Ixchel Alejandra Mejía Estrella

This work focuses on the synthesis and optimization of nanostructured platinum (Pt) catalysts supported on commercial titanium oxide and cerium oxide (TiO₂-CeO₂) composite for the photocatalytic degradation of herbicides in This preprint research paper has not been peer reviewed. Electronic copy available at: https://ssrn.com/abstract=5600301 P r e p r i n t n o t p e e r r e v i e w e d efficient charge transfer from the valence to the conduction band upon light absorption within the active spectral region. Textural and structural characterization further revealed enhanced photophysical properties, confirming the superior performance of the optimized catalyst. This innovative methodology successfully maximized the photocatalytic degradation of 2,4-D, achieving improved efficiency under visible light conditions. The integration of computational techniques in the catalyst development process not only enhanced the degradation efficiency but also provided a scalable approach for addressing environmental contamination in agricultural wastewater.

In this research, the abundance and physical and chemical characteristics of microplastics (MPs) in coastal sediments from three beaches of Puerto Vallarta in Mexico were investigated. The objective of characterizing and finding MPs in sand is to generate information that is useful to manage macroplastic waste, prevent its additional generation, and thus reduce environmental pollution and achieve sustainable development. The MPs were classified according to their physical characteristics such as color, size, and shape under a stereoscopic microscope, and their wear and surface were observed using a scanning electron microscope. The chemical composition of the most representative types of polymers were detected by Fourier-transform infrared spectroscopy. It can be observed that Los Muertos beach presents the highest number of MPs (97.5 particles/m²) followed by Boca de Tomates beach (69.75 particles/m²) and Oro beach (28.75 particles/m²). The differences found between the beaches are attributed to the tourist influx and proximity to the mouth of a river. In total, 37% of MPs were white, followed by 19% yellow, and 11% transparent. The shape distribution of microplastics of sizes < 5 mm and 1 mm was fragmented, the greatest abundance was microfibers, microfragments, and microfilms for MPs between <1 mm and 1 µm, and these corresponded to polyester, polyethylene, cellophane, and polystyrene, respectively.

Antecedentes. La producción de plástico se ha incrementado considerablemente en las últimas décadas, teniendo una producción en 2019 de 368 millones de toneladas, donde una cantidad considerable termina desechada en el medio ambiente, donde se desgasta y descompone en microplásticos. Objetivos. Cuantificar y caracterizar los microplásticos presentes en las playas del área de influencia del Parque Nacional Sistema Arrecifal Veracruzano (PNSAV). Métodos. Se realizó un muestreo mediante cuadrantes ubicados en playas localizadas en la costa de Veracruz: La Mancha, Chachalacas, Chalchihuecan, Antón Lizardo y el Sendero, en los municipios de Actopan, Úrsulo Galván, la Antigua y Alvarado, respectivamente. Las partículas de plástico se obtuvieron después del secado y tamizado de la arena y se cuantificaron y caracterizaron por espectroscopía y microscopia. Resultados. Se encontró un total de 180 piezas de plástico (4.5 piezas/m2 ) en la zona de influencia del PNSAV. Las playas del Sendero y Chachalacas presentaron la mayor cantidad de piezas de plástico. Del total de partículas en el sistema, el 92.35 % presentó forma irregular, las restantes fueron fibras, “pellets” y películas. Con respecto al tipo y dominancia de polímeros plásticos encontrados en las playas, los tres materiales principales fueron polietileno de alta y baja densidad (26.67 y 27.22 %, respectivamente) y polipropileno (23.33 %). Conclusiones. Se encontraron microplásticos en todas las playas analizadas, la mayor parte presentaron forma irregular. Los microplásticos representan un riesgo para los organismos que los ingieren, ya que se ha reportado que sirven como vectores de microorganismos patógenos y dispersores de sustancias químicas tóxicas.

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.