Diatomite releases silica during spirit filtration

The purpose of this study was to ascertain whether diatomite is an inert filter aid during spirit filtration. Surely, any compound with a negative effect on the spirit composition or the consumer’s health could be dissolved. In this study different diatomites were treated with 36% vol. ethanol/water mixtures and the amounts and structures of the extracted compounds were determined. Furthermore, Brandy de Jerez was diatomite- and membrane-filtered at different temperatures and the silicon content was analysed. It was found that up to 0.36% by weight of diatomite dissolved in the aqueous ethanol and amorphous silica, in the form of hollow spherical microparticles, was the most abundant component. Silicon concentrations in Brandy de Jerez increased by up to 163.0% after contact with diatomite and these changes were more marked for calcined diatomite. In contrast, reductions of more than 30% in silicon concentrations were achieved after membrane filtration at low temperatures

Formation of siliceous sediments in brandy after diatomite filtration

Brandy is quite a stable spirit but sometimes light sediment appears. This sediment was separated and analysed by IR and SEM-EDX. It was revealed that the sediment is composed mostly of silica and residual organic matter. Silica was present as an amorphous phase and as microparticles. In an attempt to reproduce the formation of the sediment, a diatomite extract was prepared with an ethanol/water mixture (36% vol.) and a calcined diatomite similar to that used in brandy filtration. This extract was added to unfiltered brandy in different amounts. After 1 month, the Si concentration decreased in all samples and sediments with similar compositions and features to those found in the unstable brandy appeared. The amounts of sediment obtained were directly related to the decrease in Si concentration in solution. Consequently, it can be concluded that siliceous sediment in brandy originates from Si released during diatomite filtration

Dye decomposition and air de-pollution performance of TiO2/SiO2 and N-TiO2/SiO2 photocatalysts coated on Portland cement mortar substates

In this study, the newly synthesized TiO2 and N doped TiO2 clusters were added to silica sol to synthesize N-TiO2/SiO2 composites via the sol-gel method. Afterwards, the prepared cols were applied by brushing on portland cement. Doping with nitrogen significantly increased the absorption of TiO2 towards the visible region, thus, increasing the photocatalytic activity. SEM characterization of the treated samples showed that the clusters were distributed in form of aggregates on the samples' surface. The self-cleaning and air de-polluting performances were assessed through methylene blue degradation and the oxidation of nitrogen oxide, resulting in methylene blue (MB) removal of 85% and 78% after 60 min of irradiation for SN10TiO(2) and STiO2, respectively. Regarding air de-pollution performance, the newly synthesized photocatalysts showed the ability of NOx reduction. However, their efficiency was somewhat lower, in which 23.81% of NO has been oxidized by the sample SN10TiO(2), while SP25 showed a total NO conversion of 38.98%. The powdered xerogels of the newly synthesized nanoparticles revealed high photocatalytic efficiency concerning NO oxidation, resulting in a higher performance compared to those obtained by the xerogel containing P25Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This project has received funding from the European Union's Horizon 2020 Research and Innovation Framework Programme under grant agreement no 760858. This work has been financed by the Spanish State Research Agency R&D programme 2020 (Project reference: PID2020-115843RB-I00) and has been co-financed by the European Union under the 2014-2020 ERDF Operational Programme and by the Department of Economic Transformation, Industry, Knowledge, and Universities of the Regional Government of Andalusia (Project reference: FEDER-UCA18-106613). S. Khannyra would also like to thank the Aula del Estrecho of the University of Cadiz for her predoctoral grant

¿QUÉ ASPECTOS DE LA COMPETENCIA CIENTÍFICA EVALÚAN LAS PRUEBAS DE ACCESO A LA UNIVERSIDAD EN LA ASIGNATURA DE QUÍMICA? What aspects of the scientific competence are evaluated in entrance examinations to the University in the subject of Chemistry?

Se caracterizan las preguntas de la Prueba de Acceso a la Universidad en la asignatura de Química en las universidades andaluzas desde la perspectiva de sus demandas respecto a la competencia científica. Para ello se analizan 576 peguntas planteadas en el período 2002-2013, cuyos resultados indican sesgos y ausencias importantes para una evaluación integral de la competencia del alumnado en Química, sin apenas evolución con el tiempo. Es de destacar, en particular, una pobre presencia de aspectos experimentales de la química, relacionados con el diseño experimental y el trabajo práctico de laboratorio, y sobre todo una ausencia de preguntas que evalúen aspectos creativos y sobre la naturaleza de la química, o alrededor de problemas y situaciones de la vida cotidiana o de la dimensión tecnológica y ambiental. A partir del análisis se formulan implicaciones para la mejora de las pruebas externas selectivas y también para la formación del profesorado..AbstractFrom the point of view of the competences assessment, in this paper the Andalusian higher education access test in the subject of Chemistry is analysed. For this purpose, a content analysis was done, taking as reference 576 questions corresponding to the PAU questions raised between 2002 and 2013 in the Andalusian universities. The results indicate bias and important absences for a comprehensive assessment of the competence of students in chemistry, hardly any evolution over time. It is noteworthy, in particular, a poor presence of experimental aspects of chemistry, related to experimental design and practical laboratory work, and above all an absence of questions that assess creative aspects and about the nature of the chemistry or around its relations with problems and situations of daily life or the technological and environmental dimension. From the analysis implications for improving selective external testing and also for teacher training are formulated

Análisis de contenido de las pruebas de acceso a la universidad en la asignatura de Química en Andalucía

In this work, the test question typology to higher education access in chemistry subject has been studied. This study was performed in the autonomous community of Andalusia. According to curriculum topics and the category system proposed by Smith, Nakhleh y Bretz (2010) for chemistry exams, 576 questions were analyzed. The most frequent topics were stoichiometry, formulation and chemical nomenclature and acid-base equilibria, which accounted for about two thirds of the questions. The three categories of questions used were: definition, algorithmic and conceptual questions were used. It was observed a predominance of the algorithmic questions, although in recent years, some progresses of conceptual questions have been observed, but not statistically significant changes. A clear dependence between the type of question and the specific issue involved was observed. Therefore, questions about formulation were mostly included in the “definition” category, question about stoichiometry and thermodynamic in the “algorithmic” category and atom, periodic table and chemical bond questions were included in the conceptual category. From the data obtained, the need for a reorientation in the future of PAU tests is discussed.Se estudia la tipología de preguntas formuladas en las pruebas de Química de acceso a la universidad en la Comunidad Autónoma Andaluza. Se analizaron 576 preguntas según los temas del currículum implicados y de acuerdo al sistema de categorías propuesto por Smith, Nakhleh y Bretz (2010) para exámenes de Química. Los temas más frecuentes fueron los de estequiometría, formulación-nomenclatura química y equilibrio ácido-base, que conjuntamente acaparaban alrededor de dos tercios de las preguntas formuladas. Las tres categorías de preguntas empleadas fueron: de Definición, Algorítmicas y Conceptuales, predominando principalmente las segundas, aunque con un cierto avance en los últimos años de las de tipo Conceptual, aunque los cambios no resultaran estadísticamente significativos. Se observó una clara dependencia del tipo de preguntas de la temática concreta implicada en las mismas, siendo aquellas sobre formulación las que más se prestan a la categoría de “definición”, las de estequiometría y termoquímica a las “algorítmicas”, y las de átomo, Tabla periódica y enlace químico a las de tipo conceptual. A partir de los datos proporcionados se discute la necesidad de una reorientación de estas pruebas con vistas al futuro.Palabras clave: enseñanza de la química; pruebas externas; PAU; Pruebas de acceso a la universidad; Preguntas de examen.Type of test questions to higher education access in chemistry subjectIn this work, the test question typology to higher education access in chemistry subject has been studied. This study was performed in the autonomous community of Andalusia. According to curriculum topics and the category system proposed by Smith, Nakhleh y Bretz (2010) for chemistry exams, 576 questions were analyzed. The most frequent topics were stoichiometry, formulation and chemical nomenclature and acid-base equilibria, which accounted for about two thirds of the questions. The three categories of questions used were: definition, algorithmic and conceptual questions were used. It was observed a predominance of the algorithmic questions, although in recent years, some progresses of conceptual questions have been observed, but not statistically significant changes. A clear dependence between the type of question and the specific issue involved was observed. Therefore, questions about formulation were mostly included in the “definition” category, question about stoichiometry and thermodynamic in the “algorithmic” category and atom, periodic table and chemical bond questions were included in the conceptual category. From the data obtained, the need for a reorientation in the future of PAU tests is discussed.Keywords: chemical Education; College entrance exam; external testing, PAU; test questions

What aspects of the scientific competence are evaluated in entrance examinations to the university in the subject of Chemistry?

Se caracterizan las preguntas de la Prueba de Acceso a la Universidad en la asignatura de Química en las universidades andaluzas desde la perspectiva de sus demandas respecto a la competencia científica. Para ello se analizan 576 peguntas planteadas en el período 2002-2013, cuyos resultados indican sesgos y ausencias importantes para una evaluación integral de la competencia del alumnado en Química, sin apenas evolución con el tiempo. Es de destacar, en particular, una pobre presencia de aspectos experimentales de la química, relacionados con el diseño experimental y el trabajo práctico de laboratorio, y sobre todo una ausencia de preguntas que evalúen aspectos creativos y sobre la naturaleza de la química, o alrededor de problemas y situaciones de la vida cotidiana o de la dimensión tecnológica y ambiental. A partir del análisis se formulan implicaciones para la mejora de las pruebas externas selectivas y también para la formación del profesorado..From the point of view of the competences assessment, in this paper the Andalusian higher education access test in the subject of Chemistry is analysed. For this purpose, a content analysis was done, taking as reference 576 questions corresponding to the PAU questions raised between 2002 and 2013 in the Andalusian universities. The results indicate bias and important absences for a comprehensive assessment of the competence of students in chemistry, hardly any evolution over time. It is noteworthy, in particular, a poor presence of experimental aspects of chemistry, related to experimental design and practical laboratory work, and above all an absence of questions that assess creative aspects and about the nature of the chemistry or around its relations with problems and situations of daily life or the technological and environmental dimension. From the analysis implications for improving selective external testing and also for teacher training are formulated.peerReviewe

Type of test questions to higher education access in chemistry subject

Se estudia la tipología de preguntas formuladas en las pruebas de Química de acceso a la universidad en la Comunidad Autónoma Andaluza. Se analizaron 576 preguntas según los temas del currículum implicados y de acuerdo al sistema de categorías propuesto por Smith, Nakhleh y Bretz (2010) para exámenes de Química. Los temas más frecuentes fueron los de estequiometría, formulación-nomenclatura química y equilibrio ácido-base, que conjuntamente acaparaban alrededor de dos tercios de las preguntas formuladas. Las tres categorías de preguntas empleadas fueron: de Definición, Algorítmicas y Conceptuales, predominando principalmente las segundas, si bien con un cierto avance en los últimos años de las de tipo Conceptual aun cuando los cambios no resultaran estadísticamente significativos. Se observó una clara dependencia del tipo de preguntas de la temática concreta implicada en las mismas, siendo aquellas sobre formulación las que más se prestan a la categoría de “definición”, las de estequiometría y termoquímica a las “algorítmicas”, y las de átomo, Tabla periódica y enlace químico a las de tipo conceptual. A partir de los datos proporcionados se discute la necesidad de una reorientación de estas pruebas con vistas al futuro.In this work, the test question typology to higher education access in chemistry subject has been studied. This study was performed in the autonomous community of Andalusia. According to curriculum topics and the category system proposed by Smith, Nakhleh y Bretz (2010) for chemistry exams, 576 questions were analyzed. The most frequent topics were stoichiometry, formulation and chemical nomenclature and acid-base equilibria, which accounted for about two thirds of the questions. The three categories of questions used were: definition, algorithmic and conceptual questions were used. It was observed a predominance of the algorithmic questions, although in recent years, some progresses of conceptual questions have been observed, but not statistically significant changes. A clear dependence between the type of question and the specific issue involved was observed. Therefore, questions about formulation were mostly included in the “definition” category, question about stoichiometry and thermodynamic in the “algorithmic” category and atom, periodic table and chemical bond questions were included in the conceptual category. From the data obtained, the need for a reorientation in the future of PAU tests is discussed

Self-cleaning durability assessment of TiO2/SiO2 photocatalysts coated concrete: Effect of indoor and outdoor conditions on the photocatalytic activity

A self-cleaning nanostructured TiO2 coating has demonstrated the capacity to mitigate undesired effects from air pollution. Not only it reduces the deterioration of building materials but may also prevent certain pollution-related human health problems. In this study, mesoporous TiO2/SiO2 photocatalysts were synthesized in order to produce self-cleaning and long-lasting coatings that meet the necessary requirements for outdoor applications. The synthesized products were sprayed on concrete substrates and their self-cleaning and air depolluting capabilities were evaluated. The former one as a function of methylene blue (MB) and soot degradation and the latter, according to nitrogen oxides reduction. The coatings proved to have high photocatalytic activity, and their efficiency was enhanced as TiO2 loadings were increased. Thus, after the first 60 min of their irradiation by UV–vis light, the photocatalysts ST1 and S4T had removed 79% and 95% of the MB, respectively. These coatings presented particulate surfaces that provided more surface area and porosity, which are key factors for a high photocatalytic activity. Moreover, the same samples after 104 h of irradiation exhibited 38% and 49% conversion of total NO, respectively. While E503, a commercially available photocatalyst, produced coating cracked surfaces and a total MB degradation of just 50% after 60 min of irradiation as well as 35% of NO conversion after 104 h of irradiation. The TiO2/SiO2 coatings’ photocatalytic efficacy remained practically invariable after four months of exposure to real-life conditions and three MB degradation cycles. After the outdoor durability tests, the coated surfaces exhibited a practically unchanged structure, which confirms their long-lasting efficiency. © 2022 The AuthorsThis work has been supported by the Spanish Government MAT2017-84228-R (MINECO/AEI//FEDER, UE) and PID2020- 115843RB-I00/AEI/10.13039/501100011033 . This work has been co-financed by the European Union under the 2014–2020 ERDF Operational Programme and by the Department of Economic Transformation, Industry, Knowledge, and Universities of the Regional Government of Andalusia . Project reference: FEDER-UCA18-106613

Alkylsiloxane/alkoxysilane sols as hydrophobic treatments for concrete: A comparative study of bulk vs surface application

Water and waterborne decay agents (e.g. salts, microorganisms) are commonly associated with undesired alterations and damages on concrete elements. A strategy to mitigate their impact is to decrease water retention in the material either by surface treatments or admixtures. In this work, hydrophobic concretes were developed by the addition of a hydrophobic sol containing TEOS and PDMS oligomers, synthetized by a surfactant-assisted sol-gel route, either as an admixture or as a surface treatment. The hydrophobic performance was similar for both application modes (>70% capillary absorption reduction) and higher than concrete containing a commercial (calcium stearate) admixture or a nanosilica-based hydrophobic coating. Addition as an admixture led to a higher durability in the rain and abrasion tests. The hydrophobic sol as an admixture promotes an increase of surface roughness and porosity, as well as the formation of C–S–H like reaction products with the cement matrix components, as evidenced by AFM, MIP, SEM and FTIR. Despite the higher porosity, impact resistance and material cohesion were not negatively affected respect to the plain concrete. Application as a surface treatment decreased porosity and led to a higher amorphous SiO2 content. The material cohesion and impact resistance was increased by this application, although penetration was limited to the first 4 mm and the hydrophobic properties were more susceptible to mechanical damages to the surface. © 2021 The AuthorsThis project has received funding from the European Union's Horizon 2020 - Research and Innovation Framework Programme under grant agreement No 760858; This work has been financed by the Spanish State Research Agency R&D program 2020 (Project reference: PID2020-115843RB-I00); This work has been co-financed by the European Union under the 2014-2020 ERDF Operational Programme and by the Department of Economic Transformation, Industry, Knowledge, and Universities of the Regional Government of Andalusia (Project reference: FEDER- UCA18-106613)