Calcite Crystal Growth Research Articles

Design of a Synthetic Foldamer that Modifies the Growth of Calcite Crystals

An oligopyridine foldamer, whose structure is dictated by bifurcated hydrogen bonds, was designed to recognize the surface of calcite through three carboxylates, projected from one face of the molecule. At low concentrations of the trimer, elongated calcite crystals with angular, teeth-like growths, identified as {0l} faces, were exclusively formed. In the presence of a related monomer, only calcite rhombohedra are formed, indicating that it is the ordered array of carboxylates that causes the morphological changes, via a specific interaction between the foldamer and the newly expressed faces of the growing calcite crystals.

The nacre protein perlucin nucleates growth of calcium carbonate crystals.

Atomic force microscopy (AFM) in aqueous solution was used to investigate native nacre of the marine snail Haliotis laevigata on the microscopic scale and the interaction of purified nacre proteins with calcium carbonate crystals on the nanoscopic scale. These investigations were controlled by scanning electron microscopy (SEM), light microscopy (LM) and biochemical methods. For investigations with AFM and SEM, nacre was cleaved parallel to the aragonite tablets in this biogenic polymer/mineral composite. Multilamellar organic sheets consisting of a core of chitin with layers of proteins attached on both sides lay between the aragonite layers consisting of confluent aragonite tablets. Cleavage appeared to occur between the aragonite tablet layer and the protein layer. AFM images revealed a honeycomb-like structure to the organic material with a diameter of the 'honeycombs' equalling that of the aragonite tablets. The walls of the structures consisted of filaments, which were suggested to be collagen. The flat regions of the honeycomb-like structures exhibited a hole with a diameter of more than 100 nm. When incubated in saturated calcium carbonate solution, aragonite needles with perfect vertical orientation grew on the proteinacous surface. After treatment with proteinase K, no growth of orientated aragonite needles was detected. Direct AFM measurements on dissolving and growing calcite crystals revealed a surface structure with straight steps the number of which decreased with crystal growth. When the purified nacre protein perlucin was added to the growth solution (a super-saturated calcium carbonate solution) new layers were nucleated and the number of steps increased. Anion exchange chromatography of the water-soluble proteins revealed a mixture of about 10 different proteins. When this mixture was dialysed against saturated calcium carbonate solution and sodium chloride, calcium carbonate crystals precipitated together with perlucin leaving the other proteins in the supernatant. Thus perlucin was shown to be a protein able to nucleate calcium carbonate layers on calcite surfaces, and in the presence of sodium chloride, is incorporated as an intracrystalline protein into calcium carbonate crystals.

The influence of dissolved humic acids on the kinetics of calcite precipitation from seawater solutions

The influence of dissolved organic matter on the complex mechanism of calcite crystal growth from seawater was evaluated by a set of experiments at different humic acid concentrations (i.e. [HA]=50, 500, 1000 μg/kg) in NaCl–CaCl 2 solutions at a total ionic strength of 0.7 mol/kg. The temperature and P CO 2 of the experiments were maintained at 298 K and 40 Pa, respectively. The constant addition technique was used in order to maintain [Ca 2+] at ≅10.5 mmol/kg, while the [CO 3 2−] was varied to isolate its role on the precipitation rate. Assuming that the calcite precipitation in this solution is dominated by the reaction: (A1) Ca 2++ CO 3 2− ↔ k b k f CaCO 3 where k f and k b are the forward and reverse reaction rate constants, respectively, the net precipitation rate, R, can be described at any dissolved organic matter content by the difference between the forward and reverse rates: (A2) R=k f (a Ca 2+ ) n 1 (a CO 3 2− ) n 2 −k b or, in its logarithmic form: (A3) log(R+k b )− logK f +n 2 log[ CO 3 2−] where n i are the partial reaction orders with respect to the participating ions, a and γ are the ion activities and activity coefficients, respectively, and, K f= k f( a Ca 2+ ) n 1 ( γ CO 3 2− ) n 2 , a constant. Results of this study indicate that, similarly to seawater and NaCl–CaCl 2 solutions at the same ionic strength, the partial reaction order with respect to the carbonate ion concentration is 3, while the forward reaction rate constant, K f, decreases by one order of magnitude when the dissolved organic matter concentration increased from 0 to 1000 μg/kg. This suggests that the mechanism of calcite precipitation is independent of the dissolved organic matter concentration even if such a component inhibits the calcite precipitation rate. Applying our model to previous rate measurements carried out in seawater solution under the compositional condition [Ca 2+]≫[CO 3 2−], we found that the rate of calcite precipitation from seawater solutions, a complex function of P CO 2 and seawater inorganic inhibitors, still decreases as a function of the [HA] by at least one order of magnitude. Finally, we propose that the dissolved organic matter under the form of HA inhibits the calcite precipitation rate from seawater by covering the active growth sites rather than by complexation of calcium in solution.

Biomimetic nucleation and growth of CaCO 3 in hydrogels incorporating carboxylate groups

Poly-acrylamide hydrogels were modified by copolymerization with acrylic acid and used as growth medium for CaCO 3 in a double-diffusion arrangement. The carboxylate functionalities in the gel network facilitate the nucleation of a multitude of small crystallites of vaterite and calcite, which are temporarily stabilized even while supersaturation is increasing within the hydrogel. After an extended induction period the rapid spherulitic growth of calcite crystals along their c-axis is observed yielding spheres with diameters exceeding 300 μm. In the center of those aggregates disordered, porous regions can be identified as starting point of this rapid crystallization. The results are compared to previous studies on native poly-acrylamide hydrogels and networks modified with –SO 3H functional groups. The mineralization mechanism is significantly altered by specific interactions between the –COOH functionalized network and the evolving mineral phase.

Ca2+−Keggin Anion Colloidal Particles as Templates for the Growth of Star-Shaped Calcite Crystal Assemblies

The formation of star-shaped CaCO3 crystals by reaction of an aqueous solution of phosphotungstic acid and Ca2+ ions with CO2 is described. The phosphotungstate ions [(PW12O40)3- Keggin ions] complex with the Ca2+ ions in solution leading to the formation of highly uniform nanometer-sized colloidal particles of the salt, calcium phosphotungstate. Reaction of these nearly spherical colloidal particles with CO2 results in the growth of calcite with very regular, star-shaped morphology. Energy dispersive analysis of X-rays of the star-shaped calcite particles indicated the presence of the Keggin ions in the crystals suggesting that they play the role of nanoprecursors in the growth of calcite crystals with such unique morphology.

Self-organized formation of a hierarchical self-similar structure with calcium carbonate.

Self-organized growth of calcite crystals in a supersaturated solution with a gradual increase in the influence of silicate anions resulted in the formation of a hierarchical self-similar morphology consisting of three-pointed stars with sizes ranging from 100 nm to 100 micrometer.

X-ray absorption spectroscopy study of Cu 2+ and Zn 2+ adsorption complexes at the calcite surface : Implications for site-specific metal incorporation preferences during calcite crystal growth

We report results from in situ extended X-ray absorption fine structure (EXAFS) spectroscopy studies of Cu(II) and Zn(II) complexes forming at the calcite surface following adsorption from preequilibrated calcite-saturated solutions. Both Cu(II) and Zn(II) coordinate at Ca sites on the calcite surface, forming mononuclear inner-sphere adsorption complexes. The Zn adsorption complexes are in tetrahedral coordination with first-shell O neighbors with R Zn-O = 1.95 Å, and the Cu complexes are Jahn-Teller distorted, with equatorial R Cu-O = 1.95 Å. Results from EXAFS data of dilute Cu- and Zn-calcite solid solutions confirm substitution of these metals in the Ca site of the calcite structure as octahedral complexes during coprecipitation. X-ray fluorescence microanalyses of calcite (101̄4) hillocks grown in coprecipitation experiments show that divalent Cu and Zn, which have ionic radii smaller than Ca, are preferentially incorporated into the parallel arrays of <4̄41> + steps that define one pair of symmetrically equivalent vicinal faces on polygonized growth spirals. In contrast, other divalent metals with sixfold ionic radii smaller than Ca (Co, Cd, Mn, Mg) have been shown to be preferentially incorporated into <4̄41> − growth steps, which define the second pair of vicinal faces on the growth spirals, but which are symmetrically nonequivalent to the steps on the first pair. The distortion from octahedral symmetry observed for the Cu and Zn adsorption complexes likely plays a key role in the observed preference of Cu and Zn for incorporation into the <4̄41> + steps.

Nucleation and growth kinetics in synthesizing nanometer calcite

The size of nanometer particles uniquely depends not only on the nucleus growth rate but also on the nucleation rate. This paper presents the effect of sodium tripolyphosphate on the microimages, synthesis reaction, nucleation and growth during the synthesizing of nanometer calcite using chemical analysis, SEM technique and Rosin–Ramuler probability statistics theory. The result showed that the calcium hydroxide carbonation reaction was inhibited by sodium tripolyphosphate adsorbed on the active growth sites. The SEM images revealed that the synthesizing of nanometer calcite was a multi-stable state process. When [Na 5P 3O 10]=0, 38.04 μM, the tiny calcite nuclei re-dissolved and the nucleation rate was negative at the final stage. The supersaturation and the nucleation rate increased in proportion to the concentration of sodium tripolyphosphate. The presence of sodium tripolyphosphate accelerated the nucleation of calcite and inhibited the crystal growth. During the crystallization of nanoscale calcite, the fluctuation nucleation, nucleus growth and coarsening growth may take place in series for a fine particle. To a whole carbonation solution, these three steps may occur simultaneously. At the final stage of the nucleation, the calcite crystal growth was controlled by a short-range diffusion and an interface reaction. The Zener–Ham model could not correctly describe the crystal growth. At the coarsening growth stage, the Zener–Ham model could not correctly describe the crystal growth yet. Once the steady nucleus had been shaped in the solution, the crystal growth was determined by a long-range diffusion, and the growth process accorded with Zener–Ham model quite well.

Aligned Growth of Calcite Crystals on a Self-Assembled Monolayer

Aligned Growth of Calcite Crystals on a Self-Assembled Monolayer

Effects of acidic polysaccharide on crystal growth of calcite from coccolith of marine alga

Effects of acidic polysaccharide on crystal growth of calcite from coccolith of marine alga

The kinetics of carbonate scaling—application for the prediction of downhole carbonate scaling

Reliable prediction of calcium carbonate, CaCO 3, scaling for estimating scale production oilfield production wells and surface facilities requires both thermodynamic models to indicate the tendency for scaling from solution and kinetic models to predict the rate of scaling and thus the time required to cause blockage. The application of such models could contribute to field scale management and in the development of more effective treatments of carbonate scale during oilfield production. The performance of a kinetic model for calcium carbonate scaling rate based on the measurements of individual calcite crystal growth rates is tested against scale deposition in tube blocking experiments using synthetic formation brines under pressure and temperature levels. The profile of the scale formed on the internal surface of the tube during the experiments was measured and compared with the predicted results from the kinetic model. The application of the kinetic model to the prediction of carbonate scaling in a North Sea well has also been tested. The results from the model are in good agreement with the actual scale profile recorded in the tubing by a downhole multi-finger caliper (MFC) tool.

Calcite Crystal Growth Rate Inhibition by Polycarboxylic Acids

Calcite crystal growth rates measured in the presence of several polycarboxyclic acids show that tetrahydrofurantetracarboxylic acid (THFTCA) and cyclopentanetetracarboxylic acid (CPTCA) are effective growth rate inhibitors at low solution concentrations (0.01 to 1 mg/L). In contrast, linear polycarbocylic acids (citric acid and tricarballylic acid) had no inhibiting effect on calcite growth rates at concentrations up to 10 mg/L. Calcite crystal growth rate inhibition by cyclic polycarboxyclic acids appears to involve blockage of crystal growth sites on the mineral surface by several carboxylate groups. Growth morphology varied for growth in the absence and in the presence of both THFTCA and CPTCA. More effective growth rate reduction by CPTCA relative to THFTCA suggests that inhibitor carboxylate stereochemical orientation controls calcite surface interaction with carboxylate inhibitors.

Ovotransferrin is a Matrix Protein of the Hen Eggshell Membranes and Basal Calcified Layer

The eggshell is an highly ordered structure deposited in the distal oviduct and composed of calcium carbonate and an organic matrix which is believed to influence its fabric. We have identified ovotransferrin as an 80kDa matrix protein observed at high concentration in the uterine fluid at the initial stage of shell mineralization, by N-terminal sequencing and western blotting using monoclonal and polyclonal antibodies. It is present in extracts from demineralized eggshell and was localized by immunofluorescence in the eggshell membranes and mammillae, which are the sites of calcite nucleation. Northern blotting and RT-PCR demonstrated that ovotransferrin message was expressed in the proximal oviduct (magnum and white isthmus), and at a lower magnitude in the distal oviduct (red isthmus and uterus). Ovotransferrin was revealed by immunofluorescence in the tubular gland cells of the uterus. Calcium carbonate crystals grown in vitro in the presence of purified ovotransferrin showed large modifications of the calcite morphology. These observations and its presence in eggshell and membranes suggest a dual role for ovotransferrin, as a protein influencing nucleation and growth of calcite crystals and as a bacteriostatic filter to reinforce its inhibition of Salmonella growth in egg albumen.

Effect of Sulfate Content of Biomacromolecules on the Crystallization of Calcium Carbonate

ABSTRACTNatural composite bioceramics such as bone, teeth, carapaces and shells contain organic and inorganic moieties, with the organic matrix components directly involved in the precise formation of these structures. We have previously shown that chicken eggshell contains two main sulfated polymers (proteoglycans), referred to as mammillan and ovoglycan which are involved in nucleation and growth of the eggshell calcite crystals. They differ on their anionic properties due to the carboxylate and sulfate content of their glycosaminoglycan component. Based on biological and biochemical evidences, the putative role of mammillan, a keratan sulfate proteoglycan, is in the nucleation of the first calcite crystals, while that of ovoglycan, a dermatan sulfate proteoglycan, is to regulate the growth and orientation of the later forming crystals of the chicken eggshell. In this communication, a systematic study of the influence of variable concentrations of glycosaminoglycans differing in their sulfation status on the morphology, size and number of calcium carbonate crystals after crystallization on microbridges from a calcium chloride solution under an atmosphere of ammonium carbonate at different pH is presented. Depending on the pH and concentration, the variation of sulfation status drastically changed the morphology, size and number of calcite crystals. The produced calcite particles with various morphologies are promising candidates for some novel materials with desirable shape- and texture-depending properties.

Selection of a mineralizer from organic salt solutions for hydrothermal growth of calcite single crystals

Calcite single crystals with high purity and transparency, called Iceland spar, have been widely used for polarized devices. The artificial growth of calcite single crystals for these devices has been carried out by the hydrothermal method [1–12], TSSG (top-seeded solution growth) [13] and TSZM (travelling solvent zonemelting) technique [14, 15], using seed crystals. Both of the TSSG and TSZM techniques are based on the flux growth using Li2CO3 as a flux, which results in contamination of the grown crystals by Li. The hydrothermal method is the most suitable method to grow calcite crystals, because the dissociation of CO2 is suppressed under hydrothermal conditions and crystals with less thermal strains are grown at relatively low temperatures. The hydrothermal growth of calcite crystals has been carried out in the H2O-CO2 system [5, 6], or using inorganic salt solutions as a mineralizer, such as LiCl [1], NaCl [1, 9, 10], KCl [9], CaCl2 [1], NH4Cl [1], KNO3 [11], NaNO3 [11], Ca(NO3)2 [12], NH4NO3 [2, 3, 12], and K2CO3 [4]. However, the limited growth rate of calcite single crystals of up to 50 μm/day even under high temperature and high pressure hydrothermal conditions [4], obstructs the industrial production of calcite single crystals. The authors recently found that calcite crystals could be grown at high growth rate under mild hydrothermal conditions in an ammonium acetate solution, i.e. an organic salt solution [7, 8]. This result suggests the possibility of using other organic salt solutions as mineralizers for calcite crystal growth. In this paper, the solubility measurement and hydrothermal growth of calcite crystals were carried out in various organic salt solutions to find a suitable mineralizer for the hydrothermal growth of calcite crystals. The solubilities of calcite in various organic ammonium salt solutions were measured as described previously [16] and are shown in Table I. An autoclave lined with Hatelloy C with an inner volume of 12 cm3 was used for the measurements. The autoclave was equipped with a platinum mesh in the chamber to separate the solute from the solvent under hydrothermal conditions. A few pieces of cleaved natural single crystals of calcite (Iceland spar from Creel, Chihuahua, Mexico) were placed on the platinum mesh and one of the 0.1 M or 0.08 M organic ammonium salt solutions (60% fill ratio) was poured into the bottom of the autoclave after its pH was adjusted to 7.3 using aqueous ammonia. The contents of the autoclave were agitated at the desired temperature for 16 h by rotating the autoclave in an electric oven. After establishing the equilibrium, the rotation was stopped to separate the crystals from the solution under hydrothermal conditions, and then the autoclave was quenched into cold water. The solubility was determined from the weight difference of the crystals before and after the hydrothermal treatment. The results of the solubility measurements of calcite at 200 ◦C in various organic salt solutions (0.1 M), are summarized in Table I. After the hydrothermal treatment, a few solutions became black in color, which suggested that these organic salts decomposed under hydrothermal conditions. In general, calcite dissolves in ammonium mono-carboxylate solutions, although the solubility is lower than in the ammonium nitrate solution, an inorganic salt solution. The ammonium lactate and glutamate solutions gave high solubilities of calcite. The solubilities of calcite in ammonium monocarboxylate solutions (0.08 M) were measured up to

The effect of benzotriazoles on calcium carbonate scale formation

Benzotriazoles have been used satisfactorily for the last 25 years as a corrosion inhibitor for copper pipelines. The effect of six benzotriazoles on the crystal growth of calcite was investigated at sustained supersaturation. The rates of crystal growth measured in the presence of benzotriazoles at concentrations of 7.5×10 −5 M were drastically increased. The apparent order of the reaction found from kinetic data was n=2±0.2, thus suggesting a surface diffusion controlled mechanism.

Skeletal aragonite neomorphism in Plio-Pleistocene sandy limestones and sandstones, Hollywood, Florida, USA

Abstract The basic mechanics of the neomorphism of aragonitic shells to calcite are generally understood, but fundamental questions remain concerning the details of the process. Completely and partially neomorphosed aragonitic skeletal fragments recovered in cores of Plio-Pleistocene limestones and sandstones from Hollywood, Florida, provide some insights into the process. Skeletal aragonite neomorphism occurred in a volume for volume manner across solution films, which resulted in the preservation of ghosts of fine-scale microstructures. Neomorphic calcite crystals that replaced skeletal aragonite in at least some instances inherited their crystallographic orientation from adjoining calcite cement crystals rather than from the host shell microstructure. Some neomorphic calcite crystals inherited the optical orientation of nearby echinoderm ossicles. However, host shell microstructure commonly controlled the direction of migration of the neomorphic replacement front. Anisotropies in shell solubility influenced the directional rates of growth of neomorphic calcite crystals, as evidenced by the strong tendency for the boundaries between neomorphic calcite and aragonite to parallel or coinicide with shell microstructural features. No examples were observed where neomorphic calcite replaced aragonite along euhedral crystal faces, such as commonly occurs during dolomitization and the replacement of limestone by megaquartz.

An assessment of calcite crystal growth mechanisms based on crystal size distributions

Calcite crystal growth experiments were undertaken to test a recently proposed model that relates crystal growth mechanisms to the shapes of crystal size distributions (CSDs). According to this approach, CSDs for minerals have three basic shapes: (1) asymptotic, which is related to a crystal growth mechanism having constant-rate nucleation accompanied by surface-controlled growth; (2) lognormal, which results from decaying-rate nucleation accompanied by surface-controlled growth; and (3) a theoretical, universal, steady-state curve attributed to Ostwald ripening. In addition, there is a fourth crystal growth mechanism that does not have a specific CSD shape, but which preserves the relative shapes of previously formed CSDs. This mechanism is attributed to supply-controlled growth. All three shapes were produced experimentally in the calcite growth experiments by modifying nucleation conditions and solution concentrations. The asymptotic CSD formed when additional reactants were added stepwise to the surface of solutions that were supersaturated with respect to calcite (initial Ω = 20, where Ω = 1 represents saturation), thereby leading to the continuous nucleation and growth of calcite crystals. Lognormal CSDs resulted when reactants were added continuously below the solution surface, via a submerged tube, to similarly supersaturated solutions (initial Ω = 22 to 41), thereby leading to a single nucleation event followed by surface-controlled growth. The Ostwald CSD resulted when concentrated reactants were rapidly mixed, leading initially to high levels of supersaturation (Ω >100), and to the formation and subsequent dissolution of very small nuclei, thereby yielding CSDs having small crystal size variances. The three CSD shapes likely were produced early in the crystallization process, in the nanometer crystal size range, and preserved during subsequent growth. Preservation of the relative shapes of the CSDs indicates that a supply-controlled growth mechanism was established and maintained during the constant-composition experiments. CSDs having shapes intermediate between lognormal and Ostwald also were generated by varying the initial levels of supersaturation (initial Ω = 28.2 to 69.2) in rapidly mixed solutions. Lognormal CSDs were observed for natural calcite crystals that are found in septarian concretions occurring in southeastern Colorado. Based on the model described above, these CSDs indicate initial growth by surface control, followed by supply-controlled growth. Thus, CSDs may be used to deduce crystal growth mechanisms from which geologic conditions early in the growth history of a mineral can be inferred. Conversely, CSD shape can be predicted during industrial crystallization by applying the appropriate conditions for a particular growth mechanism.

The effect of barium on calcite {10 [formula omitted]4} surfaces during growth

In situ atomic force microscopy (AFM) experiments have provided information about the effect of Ba 2+ on crystal growth of calcite {10 1 4} surfaces. The microtopographic features observed have been interpreted by considering both the structural control that the calcite surfaces exert on the incorporation of divalent cations and the supersaturation state of the solution used. Pinning of the calcite growth steps occurs at low Ba concentrations, suggesting specific sites for Ba incorporation. When the Ba content of the solution is increased the advancement of monomolecular steps is observed. Although [ 4 41] + and [48 1 ] + steps advance showing characteristic jagged edges, the parallel steps (i.e., [ 4 41] − and [48 1 ] −) remain practically immobile. This fact can be explained by considering the nonsymmetrically related distribution of large and small sites along the calcite steps and the easier incorporation of barium on the former. The measured increase in the height of the newly grown steps is also consistent with such preferential incorporation of Ba in certain positions. A further increase in the Ba concentration of the solutions leads to the formation of bidimensional nuclei on the calcite {10 1 4} surfaces. The nature of these nuclei is discussed taking into account the supersaturation of the solution with respect to two possible structures that can accommodate Ba: the calcite-type structure and the aragonite-type structure.

Calcite crystal growth inhibition by humic substances with emphasis on hydrophobic acids from the Florida Everglades

The crystallization of calcium carbonate minerals plays an integral role in the water chemistry of terrestrial ecosystems. Humic substances, which are ubiquitous in natural waters, have been shown to reduce or inhibit calcite crystal growth in experiments. The purpose of this study is to quantify and understand the kinetic effects of hydrophobic organic acids isolated from the Florida Everglades and a fulvic acid from Lake Fryxell, Antarctica, on the crystal growth of calcite (CaCO 3). Highly reproducible calcite growth experiments were performed in a sealed reactor at constant pH, temperature, supersaturation (Ω = 4.5), P CO 2 (10 −3.5atm), and ionic strength (0.1 M) with various concentrations of organic acids. Higher plant-derived aquatic hydrophobic acids from the Everglades were more effective growth inhibitors than microbially derived fulvic acid from Lake Fryxell. Organic acid aromaticity correlated strongly with growth inhibition. Molecular weight and heteroatom content correlated well with growth inhibition, whereas carboxyl content and aliphatic nature did not.