Transformation of Amorphous Calcium Carbonate in Air - The Role of Additives and Humidity

2020 ◽  
Author(s):  
Katja Goetschl ◽  
Tina Spirk ◽  
Bettina Purgstaller ◽  
Martin Dietzel
Keyword(s):  
Calcium Carbonate ◽  
Pore Size ◽  
Large Body ◽  
Industrial Applications ◽  
Advanced Materials ◽  
Amorphous Calcium Carbonate ◽  
Mineralogical Characterization ◽  
Standard Material ◽  
Porosity Evolution ◽  
Material Porosity

<p>Amorphous calcium carbonate (ACC) is one of the six well-known CaCO<sub>3</sub><sup>.</sup>nH<sub>2</sub>O (0 ≤ n ≤ 6) solids and is of vast interest in the development of advanced materials. ACC offers enhanced performance compared to its crystalline equivalents due to its high solubility, specific surface and porosity. A large body of studies has been devoted to the applicability of ACC in pharmaceutical and industrial domains, pointing out material porosity to be a key property for its application. However, less is known about the material porosity evolution during ACC transformation into crystalline calcium carbonate (e.g. calcite or vaterite).</p><p>In this study we investigate the transformation of ACC in air and the effect of three additives (magnesium chloride, activated carbon and xanthan) at distinct humidities on the properties of the final crystalline product. ACC standard material was synthesized in either pure form or together with one of the above additives, stamped into a pellet, and exposed to 40 or 75 % RH. Mineralogical characterization of the crystalline products exhibits individual quantitative polymorph distribution induced by different additives and humidities. The most prominent result of the present study is the highly dissimilar pore size distribution when the ACC pellets were exposed to different humidities. Scanning electron microscopy combined with an image analysis software revealed 75 % RH to cause an increase of pore size of the final product by a factor of 10. These findings have significant implications to tailor and improve ACC nanomaterial designs and syntheses for pharmaceutical and industrial applications.</p>

scholarly journals Pure hydroxyapatite synthesis originating from amorphous calcium carbonate

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Michika Sawada ◽  
Kandi Sridhar ◽  
Yasuharu Kanda ◽  
Shinya Yamanaka
Keyword(s):  
Calcium Carbonate ◽  
Calcium Phosphate ◽  
Room Temperature ◽  
Molar Ratio ◽  
Final Phase ◽  
Amorphous Calcium Carbonate ◽  
Phosphate Compound ◽  
Synthesis Strategy ◽  
Phosphorylation Reaction ◽  
Subsequent Calcination

AbstractWe report a synthesis strategy for pure hydroxyapatite (HAp) using an amorphous calcium carbonate (ACC) colloid as the starting source. Room-temperature phosphorylation and subsequent calcination produce pure HAp via intermediate amorphous calcium phosphate (ACP). The pre-calcined sample undergoes a competitive transformation from ACC to ACP and crystalline calcium carbonate. The water content, ACC concentration, Ca/P molar ratio, and pH during the phosphorylation reaction play crucial roles in the final phase of the crystalline phosphate compound. Pure HAp is formed after ACP is transformed from ACC at a low concentration (1 wt%) of ACC colloid (1.71 < Ca/P < 1.88), whereas Ca/P = 1.51 leads to pure β-tricalcium phosphate. The ACP phases are precursors for calcium phosphate compounds and may determine the final crystalline phase.

scholarly journals Coal Fly Ash Derived Silica Nanomaterial for MMMs—Application in CO2/CH4 Separation

Membranes ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 78
Author(s):  
Marius Gheorghe Miricioiu ◽  
Violeta-Carolina Niculescu ◽  
Constantin Filote ◽  
Maria Simona Raboaca ◽  
Gheorghe Nechifor
Keyword(s):  
Fly Ash ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Coal Fly Ash ◽  
High Surface ◽  
Industrial Applications ◽  
Mixed Matrix Membranes ◽  
Co2 Removal ◽  
Mcm 41

In order to obtained high selective membrane for industrial applications (such as natural gas purification), mixed matrix membranes (MMMs) were developed based on polysulfone as matrix and MCM-41-type silica material (obtained from coal fly ash) as filler. As a consequence, various quantities of filler were used to determine the membranes efficiency on CO2/CH4 separation. The coal fly ash derived silica nanomaterial and the membranes were characterized in terms of thermal stability, homogeneity, and pore size distribution. There were observed similar properties of the obtained nanomaterial with a typical MCM-41 (obtained from commercial silicates), such as high surface area and pore size distribution. The permeability tests highlighted that the synthesized membranes can be applicable for CO2 removal from CH4, due to unnoticeable differences between real and ideal selectivity. Additionally, the membranes showed high resistance to CO2 plasticization, due to permeability decrease even at high feed pressure, up to 16 bar.

Numerical Approaches for Modeling Gas–Solid Fluidized Bed Reactors: Comparison of Models and Application to Different Technical Problems

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Peter Ostermeier ◽  
Annelies Vandersickel ◽  
Stephan Gleis ◽  
Hartmut Spliethoff
Keyword(s):  
Calcium Carbonate ◽  
Size Distribution ◽  
Fluidized Bed ◽  
Fluid Model ◽  
Industrial Applications ◽  
Small Scale ◽  
Fluidized Bed Reactors ◽  
Discrete Phase Model ◽  
Technical Problems ◽  
Numerical Approaches

Gas–solid fluidized bed reactors play an important role in many industrial applications. Nevertheless, there is a lack of knowledge of the processes occurring inside the bed, which impedes proper design and upscaling. In this work, numerical approaches in the Eulerian and the Lagrangian framework are compared and applied in order to investigate internal fluidized bed phenomena. The considered system uses steam/air/nitrogen as fluidization gas, entering the three-dimensional geometry through a Tuyere nozzle distributor, and calcium oxide/corundum/calcium carbonate as solid bed material. In the two-fluid model (TFM) and the multifluid model (MFM), both gas and powder are modeled as Eulerian phases. The size distribution of the particles is approximated by one or more granular phases with corresponding mean diameters and a sphericity factor accounting for their nonspherical shape. The solid–solid and fluid–solid interactions are considered by incorporating the kinetic theory of granular flow (KTGF) and a drag model, which is modified by the aforementioned sphericity factor. The dense discrete phase model (DDPM) can be interpreted as a hybrid model, where the interactions are also modeled using the KTGF; however, the particles are clustered to parcels and tracked in a Lagrangian way, resulting in a more accurate and computational affordable resolution of the size distribution. In the computational fluid dynamics–discrete element method (CFD–DEM) approach, particle collisions are calculated using the DEM. Thereby, more detailed interparticulate phenomena (e.g., cohesion) can be assessed. The three approaches (TFM, DDPM, CFD–DEM) are evaluated in terms of grid- and time-independency as well as computational demand. The TFM and CFD–DEM models show qualitative accordance and are therefore applied for further investigations. The MFM (as a variation of the TFM) is applied in order to simulate hydrodynamics and heat transfer to immersed objects in a small-scale experimental test rig because the MFM can handle the required small computational cells. Corundum is used as a nearly monodisperse powder, being more suitable for Eulerian models, and air is used as fluidization gas. Simulation results are compared to experimental data in order to validate the approach. The CFD–DEM model is applied in order to predict mixing behavior and cohesion effects of a polydisperse calcium carbonate powder in a larger scale energy storage reactor.

scholarly journals On the Relation of Amorphous Calcium Carbonate and the Macromechanical Properties of Sea Urchin Spines

2020 ◽  
Vol 22 (4) ◽  
pp. 1900922 ◽  
Author(s):  
Christoph Lauer ◽  
Sebastian Haußmann ◽  
Patrick Schmidt ◽  
Carolin Fischer ◽  
Doreen Rapp ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Sea Urchin ◽  
Amorphous Calcium Carbonate ◽  
Sea Urchin Spines

scholarly journals Transformation mechanism of amorphous calcium carbonate into calcite in the sea urchin larval spicule

2008 ◽  
Vol 105 (45) ◽  
pp. 17362-17366 ◽  
Author(s):  
Y. Politi ◽  
R. A. Metzler ◽  
M. Abrecht ◽  
B. Gilbert ◽  
F. H. Wilt ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Sea Urchin ◽  
Amorphous Calcium Carbonate ◽  
Transformation Mechanism

scholarly journals Amorphous calcium carbonate transforms into calcite during sea urchin larval spicule growth

1997 ◽  
Vol 264 (1380) ◽  
pp. 461-465 ◽  
Author(s):  
Elia Beniash ◽  
Joanna Aizenberg ◽  
Lia Addadi ◽  
Stephen Weiner
Keyword(s):  
Calcium Carbonate ◽  
Sea Urchin ◽  
Amorphous Calcium Carbonate

Biological control over the formation and storage of amorphous calcium carbonate by earthworms

2008 ◽  
Vol 72 (1) ◽  
pp. 227-231 ◽  
Author(s):  
M. J. I. Briones ◽  
E. López ◽  
J. Méndez ◽  
J. B. Rodríguez ◽  
L. Gago-Duport
Keyword(s):  
Electron Microscopy ◽  
Biological Control ◽  
Calcium Carbonate ◽  
Ostwald Ripening ◽  
High Resolution Electron Microscopy ◽  
Amorphous Calcium Carbonate ◽  
Concentrated Suspension ◽  
Selected Area Electron Diffraction ◽  
Resolution Electron ◽  
Glandular Secretion

AbstractThe earthworm calciferous gland produces a concentrated suspension of calcium carbonate and in certain species precipitates as concretions of CaCO3, which then enter the soil. Here we investigated the initial stages of CaCO3 formation in the earthworm Lumbricus friendi by means of Fourier transform infrared and electron microscopy techniques (field-emission scanning electron microscopy, transmission electron microscopy, high resolution electron microscopy and selected area electron diffraction). In addition, comparisons between the IR spectra of the water-dissolved carbonic anhydrase (CA) and the glandular secretion (‘milky fluid’) were performed in order to investigate the mechanisms involved in CaCO3 precipitation. Our results strongly suggest that carbonation starts with the dissolved CO2, which is transformed via deprotonation to HCO3-, then to CO32- and finally to amorphous calcium carbonate (ACC). While ACC stabilization takes place under the biological control, further transformation stages leading to calcite concretions seem to be inorganically driven by an Ostwald ripening process.

Bentonite Clays Characterization in the Town of Sossego – Paraiba State

2015 ◽  
Vol 820 ◽  
pp. 65-70
Author(s):  
I.D.S. Pereira ◽  
V.N.F. Lisboa ◽  
I.A. Silva ◽  
J.M.R. Figueirêdo ◽  
G.A. Neves ◽  
...  
Keyword(s):  
Industrial Applications ◽  
Particle Size Analysis ◽  
Size Analysis ◽  
Drilling Fluids ◽  
X Ray Diffraction ◽  
Mineralogical Characterization ◽  
Bentonite Clays ◽  
The Town ◽  
Petroleum Drilling

Bentonite exhibt a range of industrial applications moving millions of dollars on the market per year. Among several applications if highlights it is use for petroleum drilling fluids. Thus, this work aims to characterize physical, mineralogical and technologically, the bentonitics clays of Sossego County, Paraíba, Brazil. Mineralogical characterization of clays was done through the following techniques: particle size analysis by laser diffraction, thermogravimetric and differential thermal analysis, chemical analysis and x-ray diffraction. The clays were turned in by treatment with sodium in Na2CO3 and then determined whether the apparent viscosity, plastic and volume of filtrate of clay-water dispersions. The results showed that the samples are of polycationic, showing levels of MgO, CaO and K2O, similar to those from Boa Vista County, Paraíba, Brazil, and consist of clay mineral kaolinite, quartz and esmec. The clays showed rheological properties that indicate potential for use in drilling fluids.

Structural characterization of amorphous calcium carbonate-binding protein: an insight into the mechanism of amorphous calcium carbonate formation

2013 ◽  
Vol 453 (2) ◽  
pp. 179-186 ◽  
Author(s):  
Jingtan Su ◽  
Xiao Liang ◽  
Qiang Zhou ◽  
Guiyou Zhang ◽  
Hongzhong Wang ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Binding Sites ◽  
Binding Protein ◽  
Homology Modelling ◽  
Size Exclusion ◽  
Structural Basis ◽  
Amorphous Calcium Carbonate ◽  
Carbonate Formation

ACC (amorphous calcium carbonate) plays an important role in biomineralization process for its function as a precursor for calcium carbonate biominerals. However, it is unclear how biomacromolecules regulate the formation of ACC precursor in vivo. In the present study, we used biochemical experiments coupled with bioinformatics approaches to explore the mechanisms of ACC formation controlled by ACCBP (ACC-binding protein). Size-exclusion chromatography, chemical cross-linking experiments and negative staining electron microscopy reveal that ACCBP is a decamer composed of two adjacent pentamers. Sequence analyses and fluorescence quenching results indicate that ACCBP contains two Ca2+-binding sites. The results of in vitro crystallization experiments suggest that one Ca2+-binding site is critical for ACC formation and the other site affects the ACC induction efficiency. Homology modelling demonstrates that the Ca2+-binding sites of pentameric ACCBP are arranged in a 5-fold symmetry, which is the structural basis for ACC formation. To the best of our knowledge, this is the first report on the structural basis for protein-induced ACC formation and it will significantly improve our understanding of the amorphous precursor pathway.

Sign in / Sign up

Export Citation Format

Share Document