and as a consequence, the solids present remarkable differences in the C/N, O/C, and O/Zn atomic ratios, which significantly influenced the physicochemical characteristics. The ZnO_N and ZnO_A exhibit photocatalytic properties against 2,4-D (74.7 and 90.9%, respectively) and 2,4-DCP (78.4 and 86.7%, respectively) and better performance of ZnO_A. These results are promising and indicate the potential to use this material as a photocatalyst to degrade organic pesticides.

Pure TiO₂ synthesized by the sol-gel method and subsequently deposited at 5% by weight with Co, Cu, Fe, and Ni ions by the deposition–precipitation method was studied as photocatalysts. The nanomaterials were analyzed by SEM, TEM, UV-Vis DRS, DRX, Physisorption N₂, and XPS. The SEM and TEM images present a semi-spherical shape with small agglomerations of particles and average size between 63 and 65 nm. UV-Vis results show that a reduction below 3.2 eV exhibits a redshift displacement and increment in the optical absorption of the nanoparticles promoting the absorption in the UV-visible region. XRD spectra and analysis SAED suggest the characteristic anatase phase in TiO₂ and deposited materials according to JCPDS 21-1272. The specific surface area was calculated and the nanomaterial Ni/TiO₂ (21.3 m² g⁻¹) presents a slight increment when comparing to TiO₂ (20.37 m²g⁻¹). The information generated by the XPS spectra present the deposition of metallic ions on the support and the presence of different valence states for each photocatalyst. The photocatalytic activity was carried out in an aqueous solution with 80 mg L⁻¹ of 2,4-D or 2,4-DCP under UV light (285 nm) with 100 mg L⁻¹ of each photocatalysts for 360 min. The nanomaterial that presented the best efficiency was Ni/TiO₂, obtaining a degradation of 85.6% and 90.3% for 2,4-D and 2,4-DCP, respectively. Similarly, this material was the one that presented the highest mineralization, 68.3% and 86.5% for 2,4-D and 2,4-DCP, respectively. Photocatalytic reactions correspond to the pseudo-first-order Langmuir–Hinshelwood model.

The objective of this research was to perform characterization of Mexican diatomite through different techniques and to analyze its efficiency in the adsorption of ciprofloxacin present in synthetic water. Mexico has large deposits of diatomite land that have not been well characterized; characterization is important in order to increase the use of this biomaterial in more specialized applications, such as the adsorption of emerging pollutants. Some of the emerging contaminants found in wastewater and surface water are antibiotics, such as ciprofloxacin. With the characterization, it was confirmed that diatomite is a nanostructured material composed of silicon oxide. Different forms of diatoms were found as well, corresponding to the species Discostella, Amphipleura and Cymbopleura, which showed a porous structure on the order of 50–380 nm with a surface area of 27·51 m²/g. The variables that were used to corroborate the adsorption efficiency of ciprofloxacin onto diatomite were the concentration of ciprofloxacin and initial pH for a period of time of 12 h. In this research, the data suggest a good affinity between ciprofloxacin and the diatomite. The adsorption efficiency at pH 9 was between 18 and 34%, and in the case of pH 6, it was between 64 and 75%.

Contexto: En la actualidad la nanotecnología posee múltiples áreas de acción que, debido a su naturaleza, la misma puede instrumentarse con amplia versatilidad, dado que, gran cantidad de avances en nanotecnología basan sus estudios en cómo optimizar procesos cotidianos e industriales y en cómo favorecer al medio ambiente. Aunado a ello, la manipulación de la materia a este nivel permite crear soluciones con mayor proyección en impacto científico, social y económico. Para fines de esta investigación, se mostrarán resultados a nivel de laboratorio usando nanomateriales celulósicos para la adsorción de contaminantes emergentes tipo antibióticos. Método: Esta investigación se realizó a nivel de laboratorio, en donde se modificó por métodos químicos celulosa para obtener nanocelulosa por oxidación. Se realizó una caracterización de material obtenido por técnicas de espectroscopia y se evaluó la adsorción de contaminantes emergentes tipo antibiótico como la ciprofloxacina. Resultados: Los nanomateriales celulósicos tienen potencial para ser usados en tratamiento de agua terciario en la eliminación de contaminantes emergentes como la ciprofloxacina. Los resultados muestran que el nanomaterial celulósico adsorbe la ciprofloxacina en un 27 %. Conclusiones: Las membranas de nanocelulosa tienen potencial para ser usadas en un sistema de purificación de agua; aquellas echas solo con celulosa presentaron un menor porcentaje de adsorción del contaminante que las membranas con nanocelulosa.

Nanostructured catalysts of platinum (Pt) supported on commercial TiO₂, as well as TiO₂-CeO₂ (1, 5 and 10 wt% CeO₂), were synthesized through the Sol-Gel and impregnation method doped to 1 wt% of Platinum, in order to obtain a viable photocatalytic material able to oxidate organic pollutants under the visible light spectrum. The materials were characterized by different spectroscopy and surface techniques such as Specific surface area (BET), X-ray photoelectron spectroscopy (XPS), XRD, and TEM. The results showed an increase in the diameter of the pore as well as the superficial area of the supports as a function of the CeO₂ content. TEM images showed Pt nanoparticles ranking from 2–7 nm, a decrease in the particle size due to the increase of CeO₂. The XPS showed oxidized Pt²⁺ and reduced Pt⁰ species; also, the relative abundance of the elements Ce³⁺/Ce⁴⁻ and Ti⁴⁺ on the catalysts. Additionally, a shift in the Eg band gap energy (3.02–2.82 eV) was observed by UV–vis, proving the facticity of applying these materials in a photocatalytic reaction using visible light. Finally, all the synthesized materials were tested on their photocatalytic oxidation activity on a herbicide used worldwide; 2,4-Dichlorophenoxyacetic acid, frequently use in the agriculture in the state of Jalisco. The kinetics activity of each material was measured during 6 h of reaction at UV–Vis 190–400 nm, reaching a removal efficiency of 98% of the initial concentration of the pollutant in 6 h, compared to 32% using unmodified TiO₂ in 6 h.