In this research, the adsorption capacity of diatomaceous earth in the removal of the crystal violet dye (CV) in aqueous solution was evaluated. The experimental methodology began with the determination of the texture properties by adsorption-desorption isotherms with N2 a 77 K, the identification of functional groups by Fourier transform infrared spectrophotometry (FTIR), morphology by scanning electron microscopy (SEM) and, the pH of the isoelectric point by the point of zero charge (PZC). A categorical multifactorial design was developed with factors such as the initial concentration of the dye (300-1000 mg/dm3), the temperature (30, 35 and 40ºC) and the initial pH of the solution (5, 6, 7 and 8). The maximum adsorption capacity was of 96.1 mg/g up 30ºC and pH 8, satisfactorily fitting the experimental data to the Langmuir isotherm model with R2 = 0.99, suggesting a monolayer adsorption mechanism on a homogeneous surface. In conclusion, diatomaceous earth can be considered as an efficient adsorbent in the removal of CV in aqueous solution.

This work shows to the reader a general description about the techniques of classic thermal analysis as known as Differential Scanning Calorimetry (DSC), Differential Thermal Analysis (DTA) and Thermal Gravimetric Analysis. These techniques are very used in science and material technologies (metals, metals alloys, ceramics, glass, polymer, plastic and composites) with the purpose of characterizing precursors, following and control of process, adjustment of operation conditions, thermal treatment and verifying of quality parameters.

RESUMENLa contaminación del agua con colorantes sintéticos, resultado de las actividades industriales, es un problema latente en la sociedad. Su presencia, aun en concentraciones muy bajas, influye drásticamente en los procesos de fotosíntesis, porque impide la penetración de la luz, afectando la vida acuática e, incluso, la salud humana. La adsorción con carbón activado es una de las técnicas más empleadas para remover el color de los efluentes, pero sus altos costos han dirigido la atención de los investigadores hacia el estudio de materiales adsorbentes provenientes, principalmente, de la agroindustria. Este artículo presenta un estudio sobre la remoción del colorante azul directo 2 en disolución acuosa sobre borra de café sin tratar y modificada a 30±1°C, en una columna empacada. Se realizó la caracterización fisicoquímica de los adsorbentes, que incluye la evaluación de las propiedades de textura, mediante isotermas de adsorción, con N2 a 77K, la identificación y cuantificación de grupos funcionales orgánicos, con FTIR y el método de Boemh. El estudio en columna evaluó el efecto de la altura del lecho del adsorbente (Z = 3 y 6cm), el flujo volumétrico (Qv= 2 y 4cm 3 min -1

This article shows the trend in the development of solar thermal and solar photovoltaic technologies and their impact on developing more efficient and sustainable systems based on a bibliometric and scientometric study from 2000-2022. By conducting a bibliometric analysis, the incidence of publications related to the topic was determined, concerning the countries with the highest production, institutions, most representative authors, and keyword analysis, among others; in addition, the study of patents related to the topic was analyzed. The databases Scopus, Journal citation report, Espacenet software, and different computer tools were used for the analysis. The results showed that the countries with the most significant impact and production of technologies are the United States, India, China, Spain, and Brazil, which account for more than 50% of the total. The United States is the country that produces the most patents

The development of nanotechnology and nanomaterials has had an upward surge in recent years, not only because of the type of technology but also because of the unique properties and characteristics of nanomaterials. This growth motivated us to make an analysis of emerging technologies in the development of metallic, bimetallic, and metal-oxide nanoparticles covering a period of ten years, which have had a high impact on the development of different products applied to biomedicine, electronics, agriculture, energy, plastics, etc. This research found more than one and a half million scientific papers under the keyword ‘nanotechnology’ in the Scopus database. This article reports a scientometric analysis where aspects such as articles with the highest number of citations, countries with the highest production, representative institutions in the field, authors and the relation of citations, correlations between them, keyword analysis, as well as the most studied topics in this field were investigated. On the other hand, the number of patents produced was reviewed in a general way. The databases Scopus, Journal Citation Report, VOSviewer, and other computer tools were used for the analysis. The results showed the United States (17.3%) and China (15.3%) as the countries with the greatest impact on studying metallic and bimetallic nanoparticles, with a high correlation between different countries. It is worth highlighting the participation of India with 10.1% and more than twice as many scientific papers as Germany; in the case of patents, the United States and China accounted for 55.3% of the total patents.