CO2 conversion through the synthesis of CaCO3 nanoparticles

L'abstract è presente nell'allegato / the abstract is in the attachmen

Nucleation and growth kinetics of CaCO3 crystals in the presence of foreign monovalent ions

The aim of this work is to study the effect of the presence of different monovalent ions (Na+, NH4+ and K+) on the nucleation and growth rates of CaCO3 precipitation. There is currently great interest in the precipitation of CaCO3 particles reusing CO2 rich flue gases and calcium-rich wastes, which implies the presence of foreign ions that can affect the crystallization process. Unseeded and seeded tests were carried out in a batch system to estimate the nucleation and growth kinetics, respectively. Tests with Na2CO3 and CaCl2 as precursors led to the classical calcite crystallization mechanism via vaterite formation at high supersaturations. On the other hand, the use of (NH4)2CO3 entailed lower pH and the presence of NH4+, which stabilized the vaterite and avoided its transformation into stable calcite crystals. Thus, faster nucleation kinetics by using Na2CO3 were obtained. To estimate the growth rate, tests with two initial seed loadings and types (micro and nano seed) were performed. The growth rate increased with the crystal size and decreased with the magma density. The results indicate that the ion effect on the growth rate seems to be related to the ionic radius of the foreign ion

Optimization of CaCO3 synthesis through the carbonation route in a packed bed reactor

This article presents an investigation on the recovery of CO2 from the combustion gases of the cement industry through a carbonation route in order to obtain Calcium Carbonate Nanoparticles (CCnP), which could find application as either polymer or cement fillers. Two different experimental setups, a Continuously Stirred Bubbling Reactor (CSBR) and a Packed Bed Reactor (PBR), were studied in order to improve the final product and enhance the process yield. The influence of the experimental parameters on the particle size and morphology was tested for both reactors. The process was intensified by employing the PBR, where cubic calcite particles smaller than 300 nm were synthesized and higher CO2 conversions were obtained with respect to the CSBR performance

Sequential curing of thiol-acetoacetate-acrylate thermosets by latent Michael addition reactions

Thiol-acetoacetate-acrylate ternary dual-curing thermosets were prepared by a sequential process consisting of thiol-Michael addition to acrylates at room temperature followed by Michael addition of acetoacetates to acrylates at moderately elevated temperature. The curing sequence can be controlled with the help of the different acidities of the protons on thiol and acetoacetate groups, the favorable pKa of the base used as catalyst and the self-limiting character of Michael additions. The latency of the curing steps can be regulated by selection of the right catalysts, temperature and curing conditions. The properties of the intermediate and final materials can be tuned by changing the structure of the monomers and the contribution of both Michael addition reactions.Postprint (author's final draft

Toxicological profile of calcium carbonate nanoparticles for industrial applications.

Calcium carbonate nanoparticles (CaCO3NPs) derived from CO2 are promising materials for different industrial applications. It is imperative to understand their toxicological profile in biological systems as the human and environmental exposures to CaCO3NPs increases with growing production. Here, we analyse the cytotoxicity of CaCO3NPs synthesized from a CaO slurry on two cell lines, and in vivo on zebrafish (Danio Rerio). Our results demonstrate the CaCO3NPs in vitro safety as they do not cause cell death or genotoxicity. Moreover, zebrafish treated with CaCO3NPs develop without any abnormalities, confirming the safety and biocompatibility of this nanomaterial

Evaluation of the mechanical properties of cements with fillers derived from the CO2 reduction of cement plants

This work introduces a novel method for the development of CO2 recovery systems derived from the production process of cement in order to obtain CaCO3 nanofiller in cement-based composites. Research was carried out in collaboration between the Department of Applied Science and Technology (DISAT) and the Department of Structural, Construction and Geotechnical Engineering (DISEG) of Politecnico di Torino. The objective of this method was dual. Firstly, it aimed to obtain a precipitated calcium carbonate - nanoCaCO3 - with a high degree of purity. Secondly, it aimed to optimize the characteristics of these nanoparticles e.g. additional percentages, morphology, particle size distribution or crystal phase, according to their use in cement-based composites. The synthesized nanoCaCO3 particles were subsequently added into the cementitious composites in different percentages according to the weight of the cement, in order to understand their behaviour within the cement matrix. The mechanical properties were also evaluated, both at 7 and 28 days, through three point bending and compression tests. The results of the mechanical tests showed a promising improvement in strength and toughness. This study is a first step towards developing a CO2 circular economy

Nano CaCO3 particles in cement mortars towards developing a circular economy in the cement industry

Abstract This paper calls into question the effects of incorporating nano calcium carbonate (CaCO3) particles in cement mortars, as they are interesting additive materials already successfully tested as cement nanofiller. These nanoparticles could potentially be prepared through the carbonation route using CO2 from combustion gases from the cement industry. This could enable a circular-economy approach for carbon capture and its re-use within the cement industry, in a sustainable and synergistic manner. In this study, part of the cement content was substituted with commercial nano CaCO3 particles to investigate their effects on the flexural and compressive strength of the resulting cement mortars, after curing for 7 and 28 days. Decreasing the cement content could lead to a reduction in the carbon footprint of cement, which is responsible for approximately 8% of global carbon dioxide emissions. Preliminary results using synthesized CaCO3 particles as nanofillers showed that, after 7 days of curing, mechanical properties of cement mortars improved. This indicates that hydration reaction was accelerated since CaCO3 acts as seeding for this reaction. By contrast, after 28 days of curing, no major improvement was observed. A higher content of calcium carbonate nanoparticles may have reduced the filler effect of these particles due to aggregation phenomena. In the present work, the effects of commercial nano CaCO3 particles on cement hydration were investigated. Mechanical tests showed promising results both after 7 and 28 days of curing. This could lead to the reduction of the carbon footprint of cement manufacturing and produce increasingly better performing building materials. Thus, the development of a circular economy in the cement industry could be achieved

Relaciones interpersonales y la percepción de la calidad educativa de los estudiantes del décimo ciclo de la Facultad de Derecho de una universidad de Ica, durante el periodo 2021-II

La presente investigación tiene como objetivo explicar cómo contribuye las relaciones interpersonales a la percepción de la calidad educativa de los estudiantes del décimo ciclo de la Facultad de Derecho de una Universidad de Ica, durante el periodo 2021-II. La metodología se realizó bajo el enfoque cualitativo de la investigación, siendo el alcance de la investigación explicativo. Se centra en explicar porque ocurre el fenómeno del efecto que tiene las relaciones interpersonales entre los sujetos del proceso educativo con la percepción de la calidad educativa. Por lo cual el diseño de la investigación es del tipo fenomenológico. Los resultados han sido producto de las entrevistas realizadas a los estudiantes que conformaron la muestra, siendo el tipo de muestreo no probabilístico por conveniencia, por lo que se seleccionó a 15 estudiantes a quienes se les aplicó la guía de entrevista con 21 preguntas sobre relaciones interpersonales y sus categorías: inclusión en grupos de trabajo, control ejercido por el docente, vínculo afectivo y las categorías de calidad educativa: Soporte en tutoría, pertinencia educacional y didáctica del docente. La cuales se grabaron con autorización de los entrevistados vía zoom. Los resultados muestran que las relaciones interpersonales son importantes para fortalecer la calidad educativa de los estudiantes y así conseguir la mejora continua. Los resultados han mostrado una contribución del trabajo en equipo y la inclusión, el control del docente y generación de un vínculo afectivo, que han permitido a su vez el adecuado soporte de tutoría no solo para el seguimiento sino para el apoyo profesional y seguimiento con el docente de los planes de estudio. Siendo importante que el docente cada día mejore su performance en la didáctica en clase.Escuela de Postgrad

Nearly zero CO2 cementitious composites

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