Characterization of mixed mortars with lime obtained from recycled phosphogypsum

La producción industrial del ácido fosfórico presenta una gran demanda debido al uso cada vez mayor de fertilizantes, detergentes o productos de limpieza. Este proceso genera cada año millones de toneladas de fosfoyesos como residuo. La posibilidad de incorporación de este residuo en el desarrollo de morteros tiene como objetivo principal generar un impacto medioambiental positivo a partir del reaprovechamiento del material de desecho como materia prima para la obtención de pasta de cal. Adicionalmente, el proceso desarrollado para la obtención de la pasta de cal implica la captura de CO2 ambiental por carbonatación del residuo tratado. Los morteros mixtos o bastardos de cemento y arena presentan mucha resistencia y endurecen rápidamente. La incorporación de cal aporta trabajabilidad y plasticidad, así como una mejor capacidad de adherirse a otros materiales. En este estudio se han preparado y caracterizado morteros mixtos con pasta de cal procedente del tratamiento de fosfoyesos en una dosificación 1:1:6 (cemento:cal:arena). Las características de estos morteros se han comparado con un mortero de referencia.The industrial production of phosphoric acid has a high demand due to the greater use of fertilizers, detergents or cleaning products. Every year, this process generates millions of tonnes of phosphogypsum waste. The possibility of incorporation of this waste in the mortar production is aimed to contribute to the environment from the reuse of the waste as raw material for the production of lime paste. In addition, the process developed to obtain the lime paste helps to reduce CO2 concentrations by carbonation of mortar. The sand and cement mixed or bastard mortars present much resistance and dries and hardens quickly. In addition, the lime brings workability and plasticity. An important property of the mortars is the ability to stick to material that are in contact. In the present study it has been prepared and characterize mixed mortars with lime paste from phosphogypsum treatment in a dosage 1:1:6 (cement:lime:sand). Mortars characteristics were compared with a reference mortar.Ministerio de Ciencia, Innovación y Universidades de España, MAT2017- 842228

Flue gas adsorption by single-wall carbon nanotubes: A Monte Carlo study

Adsorption of flue gases by single-wall carbon nanotubes (SWCNT) has been studied by means of Monte Carlo simulations. The flue gas is modeled as a ternary mixture of N2, CO2, and O2, emulating realistic compositions of the emissions from power plants. The adsorbed flue gas is in equilibrium with a bulk gas characterized by temperature T , pressure p, and mixture composition. We have consid- ered different SWCNTs with different chiralities and diameters in a range between 7 and 20 Å. Our results show that the CO2 adsorption properties depend mainly on the bulk flue gas thermodynamic conditions and the SWCNT diameter. Narrow SWCNTs with diameter around 7 Å show high CO2 adsorption capacity and selectivity, but they decrease abruptly as the SWCNT diameter is increased. For wide SWCNT, CO2 adsorption capacity and selectivity, much smaller in value than for the narrow case, decrease mildly with the SWCNT diameter. In the intermediate range of SWCNT diameters, the CO2 adsorption properties may show a peculiar behavior, which depend strongly on the bulk flue gas conditions. Thus, for high bulk CO2 concentrations and low temperatures, the CO2 adsorption capacity remains high in a wide range of SWCNT diameters, although the corresponding selectivity is moderate. We correlate these findings with the microscopic structure of the adsorbed gas inside the SWCNTs.Ministerio de Economía y Competitividad MAT2013-42934-R y FIS2012-3245

Hydration and carbonation reactions of calcium oxide by weathering: Kinetics and changes in the nanostructure

The weathering reactions of hydration and carbonation of nanostructured calcium oxide with atmospheric moisture and carbon dioxide have been characterized. This work is the first-to-date combined kinetic and nanostructural research on CaO oriented to two key processes for different systems, i.e. hardening of construction materials and carbon mineral sequestration. The evolution of the precipitated crystalline phases was monitored by X-ray diffraction and thermogravimetry, along with structural characterization by nitrogen physisorption, electron microscopy and small-angle scattering. Complete hydration of the samples was always found prior to the onset of carbon sequestration, which depended on the nanostructure of the samples. Hence, carbonation started after 300 h of weathering for samples with a specific surface area of 40 m2/g, whereas carbonation of the samples with 20 m2/g occurred after 550 h. Full carbonation from atmospheric CO2 (100% efficiency) was obtained in all cases. This combined research was completed by developing an empirical description of the weathering reactions in terms of a two-process Random Pore Model. Finally, this work aimed to determine the role of the nanostructure of samples based on industrial wastes as one of the most important factors for developing efficient carbon sequestration technologies.España Mineco MAT2013-42934-

Environmental Impact of Phosphogypsum-Derived Building Materials

The aim of the present work was to characterize the products obtained from the treatment of phosphogypsum residue by means of two recovery routes, and also to evaluate the concentrations of heavy metals and radionuclides in the materials obtained and their leachates. In this way, it is possible to determine how the most hazardous components of phosphogypsum behave during procedures until their stabilization through CO2 fixation. This study provides an initial estimate of the possibilities of reusing the resulting products from a health and safety risk standpoint and their potential polluting capacity. The phases resulting from the transformations were controlled, and the behaviour of standard mortars manufactured from the resulting paste lime was studied. In all cases, an additional control of the leachate products was performe

New method for carbon dioxide mineralization based on phosphogypsum and aluminium-rich industrial wastes resulting in valuable carbonated by-products

A new carbon mineralization method was designed based on a sequestration agent synthesised exclusively from industrial wastes. Phosphogypsum waste from the fertiliser industry was dissolved into caustic aqueous waste from the aluminium anodising industry. The resulting precipitate consisted of katoite (Ca3Al2(OH)12, a Si-free hydrogrossular solid solution end-member of the Al-containing hydrogarnet) and thenardite (Na2SO4); the latter easily removed by rinsing with water. The carbonation performance of this katoite-rich sequestration agent was evaluated using two different methods, by bubbling in aqueous media and by weathering. Both procedures yielded high carbonation efficiencies (80% and 100%, respectively), and resulted in a solid precipitate composed primarily of calcite (CaCO3) and aluminium hydroxide (Al(OH)3). Priority attention was given to the transfer of trace elements and radionuclides of the uranium series typically present in the phosphogypsum. Results confirmed that the traces were transferred to resulting final solid carbonate at concentrations similar to those present in the raw phosphogypsum. In conclusion, these carbonated minerals would trap substantial amounts of CO2 and produce final materials with similar civil engineering uses to those proposed for current phosphogypsum wastes. This work offers new methods for jointly managing specific industrial wastes oriented to more sustainable industrial processes and controlling CO2 emissionsGobierno de España MAT2013-42934- RJunta de Andalucía P12-RNM-226

Phosphogypsum waste lime as a promising substitute of commercial limes: A rheological approach

This paper presents the rheological properties of three types of lime putty, specifying the influence of their origin. The study aims to compare a special lime putty prepared from phosphogypsum with a commercial lime powder and an aged lime putty. The results obtained in terms of chemical composition, crystalline structure, grain size and rheological characterization, (linear viscoelasticity, shear rate and time-dependent flow behaviour) are presented in the study. Putties studied present a similar rheological response, which mainly depends on the particle size and water content. Lower values of the linear viscoelastic functions and viscosity were found for the phosphogypsum lime putty, in agreement with the higher particle size. Transient flow tests reveal a predominant elastic response with no significant shear-induced structural perturbations. However, either a thickening phenomenon over time, i.e. rheopexy, favoured at low shear rates, or a viscosity decrease, i.e. thixotropy, favoured at high shear rates, was observed

Propiedades de la cal en pasta obtenida a partir del tratamiento de fosfoyesos de la industria de fertilizantes

El proceso industrial de fabricación de ácido fosfórico tiene como materia prima principal la roca fosf orita, compue sta mayoritariamente por apatito (Ca 5 (PO 4 ) 3 OH); produciéndose el ácido fosfórico por un lado y por otro un subproducto formado principalmente por sulfato hidratado de calcio, denominado fosfoyeso. La producción de ácido fosfórico en Huelva (SO España) ha sido objeto de controversia por la formación de balsas de este subproducto, sin suficiente control, en las marismas de la desembocadura del río Tinto. Un grupo de investigadores liderados desde el Dpto. de Física de la Materia Condensada de la Universidad de Sevilla ha desarrollado un procedimiento sencillo y muy eficiente de obtención de portlandita, en forma de pasta de cal, como producto de la reacción química de u na disolución de fosfoyesos con una solución de sosa alcalina: CaSO 4 ·2H 2 O + 2NaOH Ca(OH) 2 + Na 2 SO 4 + 2H 2 O Como es previsible, la portlandita obtenida es susceptible de carbonatación, actuando como sumidero para el secuestro mineral de CO 2 . Esta metodolog ía tiene el potencial de reducir simultáneamente dos problemas ambientales: la gestión de los residuos industriales peligrosos; y las emisiones de gases de efecto invernadero. Este trabajo presenta la caracterización química, mineralógica, morfología y granulométrica del producto obtenido de cara su potencial utilización en aplicaciones relacionadas con el sector de la construcción, considerando inicialmente sus posibilidades como conglomerante y consolidant

Post-mortem findings in Spanish patients with COVID-19; a special focus on superinfections

IntroductionWhole-body autopsies may be crucial to understand coronavirus disease 2019 (COVID-19) pathophysiology. We aimed to analyze pathological findings in a large series of full-body autopsies, with a special focus on superinfections. MethodsThis was a prospective multicenter study that included 70 COVID-19 autopsies performed between April 2020 and February 2021. Epidemiological, clinical and pathological information was collected using a standardized case report form. ResultsMedian (IQR) age was 70 (range 63.75-74.25) years and 76% of cases were males. Most patients (90%,) had at least one comorbidity prior to COVID-19 diagnosis, with vascular risk factors being the most frequent. Infectious complications were developed by 65.71% of the patients during their follow-up. Mechanical ventilation was required in most patients (75.71%) and was mainly invasive. In multivariate analyses, length of hospital stay and invasive mechanical ventilation were significantly associated with infections (p = 0.036 and p = 0.013, respectively). Necropsy findings revealed diffuse alveolar damage in the lungs, left ventricular hypertrophy in the heart, liver steatosis and pre-infection arteriosclerosis in the heart and kidneys. ConclusionOur study confirms the main necropsy histopathological findings attributed to COVID-19 in a large patient series, while underlining the importance of both comorbid conditions and superinfections in the pathology

Recomendaciones para la práctica de ejercicio físico en pacientes cardiópatas en edad escolar

As cardiopatías conxénitas constitúen o defecto conxénito máis frecuente, e nas últimas décadas asistimos a un importante avance no tratamento das mesmas. Este documento consiste nunha recompilación de recomendacións para a práctica da actividade física, no ámbito escolar galego, para os nenos/as entre 6 e 16 anos, portadores da maioría das cardiopatías conxénitas e familiares.Las cardiopatías congénitas constituyen el defecto congénito más frecuente, y en las últimas décadas asistimos a un importante avance en el tratamiento de las mismas. Este documento consiste en una recopilación de recomendacións para la práctica de la actividade física, en el ámbito escolar gallego, para los niños y niñas entre 6 y 16 años, portadores de la mayoría de las cardiopatías congénitas y familiares