Cooperative effects of polarization and polyaspartic acid on …
— We demonstrated the crystallization of calcium carbonate (CaCO 3) on polarized calcite single crystal substrates with three different orientations characterized by the (10.0), (00.1), and (10.4) planes in the presence of polyaspartic acid (PAsp) as an organic additive.The precipitates had a multiple phase structure with thin-film-like and …
Biomimetic synthesis of calcite films by a polymer-induced …
— At constant calcium chloride and polymer (polyaspartic acid, sodium salt) concentrations, a pronounced influence of the Mg 2+ /Ca 2+ ratio was observed. Our experiments revealed an increasing inhibitory effect of Mg 2+ on calcite growth with the increase of Mg 2+ /Ca 2+ ratio in the parent solution, but this effect was manifest in …
Magnesium Ions Direct the Solid‐State Transformation of …
— Amorphous calcium carbonate (ACC) is a common precursor to crystalline calcium carbonate, and is of particular importance in biomineralization, where its crystallization in privileged environments ensures a pseudomorphic transformation. While organisms regulate this process using organic molecules and magnesium ions to …
A molecular insight into the mechanism of organic molecule …
— This work aimed to study the detachment mechanism of organic molecules by scCO 2 from a water invasion calcite surface. The model consisted of four layers: the calcite layer, the organic molecule layer, the water layer and the scCO 2 layer, as shown in Fig. 1.The calcite layer was built by cleaving the calcite (104) surface with a size of 40.97 Å × …
Thin-film-induced morphological instabilities over calcite …
— In particular, when calcium is leaving (entering) the water film—i.e. deposition, f>0 (dissolution, f<0)—then the calcium concentration increases (decreases) from the …
(PDF) Thin-film-induced morphological …
In fact, the deposition of calcite occurring while the film is flowing causes the average concentration of calcium to be progressively reduced from the initial concentrations at the source point. However, the film degassing …
Calcite Mineral | Uses and Properties
Calcite sand crystals: Calcite in the form of siliceous crystals from the Badlands, South Dakota. The calcite grew as crystals in a sand, including the sand grains within its crystal structure. Specimen is about five inches (twelve centimeters) across. More Minerals : Diamonds Do Not Form From Coal : Tourmaline :
Phosphate uptake by calcite: Constraints of concentration and …
— The main challenges are as follows: (i) calcite has a soluble mineral surface involved in dissolution and precipitation processes in solutions; (ii) Ca 2+ and CO 3 2− are released by calcite dissolution and Ca 2+ ions combine with PO 4 3− to form calcium phosphate precipitates, while CO 3 2−, as a base, has a strong impact on the ...
Synthesis of nanostructured calcite thin film by additive-free
— There is new development in nanostructured calcite research offering high potential sensitive application due to its non-toxic inorganic metal properties. Previous research revolves around calcium carbonate in powder form and mainly used as fillers in industry. However, nanostructured calcite thin film synthesis is lacking reports despite its …
Calcite Dissolution Kinetics | Aquatic Geochemistry
— We compare the canonical treatment of calcite's dissolution rate from the literature in a closed system, particle batch reactor, with the alternative approach …
Formation of amorphous calcium carbonate in …
— Speleothem deposits are among the most valuable continental formations in paleoclimate research, as they can be dated using absolute dating methods, and they also provide valuable climate proxies.
Calcite dissolution rates in seawater: Lab vs. in-situ …
— The non-linearity of Eq. (1) in seawater is consistent with the calcite surface transitioning through three dissolution mechanisms that become active at different critical saturations ("Ω critical s"): retreat of pre-existing steps for Ω = 1 to Ω critical ≈ 0.9, the opening of etch pits at defects for Ω ≈ 0.9 to Ω critical ≈ 0.75, and the opening of etch …
Formation and Structure of Calcium Carbonate …
Addition of Mg 2+ to the PAH ([PAH] = 20 μg mL –1)/ CaCl 2 ·2H 2 O reaction solution at a concentration of [Ca 2+] = [Mg 2+] = 10 mM led to the formation of ≈300 nm thick polycrystalline calcite films (Figure 7) that …
Removal of high-concentration phosphate by calcite: Effect …
— In this work, the removal of phosphate with or without added sulfate at various concentrations was studied at 48 h and at pH 4.5 or 13.0 (Fig. 3)pared to the results without the addition of sulfate at pH 4.5, low SO 4 2− /PO 4 3− ratios of 1.5 and 3.0 enhanced the removal of phosphate. Because sulfate increased dissolution of calcite …
6 Dissolution and Precipitation of Calcite: The Chemistry …
There is a tremendous amount of literature on calcite dissolution experiments performed with various materials (synthetic calcite, natural calcites and limestone) under various …
Calcium Carbonate Dissolution from the …
— Particles of calcite start to dissolve in environments where the ambient seawater carbonate ion concentration falls beneath the equilibrium carbonate ion concentration (which is elevated towards the …
The impact of evaporation to the isotope composition of DIC in calcite
— To understand the effects of processes that influence the stable carbon and oxygen isotope ratios of DIC in a small planar water film, two model approaches have been developed in the past, a ...
Magnesium Ions Direct the Solid‐State
— TEM and SAED also provided information about the structures of the Mg-calcite films. Recent studies of calcite optical lenses found in the brittlestar Ophiocoma wendtii containing 15 mol% Mg …
Fig. 4 TEM image (a) and SAED (b) of calcite ribbons after...
Calcite film coatings composed of nanoneedles can form on the surfaces of CA fibers while maintaining the fibrous and macroporous structures if the concentration of PAA is in a suitable range ...
Hydrogen adsorption on calcite mineral surface in the …
— Conversely, in a dry system, the entire calcite interface becomes accessible for hydrogen adsorption, resulting in comparatively higher adsorption values. Apart from this, the percentage decrease was consistent in all temperatures since the water-film concentration was kept constant at all temperature values. 3.6.
Factors controlling and influencing polymorphism, morphology and size
— They observed that calcite was formed at low concentrations of the reactants through the transformation of unstable phases, ACC, vaterite and aragonite, into stable calcite. ... that the absorption of CO 2 in a suspension of lime is accompanied and boosted by a fast reaction in the gas-liquid film [119, 153]. The use of gas mixtures has not a ...
Morphological Evaluation and Film Formation with Iso-Oriented Calcite
— However, the mixture of calcite and vaterite, the mixture of aragonite and calcite, pure calcite cryatals were produced when the concentration of imidazole were 50%, 60%, 70%, respectively; In the ...
Formation of Amorphous Calcium Carbonate Thin …
— A new and simple method for preparing large-area and continuous calcium carbonate films under mild conditions is described. Amorphous calcium carbonate (ACC) films have been formed both in …
Calcite dissolution rates in seawater: Lab vs. in-situ …
— We reconcile the offset between lab and in-situ rates by dissolving calcite in the presence of elevated orthophosphate (20 μm) and dissolved organic carbon (DOC) concentrations, where DOC is in the form of oxalic acid (20 μm), gallic acid (20 μm), and …
Biomimetic synthesis of calcite films by a …
At low concentration (o24 mM), Mg2+ modifies the habit to form calcite with a prismatic shape; while at higher concentrations, approaching that of seawater (51 mM), the calcite is mostly inhibited, thus enabling the …
Water Film Thickness in Unsaturated Porous Media: …
the film becomes thinner, the flushing efficiency of dissolved elements through the film decreases and the element concentration increases toward equilibrium concentration, leading to a slower dissolution rate in the film. The water film thickness on a single crystal of quartz, glass, calcite, and muscovite has been measured ex-
Nucleation in confinement generates long-range repulsion …
— Nevertheless, our calcite films remained intact and continuous throughout the SFA experiments, ... (SI) with respect to calcite and Ca 2+ concentration were calculated in the PhreeqC software, ...
6 Dissolution and Precipitation of Calcite: The Chemistry …
Experimental Methods of Calcite Dissolution 107 by Nernst (1904). It assumes that mass transport by molecular diffusion is essentially across a Nernst layer of thickness B, which has to be defined for each special case. For a first-order heterogeneous reaction at the surface, the flux Fe from the
Visualising the molecular alteration of the calcite (104) – …
— This film covers the crystal surface forming a layer that prevents direct interaction of ions ... (of which 40 Å in the z-direction is the calcite crystal), the ion concentration is approximately ...
Visualising the molecular alteration of the calcite (104) – …
— This film covers the crystal surface forming a layer that prevents direct interaction of ions and molecules with the calcite surface, for example reducing ... (of which 40 Å in the z-direction is the calcite crystal), the ion concentration is approximately 250 mM. We note that this concentration is considerably higher than that used in the XR ...
Origin and significance of ultra-slow calcite
— Pore fluid Sr concentrations tend to increase with depth and time due to calcite dissolution and precipitation (Fig. 1).The increase in pore fluid Sr occurs even if R net = 0, because primary biogenic calcite has Sr concentrations that are much higher than the equilibrium value with respect to seawater (Zhang et al., 2020).When biogenic …
Formation of amorphous calcium carbonate in …
— An innovative sampling and measurement protocol combined with scanning and transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy is presented,...
Formation of Thin Calcium Carbonate Films on Chitosan …
— Crystallization of two-dimensional spherulitic calcium carbonate films was performed on planar films of chitosan in the presence of poly(acrylic acid) (PAA). The …
Thin-film-induced morphological instabilities over calcite …
— In fact, the deposition of calcite occurring while the film is flowing causes the average concentration of calcium to be progressively reduced from the initial concentrations at the source point. However, the film degassing and the loss of calcium occur on longitudinal scales (greater than 10 cm ) much larger than the crenulation scale [ 7 ].
The impact of evaporation to the isotope composition of DIC in calcite
— 4. Kinetic fractionation and evaporation. When calcite precipitates from a thin film of drip water that is supersaturated with respect to calcite Ca 2+ and carbonate are removed from the solution and irreversibly incorporated into the calcite crystal lattice. During this process the concentration of DIC changes with some time dependent function C(t), …