— 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 ...

 — 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 ].

 — 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 …

 — 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 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 ...

 — 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 …

 — 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).Compared 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 …

On a more domestic front, calcite is the mineral that dissolves to form the 'hard' water (water with high concentrations of dissolved ions) present in many Upper Midwest communities. In homes without water softeners, calcite can precipitate from calcium-rich groundwater to plug plumbing or form a crust below dripping faucets.

 — 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 ...

 — 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 …

 — 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), …

 — In this study, we conducted experiments on the transformation from calcite to protodolomite using bacteria. The surface dolomitization of calcite seed crystals was initiated by Vibrio harveyi J4, a newly isolated extreme halophilic bacterium, under increasing magnesium concentrations of 0, 0.05, 0.10, 0.15, to 0.20 mol L –1.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.

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

of the annealed films can be controlled according to the mag-nesium content of the ACC precursor, and pure aragonite films comprising single crystal domains are formed at very low mag-nesium concentrations. With the ability to characterize the thin films using transmission electron microscopy (TEM), these

 — 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 ...

DOI: 10.1016/J.CEJ.2014.04.037 Corpus ID: 93409289; Synthesis and application of magnesium amorphous calcium carbonate for removal of high concentration of phosphate @article{Xu2014SynthesisAA, title={Synthesis and application of magnesium amorphous calcium carbonate for removal of high concentration of phosphate}, author={Nan Xu and …

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 …

 — A) Bright‐field TEM image and B) corresponding SAED pattern of a single crystal domain in dolomite film generated from ACC films prepared at [Ca²⁺] = 10 × 10⁻³ m and [Mg²⁺] = 100 × 10 ...

 — 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 …

 — The calcite films thus grown within days or weeks varied in thickness but typically were polycrystalline and epitaxial: a variety of morphologies and surface features are recorded. ... In uncoated samples the portlandite crystal dissolves in the aqueous phase and the corresponding rise in calcium concentration is monitored as a function of time ...

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 :

 — 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 …

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 …

There is a tremendous amount of literature on calcite dissolution experiments performed with various materials (synthetic calcite, natural calcites and limestone) under various …

 — As the water reacts with calcite, CO2 concentration decreases while HCO 3 ... mass transfer of the Ca 2+, HCO 3 − and CO 2 molecules through the diffuse film layer around the calcite particles [14, 15]; the models from these two papers are hereafter referred to as Yamauchi model [15] and Letterman model [14] respectively. When one of …

 — Using recent data on calcite dissolution and precipitation by Plummer et al., the deposition of CaCO 3 from thin films of supersaturated solutions of H 2 O/1bCO 2 /1bCaCO 3 to a CaCO 3 surface is calculated. The results are compared to previous calculations by Dreybrodt, which were based on precipitation kinetics as proposed by …

 — 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, ...

 — A further increase in Mg concentration (Mg/Ca > 0.5) resulted in uniform calcite crystals exhibiting faces with rough texture, slightly oblique to the c-axis of calcite (Fig. 9 c and d). Morphological analyses and computer simulations showed that these new faces formed an angle of 5–14° with respect to the c -axis, which roughly corresponds ...

 — Behavior and characteristics of amorphous calcium carbonate and calcite using CaCO 3 film synthesis. Author links open overlay panel Seung-Woo Lee a, Yong-Jae Kim b, Yun-Hee Lee b ... The supersaturation from Ca rich concentration in the experimental condition could influence a sequential phase transition of CaCO 3 [17]. …