Supersaturated Calcium Carbonate Solution Research Articles

Precipitation of Calcium Carbonate (CaCO3) in Water–Monoethylene Glycol Solutions

The influence of monoethylene glycol (MEG) on the precipitation process of calcium carbonate at constant supersaturation, 25 °C, and pH 8.5 was investigated. MEG aqueous solutions supersaturated with respect to all calcium carbonate polymorphs were used since they are often encountered in oil production processes where they are used as a hydrate inhibitor. Both seeded and unseeded experiments were done in aqueous supersaturated calcium carbonate solutions containing MEG over the concentration range 0–80% v/v. The presence of MEG affected the induction times and the subsequent rates of precipitation in unseeded, spontaneous precipitation of calcium carbonate. At low values of the supersaturation ratio (SRcalcite = 77.62–15 135.61 or σcalcite = 7.81–122) and for MEG concentrations in the range 30–80% v/v, the solutions were stable for 4 days. At lower than 30% v/v MEG concentrations, calcium carbonate precipitation took place past induction periods between 160 and 500 min. The morphological examination of the precipitates showed that in the presence of low MEG concentrations (10–20% v/v) the precursor vaterite was stabilized. The homogeneous nucleation and growth of calcium carbonate in the absence and in the presence of MEG was also investigated by the inoculation of stable supersaturated solutions with quartz and calcite seed crystals. In both cases nucleation and growth of calcium carbonate was significantly reduced with increasing MEG concentration in the solutions.

Supersaturated calcium carbonate solutions are classical.

Mechanisms of CaCO3 nucleation from solutions that depend on multistage pathways and the existence of species far more complex than simple ions or ion pairs have recently been proposed. Herein, we provide a tightly coupled theoretical and experimental study on the pathways that precede the initial stages of CaCO3 nucleation. Starting from molecular simulations, we succeed in correctly predicting bulk thermodynamic quantities and experimental data, including equilibrium constants, titration curves, and detailed x-ray absorption spectra taken from the supersaturated CaCO3 solutions. The picture that emerges is in complete agreement with classical views of cluster populations in which ions and ion pairs dominate, with the concomitant free energy landscapes following classical nucleation theory.

Modification of CaCO3 precipitation rates by water-soluble nacre proteins

Mineral growth in nacre and other CaCO3-containing biominerals is controlled by biopolymers. Water-soluble proteins were extracted from nacre of the sea snail Haliotis laevigata by dissolving the mineral phase with 6% acetic acid. The influence of this protein mixture on CaCO3 precipitation rates was investigated at different concentrations. A well-established assay for measuring the pH-value during CaCO3 precipitation with and without protein additives was extended by calculating maximum precipitation rates from the pH-values. It could be shown that precipitation rates are greatly influenced by the mixtures of water-soluble nacre proteins. At very low protein concentrations (0.02μg/ml) a rate enhancement in comparison to the pure supersaturated calcium carbonate solution by a factor of 1.4 was observed. At higher protein concentrations, a strong inhibitory effect occurred, with total inhibition at concentrations of 1.0μg/ml and higher. Two unspecific proteins (bovine serum albumin and lysozyme) showed little or no modification of precipitation rates. In vivo, the function of the strong inhibition of CaCO3 precipitation by nacre proteins at higher concentrations is presumably to prevent uncontrolled crystallization in the extrapallial fluid. The rate-enhancing capability of proteins at low concentrations may be explained by the presence of acidic and/or hydrophilic moieties.

Perlinhibin, a Cysteine-, Histidine-, and Arginine-Rich Miniprotein from Abalone ( Haliotis laevigata) Nacre, Inhibits In Vitro Calcium Carbonate Crystallization

We have isolated a 4.785 Da protein from the nacreous layer of the sea snail Haliotis laevigata (greenlip abalone) shell after demineralization with acetic acid. The sequence of 41 amino acids was determined by Edman degradation supported by mass spectrometry. The most abundant amino acids were cysteine (19.5%), histidine (17%), and arginine (14.6%). The positively charged amino acids were almost counterbalanced by negatively charged ones resulting in a calculated isoelectric point of 7.86. Atomic-force microscopy studies of the interaction of the protein with calcite surfaces in supersaturated calcium carbonate solution or calcium chloride solution showed that the protein bound specifically to calcite steps, inhibiting further crystal growth at these sites in carbonate solution and preventing crystal dissolution when carbonate was substituted with chloride. Therefore this protein was named perlinhibin. X-ray diffraction investigation of the crystal after atomic-force microscopy growth experiments showed that the formation of aragonite was induced on the calcite substrate around holes caused by perlinhibin crystal-growth inhibition. The strong interaction of the protein with calcium carbonate was also shown by vapor diffusion crystallization. In the presence of the protein, the crystal surfaces were covered with holes due to protein binding and local inhibition of crystal growth. In addition to perlinhibin, we isolated and sequenced a perlinhibin-related protein, indicating that perlinhibin may be a member of a family of closely related proteins.

Perlwapin, an Abalone Nacre Protein with Three Four-Disulfide Core (Whey Acidic Protein) Domains, Inhibits the Growth of Calcium Carbonate Crystals

We have isolated a new protein from the nacreous layer of the shell of the sea snail Haliotis laevigata (abalone). Amino acid sequence analysis showed the protein to consist of 134 amino acids and to contain three sequence repeats of ∼40 amino acids which were very similar to the well-known whey acidic protein domains of other proteins. The new protein was therefore named perlwapin. In addition to the major sequence, we identified several minor variants. Atomic force microscopy was used to explore the interaction of perlwapin with calcite crystals. Monomolecular layers of calcite crystals dissolve very slowly in deionized water and recrystallize in supersaturated calcium carbonate solution. When perlwapin was dissolved in the supersaturated calcium carbonate solution, growth of the crystal was inhibited immediately. Perlwapin molecules bound tightly to distinct step edges, preventing the crystal layers from growing. Using lower concentrations of perlwapin in a saturated calcium carbonate solution, we could distinguish native, active perlwapin molecules from denaturated ones. These observations showed that perlwapin can act as a growth inhibitor for calcium carbonate crystals in saturated calcium carbonate solution. The function of perlwapin in nacre growth may be to inhibit the growth of certain crystallographic planes in the mineral phase of the polymer/mineral composite nacre.

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.

Control of crystal morphologyvia molecular imprinting

Imprinted polymers were prepared from divinylbenzene and 6-methacrylamidohexanoic acid as the functional monomer, using calcite crystals of three different morphologies as templates. After template removal voids in the polymer remained which reflected the size and shape of the template crystals. The use of these imprinted polymers in aqueous supersaturated calcium carbonate solution resulted in the formation of some crystal objects of unusual morphology. In the case of spheroidal imprints, the nucleated crystals grow via the {104} faces in many directions creating clusters whose surface consists of many small rhombohedral crystallites. However, in the case of rhombohedral imprints, no conflict between crystal growth and the constraints of nucleation at the polymer surface arises and the new crystals very closely resemble the templates. © 2001 Society of Chemical Industry

The Influence of Particulates on CaCO3 Scale Formation

The work reported here is based on an experimental investigation of the effect of well-defined commercial calcium carbonate particles and silica nanoparticles on the deposition rate and morphology of deposits, formed during the flow of a solution supersaturated with respect to CaCO 3 . The term combined shall be used for such runs. The effect of the above particles on the spontaneous precipitation in a supersaturated calcium carbonate solution is also examined. Isothermal conditions are maintained in all the tests

Influence of the Chitosan Surface Profile on the Nucleation and Growth of Calcium Carbonate Films

Calcium carbonate crystal growth on a chitosan substrate was achieved using a supersaturated calcium carbonate solution. Heterogeneous nucleation of the calcium carbonate crystals was significantly...

Chitosan-calcium carbonate composites by a biomimetic process

The crystal growth of calcium carbonate on a chitosan substrate was achieved using a supersaturated calcium carbonate solution, by using various additives, such as 6-aminocaproic acid (6AA) and polyacrylic acid (PAA). Polyacrylic acid modified the chitosan-film surface and promoted the nucleation of calcium carbonate crystals. In the absence of polyacrylic acid, sporadic nucleation and crystallization was observed via optical microscopy. By introducing polyacrylic acid into the systems, positively charged protonated nitrogen and negatively charged carboxylate ions were produced by reaction between the amino group in the chitosan and carboxyl group in polyacrylic acid, which were detected by ATR-IR and XPS techniques. These charges induced the nucleation of the calcium carbonate crystals, calcite and vaterite, on the chitosan-film surface. In this case, the crystals showed spherical morphology, which consisted of a large number of small particles with a diameter of about 0.2 μm. The calcium carbonate crystals growing on the rigid chitosan-film surfaces are uniform.

Synthesis of calcium carbonate–chitosan composites via biomimetic processing

AbstractThe crystal growth of calcium carbonate on a chitosan substrate was achieved using a supersaturated calcium carbonate solution, at different concentrations of polyacrylic acid (PAA) as an additive. Several techniques have been employed to characterize the systems. The pH of the solution as the one of indices was used to monitor the crystallization. In the absence of polyacrylic acid, the pH of the solution changed from 6.00 to 8.50 during the crystallization; meanwhile, sporadic nucleation and crystallization was observed via optical microscopy. By introducing polyacrylic acid to the systems, positively charged protonated nitrogen and negatively charged carboxylate ions were produced by reaction between the amino group in chitosan and the carboxyl group in polyacrylic acid, which were detected by ATR‐IR and XPS techniques. These charges induced calcium carbonate nucleation of calcite and vaterite crystals on the chitosan‐film surface. The average size of the vaterite phase was about 15 nm, determined by XRD. The pH of the solution changed from 5.80 to 9.25 during the crystallization; moreover, the crystals showed spherical morphology, which consisted of a large number of small particles with a diameter of about 0.2 μm. © 1995 John Wiley & Sons, Inc.

Inhibition of the growth of calcium carbonate crystals by multiple lectins in the coelomic fluid of the acorn barnacle Megabalanus rosa

The interaction between the multiple lectins (BRA-2, BRA-3) in the coelomic fluid of the acorn barnacle Megabalanus rosa and calcium ions was studied by ultraviolet difference spectroscopy. The association constants for BRA-2 and BRA-3 were 1.4 × 10 4 M −1 and 2.2 × 10 4 M −1 at pH 8.0, respectively. Multiple lectins inhibited the crystal growth of supersaturated calcium carbonate solution at a lectin concentration of > 0.1 mg/30 ml. Destruction of the carbohydrate-recognition domains of the lectins decreased the inhibitory activities on the crystal growth. Incorporation of BRAs into the crystal was demonstrated using FITC-labeled lectins.

Canine bile contains anticrystallization factors that inhibit precipitation of calcium carbonate

Previous studies have strongly suggested that human bile contains a substance(s) that interferes with the precipitation of calcium phosphate and carbonate from solution. These studies, however, did not distinguish between calcium binding by biliary constituents resulting in decreased calcium carbonate saturation (alterations in solution thermodynamics) and true inhibition of calcium salt precipitation by kinetic factors. Because our recent studies have shown that canine common duct bile is always supersaturated with calcium carbonate (thermodynamically at risk for precipitation), we hypothesized that it must contain kinetic factors that inhibit formation and/or growth of calcium carbonate crystals. Effects of canine bile, bovine albumin and the bile salt taurocholate on calcium carbonate precipitation were studied in highly supersaturated solutions of calcium carbonate that spontaneously undergo rapid precipitation. Measured free ionized calcium concentrations, [Ca++], and calculated calcium carbonate saturation indices were compared in test solutions and controls to evaluate the thermodynamic effects of test solutions on the degree of saturation in the assay system. It is shown that addition of only 0.2 ml of normal canine gallbladder bile to the assay system (a 1:101 dilution of biliary components) abolished precipitation. A lesser inhibitory effect (a decrease in the rate of precipitation) was observed when gallbladder bile was diluted but was lost after 10-fold dilution. Canine common duct bile caused a decrease in the rate of precipitation similar to diluted gallbladder bile. In contrast, sodium taurocholate (250 mmol/L), the major bile salt in the dog, and albumin (1.5 gm/L), the most abundant protein in bile, had only a minimal inhibitory effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Canine bile contains anticrystallization factors that inhibit precipitation of calcium carbonate*1, *2

Previous studies have strongly suggested that human bile contains a substance(s) that interferes with the precipitation of calcium phosphate and carbonate from solution. These studies, however, did not distinguish between calcium binding by biliary constituents resulting in decreased calcium carbonate saturation (alterations in solution thermodynamics) and true inhibition of calcium salt precipitation by kinetic factors. Because our recent studies have shown that canine common duct bile is always supersaturated with calcium carbonate (thermodynamically at risk for precipitation), we hypothesized that it must contain kinetic factors that inhibit formation and/or growth of calcium carbonate crystals. Effects of canine bile, bovine albumin and the bile salt taurocholate on calcium carbonate precipitation were studied in highly supersaturated solutions of calcium carbonate that spontaneously undergo rapid precipitation. Measured free ionized calcium concentrations, [Ca++], and calculated calcium carbonate saturation indices were compared in test solutions and controls to evaluate the thermodynamic effects of test solutions on the degree of saturation in the assay system. It is shown that addition of only 0.2 ml of normal canine gallbladder bile to the assay system (a 1:101 dilution of biliary components) abolished precipitation. A lesser inhibitory effect (a decrease in the rate of precipitation) was observed when gallbladder bile was diluted but was lost after 10-fold dilution. Canine common duct bile caused a decrease in the rate of precipitation similar to diluted gallbladder bile. In contrast, sodium taurocholate (250 mmol/L), the major bile salt in the dog, and albumin (1.5 gm/L), the most abundant protein in bile, had only a minimal inhibitory effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium Carbonate Scale Formation on Heated Metal Surfaces

Geothermal water utilization is seriously hindered by the development of insoluble calcium carbonate formation. The nature of the polymorphs formed is strongly dependent on the solution conditions and the substrate on which scale is deposited. The employment of a flow-system in which supersaturated calcium carbonate solutions flowed through pipe specimens made of various materials such as 316 stainless steel or aluminum, and heated externally at temperatures ranging from 50°C to 80°C, revealed that the salt formed initially on the pipe walls was vaterite. Surface energies computed from kinetics data showed an increase with temperature from 36.7 to 59.2 mJ m -2. The activation energy was found to be 36 kJ mole -1 suggesting a surface controlled mechanism.

Inability to demonstrate calcite precipitation by bacterial isolates from travertine

Abstract Bacteria were isolated from 10 actively depositing travertine sites in Europe and North America. Forty‐four isolates were characterized and 33 (75%) were identified as Pseudomonas. Thirty isolates produced base on glucose‐peptone media and 32 isolates produced ammonia from amino acids. Because of the low bacterial biomass in the travertines, the formation of bases, including ammonia was not considered to be significant in carbonate precipitation. None of the bacteria was observed to precipitate calcite from supersaturated calcium carbonate solutions in vitro.

Pancreatic stone protein, a phosphoprotein which inhibits calcium carbonate precipitation from human pancreatic juice

A soluble protein isolated from human pancreatic stones, and present in pancreatic secretion, strongly inhibits precipitation from supersaturated calcium carbonate solutions. Therefore, we suggest that this new secretory protein may act as an inhibitor of spontaneous calcium carbonate precipitation from supersaturated pancreatic juice.

Crystallization of calcium carbonate in the presence of trace concentrations of phosphorus-containing anions: I. Inhibition by phosphate and glycerophosphate ions at pH 8.8 and 25°C

Addition of glycerophosphate ion or orthophosphate ion to a metastable supersaturated calcium carbonate solution greatly reduced the rate of calcite seeded crystal growth at 25°C. Crystallization rate constants were decreased to half their value in pure solutions by a glycerophosphate concentration of 1.6 x 10 -5M or an orthophosphate concentration of 2 x 10 -6M. A relationship between the crystallization rate constant and the additive ion concentration of either ion follows an expression based on a simple Langmuir-type adsorption model. This relationship suggests that calcite growth inhibition by phosphorus-containing anions involves blockage of crystal growth sites on the calcite surface.

Calcite crystal growth inhibition by phosphonates

Addition of several phosphonic acid derivatives to a supersaturated calcium carbonate solution greatly reduces the rate of growth of calcite seed crystals at 25°C. The mechanism of the inhibition by phosphonates appears to involve blockage of crystal growth sites on the calcite surface. The results indicate that phosphonic acid derivatives may be useful in preventing scale formation in evaporative desalination processes.

The crystallization of calcium carbonate. II. Calcite growth mechanism

Stable supersaturated solutions of calcium carbonate have been prepared at 10, 25, and 40°C by careful control of experimental conditions. Upon the addition of seed crystals of calcite, the crystallization kinetics have been followed by monitoring the calcium and hydrogen ion concentrations. After an initial growth surge, the process follows the kinetic equation established previously in which the rate of crystallization is proportional to the product of the concentrations, [Ca +2][CO 3 −2]. The activation energy for crystal growth is 11.0 ± 1.0 kcal mole −1, and the rate is independent of the stirring rate. Photomicrographic evidence is presented in support of the suggestion that the initial surge in the growth curves results from additional nucleation at the surface of the added calcite crystals and in the bulk of the supersaturated solution.