Adsorption of phenol from aqueous solution by activated carbons derived from cherry stones

En este trabajo se han preparado carbones activados mediante activación física (con aire, dióxido de carbono y vapor de agua) a partir de huesos de cereza. Los carbones activados se han caracterizado desde el punto de vista textural (adsorción de nitrógeno a 77 K y porosimetría de mercurio) y químico (grupos superficiales de oxígeno y punto de carga cero). Las muestras preparadas se han empleado para adsorber fenol en disolución, mostrando mayor capacidad de adsorción a medida que lo hace la superficie específica y microporosidad. No obstante, la adsorción química de fenol se vio favorecida por la presencia de grupos superficiales de oxígeno en el carbón. Los carbones preparados con dióxido de carbono y vapor de agua mostraron una capacidad de adsorción de fenol comparable a la del carbón comercial Filtrasorb-400.Samples of activated carbon were obtained by physical activation (air, carbon dioxide and steam as activating agents) of cherry stones. Activated carbon samples were characterized from the textural (nitrogen adsorption at 77 K and mercury porosimetry) and surface chemistry (surface oxygen groups and point of zero charge) points of view. Samples were used to adsorb phenol from aqueous solution, showing that phenol uptake was related to the surface area and microporosity. Nevertheless, chemisorption of phenol was favoured by surface oxygen groups. Samples activated in CO2 and steam showed phenol adsorption capacities close to that of Filtrasorb-400, a well-known commercial activated carbon.Trabajo patrocinado por: Junta de Extremadura. Proyecto PDT08-A012peerReviewe

Historical thinking, causal explanation and narrative discourse in trainee teachers in Spain

This paper examines the historical thinking skills of 283 students studying a Primary Education degree in Spain. In order to achieve this objective, we analysed texts they had written on a substantive historical event: the Christian expansion into the Muslim-ruled territories of the Iberian Peninsula. We employed a qualitative methodology in order to determine the level of presentational complexity according to the knowledge demonstrated, the second-order concepts included in their texts and the way in which the causal application of the process was expressed. This was combined with a quantitative assessment of the levels of complexity and their relationship with the cognitive levels of the texts according to the SOLO taxonomy. The results, demonstrated in the task, confirm that trainee teachers have extremely limited skills relating to history and a simplistic model of causal explanation, based on the contrast between union/hegemony and disintegration/weakness. This discourse is inherited from the national narrative imposed since the times of 19th century historiographyThis paper is the result of research project EDU2015-65621-C3-R “Competencias sociales para una ciudadanía democrática: análisis, desarrollo y evaluación”; EDU2015-65621-C3-2-R “La evaluación de las competencias y el desarrollo de capacidades cognitivas sobre historia en Educación Secundaria Obligatoria”; EDU2014-51720- REDT RED 14 “Red de investigación en enseñanza de las ciencias sociales"S

Narrating “Histories of Spain”. Student teachers and the construction of national narratives

This study analyses the role of Spanish teacher training students as narrators of what they consider to be the history of Spain. Results of this empirical study are based on a random sample of 103 narratives produced by trainee primary education teachers (20-22 years of age) studying at the University of Murcia. We are interested in understanding the role of students as agents of historical knowledge. Recent research in history education has stressed the need to vindicate the active role of students in the creation of historical narratives. How do students construct their accounts of history? How do they reflect narratives of school-taught history? Their narratives always reveal certain forms and skills employed to represent the past. This study focuses on this perspective. We have analysed their extra-curricular knowledge (family, social environments, mass media and other cultural products such as TV series, videogames, websites, etc.) and their memories of school history (curriculum, textbooks, teachers) using a mixed quantitative and qualitative methodology. Our qualitative methodology is based on grounded theory and, in order to analyse discourse, we have used quantitative methodology with the analysis of key events and historical figures present in the narrative, in an attempt to categorise second order concepts and sources of historical knowledge. In the results, essentialist and traditional representations of this historical knowledge can be appreciated. Reported major events are related to a traditional political reading of history and linked to genesis and nation-building events: showing heroes and antiheroes of a national narrative. Regarding the sources of knowledge, teachers’ explanations, textbooks and museums are the factors most valued by studentsEste artigo é o resultado do proxecto EDU2015-65621-C3-R “Competencias sociales para una ciudadanía democrática: análisis, desarrollo y evaluación”; EDU2015-65621-C3-2-R “La evaluación de las competencias y el desarrollo de capacidades cognitivas sobre historia en Educación Secundaria Obligatoria”; EDU2014-51720- REDT RED 14 “Red de investigación en enseñanza de las ciencias sociales”S

Preparation of activated carbon-metal (hydr) oxide materials by thermal methods. Thermogravimetric-mass spectrometric (TG-MS) analysis

[EN] tActivated carbon (AC)-metal (hydr) oxide (MO) materials prepared by wet impregnation of a commercialAC with Al3+, Fe3+, Zn2+, SnCl2, TiO2and WO42−in water at pH between 1.37 and 9.54 in two successivesoaking and oven-drying steps are analysed by thermogravimetry-mass spectrometry (TG-MS) between25 and 900◦C. Under identical conditions, a blank sample (ACB) was first prepared using deionized waterand then thermally analyzed. The mass loss in the TG analysis is 1.35 wt% for AC, 2.12 wt% for ACB, andbetween 2.47 and 23.20 wt% for the AC-MO materials. For these materials, it depends on the impregnationagent and varies by SnCl2> Fe3+> Al3+> Zn2+> WO42−> TiO2. The number of thermal effects giving off CO2and CO is larger with the Al3+, Fe3+and Zn2+ions than with SnCl2, TiO2and WO42−. It is so in particular forCO2with the Fe3+ion and for CO with the Al3+ion. In general, the release of CO at high temperature hasbeen associated with the carbothermal reduction of metal oxides. As a result of the reaction low-meltingpoint metals such as Al, Zn and Sn, unlike Fe and W, are formed which vaporize and thereby contribute tothe mass loss. Only with Fe3+and TiO2, the amount of desorbed water is larger by dehydroxylation thanby dehydration. The masses of evolved H2O, CO2and CO are by far higher with SnCl2, whereas they arelower with TiO2and WO42−

Preparation and Microstructural Characterization of Activated Carbon-Metal Oxide Hybrid Catalysts: New Insights into Reaction Paths

[EN] In catalysis processes, activated carbon (AC) and metal oxides (MOs) are widely used either as catalysts or as catalyst supports because of their unique properties. A combination of AC and MO nanoparticles in a single hybrid material usually entails both chemical and microstructural changes, which may largely influence the potential catalytic suitability and performance of the resulting product. Here, the preparation of a wide series of AC MO hybrid catalysts is studied. Three series of such catalysts are prepared by support first of MO (Al2O3, Fe2O3, SnO2, TiO2, WO3, and ZnO) precursors on a granular AC by wet impregnation and oven-drying at 120 ºC, and by subsequent heat treatment at 200 or 850 ºC in inert atmosphere. Both the chemical composition and microstructure are mainly investigated by powder X-ray diffraction. Yield and ash content are often strongly dependent on the MO precursor and heat treatment temperature, in particular for the Sn catalysts. With the temperature rise, trends are towards the transformation of metal hydroxides into metal oxides, crystallinity improvement, and occurrence of drastic composition changes, ultimately leading to the formation of metals in elemental state and even metal carbides. Reaction paths during the preparation are explored for various hybrid catalysts and new insights into them are provided

Physico-chemical characterization of activated carbon–metal oxide photocatalysts by immersion calorimetry in benzene and water

[EN] From a commercial activated carbon (AC) and Al3?, Fe3?, Zn2?, SnCl2, TiO2 and WO4 2- in water, three series of AC–metal (hydr)oxide (MO) samples prepared by wet impregnation in two successive steps of soaking at 80 ºC and oven-drying at 120 ºC (S1) and subsequent heat treatment at 200 (S2) or 850 C (S3) were characterized texturally by N2 adsorption at -196 C and by immersion calorimetry in benzene and water. The mass changes associated with the preparation of the samples are usually stronger for S1 and S3 than for S2. The incorporation of MO to AC causes a greater decrease in the micropore volume and pore narrowing only for the SnCl2-impregnated sample. The opposite effects on the microporous structure are noted for most S2 and S3, as compared to S1. For AC, -DiH(C6H6) is 114.0 J g-1 and -DiH(H2O) is 30.5 J g-1. For the AC–MO samples, -DiH(C6H6) and Stot(C6H6) are generally lower than for AC and vary by S3[S2[S1. However, -DiH(H2O), Stot(H2O) and [O] are usually lower for S3. Stot(C6H6) is higher for the samples prepared using the metal ions. The results of immersion calorimetry for AC and AC–MO samples provide one with valuable information concerning the dependence of the hydrophobicity and hydrophilicity of the samples on the method used in their preparation

Analysis of Passenger Car Turbocharged Diesel Engines Performance When Tested at Altitude and of the Altitude Simulator Device Used

[EN] According to current worldwide trends for homologation vehicles in real driving conditions is forced to test the engines in altitude and in highly dynamic driving cycles in order to approach nowadays and next future emissions standard. Up to now, there were two main options to perform this type of tests: round-robin tests of the whole vehicle or hypobaric chambers, both with high costs and low repeatability. In this paper a new device is described, which can emulate ambient conditions at whatever altitude between sea level and 5000m high. Even it can be used to emulate ambient conditions at sea level when test bench is placed up to 2000m high. The main advantages of the altitude simulation equipment are as follows: dynamic emulation of all the psychrometric variables affecting the vehicles during round-robin tests; lower space usage and low-energy consumption. The altitude simulator (AS) has been validated comparing with results from a hypobaric chamber at different altitudes. Previously a research about the dispersion in the measurements of both testing devices has been done for assessing the results of the comparison experiment. Final conclusion resulted in the same operating performance and emissions of the studied engine with both types of testing equipment for altitude simulation.FEDER, Government of Spain through Project TRA2016-79185-R (Funder ID: 10.13039/501100002924).Broatch, A.; Bermúdez, V.; Serrano, J.; Tabet, R.; Gómez, J.; Bender, S. (2019). Analysis of Passenger Car Turbocharged Diesel Engines Performance When Tested at Altitude and of the Altitude Simulator Device Used. Journal of Engineering for Gas Turbines and Power. 141(8):1-9. https://doi.org/10.1115/1.4043395S191418Hiroyasu, H., Arai, M., & Tabata, M. (1989). Empirical Equations for the Sauter Mean Diameter of a Diesel Spray. SAE Technical Paper Series. doi:10.4271/890464Gómez, J., 2018, “Development of an Altitude Simulator and Analysis of the Performance and Emissions of Turbocharged Diesel Engines at Different Altitudes,” Ph.D. thesis, Universitat Politècnica de València, Valencia, Spain.https://riunet.upv.es/bitstream/handle/10251/101284/G%C3%93MEZ%20-%20Development%20of%20an%20altitude%20simulator%20and%20analysis%20of%20the%20performance%20and%20emissions%20of%20tur....pdf?sequence=1Toff, W. D., Jones, C. I., Ford, I., Pearse, R. J., Watson, H. G., Watt, S. J., … Greaves, M. (2006). Effect of Hypobaric Hypoxia, Simulating Conditions During Long-Haul Air Travel, on Coagulation, Fibrinolysis, Platelet Function, and Endothelial Activation. JAMA, 295(19), 2251. doi:10.1001/jama.295.19.2251Bermúdez, V., Serrano, J. R., Piqueras, P., Gómez, J., & Bender, S. (2017). Analysis of the role of altitude on diesel engine performance and emissions using an atmosphere simulator. International Journal of Engine Research, 18(1-2), 105-117. doi:10.1177/146808741667956

Surface morphological characterization of activated carbon-metal (hydr)oxide composites: some insights into the role of the precursor chemistry in aqueous solution

[EN] Morphological features of metal (hydr)oxide (MO) particles supported on activated carbon (AC) largely influence the performance of these composite materials in most of their applications, particularly in heterogeneous catalysis. Furthermore, the MO precursor as well as the preparation method and conditions strongly determine these morphological features. Thus, the present work is aimed at shedding light on the role of the precursor chemistry on the surface morphology of a series of AC-MO composites prepared by wet impregnation of a commercial AC with Al(NO3)3, Fe(NO3)3, and Zn(NO3)2 in aqueous solution. These materials are characterized by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. The microstructure, morphology, size distribution and degree of dispersion of the supported MO (nano)particles strongly depend on the chemical transformations undergone by the precursors not only in the impregnation solutions after their contact with AC but also during the oven-drying step. Al3þ, Fe3þ and Zn2þ species in aqueous medium are involved in hydrolysis and polymerization processes, which notably modify the pH of the starting precursor solutions. Upon their contact with AC, pH markedly increases due to the strong basic character of the carbon surface (pHpzc 10.50), leading to the precipitation of the metal hydroxides or oxyhydroxides. Both supported bayerite (a-Al(OH)3) and goethite (a-FeO(OH)) are essentially amorphous; however, the former grows in micrometric particles while the latter does as nanoparticles. By contrast, the higher crystallinity and larger particle size of supported w€ulfingite (e-Zn(OH)2) are connected with an additional transformation of the as-precipitated amorphous hydroxide during the heating step at 120 C

FT-IR Analysis of Pyrone and Chromene Structures in Activated Carbon

[EN] The behavior of activated carbon in many catalysis processes is determined by the basic character of its surface. Using FT-IR spectroscopy, an attempt is made here to identify not only pyrone and chromene type structures but also their isomers in a commercial activated carbon (Merck; AC). The infrared analysis between 400 and 4000 cm−1 focuses on the keto (−CO) group in pyrones, methylene (−CH2−) group in chromenes, and enol ether group (O−CC) in both kinds of structures. Although overlapping bands are frequent in the AC spectrum, occurrence of most significant pyrone and chromene absorptions proves their presence in AC. This is so in particular for 2-pyrone and 4H-chromene, whereas 4-pyrone is less amenable to the infrared analysis

Preparation of activated carbon-metal oxide hybrid catalysts: textural characterization

[EN] In catalysis processes, activated carbon (AC) and metal oxides (MOs) are used as catalysts and catalyst supports because of their textural and chemical properties. A combination of AC andMO properties in a single catalyst entails changes in the catalytic activity and behaviour which would redound to the number of applications. The present study aims at preparing AC-MO hybrid catalysts by chemical interaction of MO precursors in aqueous medium with AC and at carrying out the textural characterization of the samples. From a commercial AC and six MO precursors (i.e. Fe3+, Al3+, Zn2+, SnCl2, TiO2, andWO4 2 −), three series of hybrid catalysts were prepared by wet impregnation and oven-drying at 120 °C and subsequent heat treatment of the resulting products at 200 or 850 °C in inert atmosphere. The samples were characterized texturally by N2 adsorption at−196 °C, mercury porosimetry, and density measurements. Therefore, the influence of theMO precursor and heating conditions on the porous texture is studied. Yield varies more widely for the samples prepared at 120 °C and 850 °C than at 200 °C. The mass increase after oven-drying at 120 °C and the mass decrease after heating at 850 °C are much greater for the Sn catalysts. Because of the support ofMO precursors on AC, in general, macro-, meso-, and microporosity significantly decrease. The effects on the texture of AC are by far more important for the Sn catalyst and also, though less, for the Fe catalyst. However, they are weaker for theW and Ti catalysts. In general, the heat treatment at 200 °C only causes small changes in the porous texture of the samples. By heating at 850 °C the pore size distribution becomes more uniform in the three porosity regions. Microporosity develops chiefly for the Sn catalyst, whereas mesoporosity does mainly for the Sn and Fe catalysts. The textural modifications have been associated with mass, composition, and structural modifications