Formation Of Vaterite Research Articles

Comparative Study on the Sand Bioconsolidation through Calcium Carbonate Precipitation by Sporosarcina pasteurii and Bacillus subtilis

To investigate potential implications of microbial activity on sand bioconsolidation and subsurface environments, two ureolytic strains, Sporosarcina pasteurii and Bacillus subtilis were tested for the production of calcium carbonate (CaCO3). Laboratory experiments with monoculture S. pasteurii (column 1) and coculture S. pasteurii-B. subtilis (column 2) were conducted to determine urea and calcium chloride reactivity and volumetric carbonate formation. Both columns were able to consolidate sand, whereas, column 1 induced greater CaCO3 precipitation. X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed two columns with different mineralogy with calcite, and vaterite formation. Column 1 showed rhombohedral and trigonal crystals morphology, whereas column 2 developed the prismatic calcite and the spherulite vaterite crystals might be due to the differences of the micro-environment caused by the urease expression of these bacterial species. These results indicate the possibility of using those crystals to cement loose sand whereas, highlighted the importance of combining these techniques to understand the geomicrobiology found in the subsurface environments.

Crystallization of calcium carbonate mineral with hierarchical structures regulated by silk fibroin in microbial mineralization system

In this work, we provide a novel idea to introduce silk fibroin (SF) into the microbial mineralization system and study the mechanism of mineralization of calcium carbonate by changing the mineralizing time and SF concentration. CaCO3 superstructures with complex forms and hierarchical surface textures were obtained in the presence of SF as a crystal growth modifier in the microbial mineralization system. Moreover, with the prolonged reaction time, the shape of CaCO3 in the additive-free mineralized system changes from a rough spherical to a smooth one, and then to a complex cube-like crystals. Surprisingly, superstructures CaCO3 crystals with smooth hemispheres were obtained in low concentrations of SF. An emergent self-organization process and its combination with an aggregated mechanism have been proposed for the formation of the complex hemispherical superstructure with numerous fish-like flakes on the surface in high concentrations of SF. What’s more, we found that high SF concentration is favorable for the formation of vaterite. The above results imply that the specific biomimetic synthesis strategy in the microbial mineralization system can provide a useful pathway to produce inorganic or inorganic-organic hybrid materials with a unique shape and specific textures.

The influence of CO2 accelerated carbonation on alkali‐activated fly ash cement under elevated temperature and pressure

AbstractAn alternative of wellbore cement system, formed through alkali‐activation of fly ashes also knows as fly ash geopolymers, provides attractive properties due to its high compressive strength and durability against acidic conditions. However, changes in microstructure and mineralogical during accelerated carbonation affected by CO2 alteration under elevated temperature and pressure have not been fully understood. This paper investigates and characterizes the alkali‐activated binders fly ash based in the acidic environment under elevated temperature and pressure. The results found that scales such a layer was formed in the gel phase at the spherical surface of fly ash after carbonation process. The effect is that the surface of the gel phase became rough and porous. Carbonate and/or bicarbonate salts were identified as major phase in the sample after immersion test. In the activated fly ash cement, both calcium aluminate silicate hydrate (C–A–S–H) and sodium aluminosilicate hydrate (N–A–S–H) gels were formed; C–A–S–H gel was decalcified, forming calcium carbonate phase in the form of calcite, aragonite or vaterite. These findings were confirmed by the analysis and identification of Fourier‐transformed infrared spectroscopy, X‐ray diffraction and scanning electron microscopy tests on the changes in the cement system.

Ab Initio Thermodynamics of Hydrated Calcium Carbonates and Calcium Analogues of Magnesium Carbonates: Implications for Carbonate Crystallization Pathways

Formation of calcium carbonate and its hydrates are important for a wide variety of geological, biological, and technological concerns. Recent studies have determined that formation of anhydrous crystalline calcite, aragonite, and vaterite can involve a complex series of nonclassical pathways in which the hydrated polymorphs monohydrocalcite (CaCO3·H2O), ikaite (CaCO3·6H2O), and amorphous calcium carbonate (ACC) play key roles and in some instances are stable or metastable endproducts. The stages of nucleation and crystallization along these pathways are not well understood, nor is how what is learned in an aqueous environment transfers to CO2-rich conditions. In this work ab initio thermodynamics based on density-functional theory and experimental chemical potentials for H2O-rich and CO2-rich systems are used to determine the stability of calcium carbonate polymorphs as a function of environmental conditions. In water-saturated supercritical CO2, formation of ikaite and monohydrocalcite are both highly e...

Fabrication of Uniform Casein/CaCO3 Vaterite Microspheres and Investigation of Its Formation Mechanism

Uniform Casein/CaCO3 microspheres were fabricated with well tuned properties and the formation mechanism based on the templating effect of casein micelles was proposed. In bone tissue engineering, vaterite microspheres were promising because of the biocompatibility and easy fabrication. Here Casein/CaCO3 microspheres were precipitated by mixing CaCl2 and Na2CO3 solutions under stirring in the presence of casein. All samples were mainly in vaterite, composed of aggregates of nanosized crystals. With the increase of casein concentration, the amount of calcite and microsphere size decreased while the loading content of casein increased, suggesting that casein induced the formation of vaterite and also stabilized the crystal phase. The formation mechanism was further investigated. With the increase of CaCl2 amount, the size of the forming microspheres increased while the zeta potential was stabilized, the polycrystalline nature was shown, and the presence of Ca inside microspheres was confirmed. Hence, the fo...

Vaterite induced by Lysinibacillus sp. GW-2 strain and its stability.

Studies on the formation and stability of vaterite by bacteria in experimental systems are of great importance for understanding the mechanism by which microbes contribute to carbonate mineralization. In this study, mineralization experiments using Lysinibacillus sp. strain GW-2 were carried out for 72h under shaking conditions and aging experiments using biotic and chemically synthesized vaterite were performed for 60days in distilled water and air. Our results indicate that Lysinibacillus sp. strain GW-2 can induce the formation of vaterite with spherical morphology from an amorphous calcium carbonate precursor. Biogenic vaterite was more stable than chemically synthesized vaterite in distilled water, perhaps due to organic matter secreted by bacteria that enwrapped the vaterite and prevented it from transforming into more stable phases. Infrared spectrophotometry of biogenic and chemically synthesized vaterite confirmed the presence of organic matter in biogenic vaterite.

A classical view on nonclassical nucleation

Understanding and controlling nucleation is important for many crystallization applications. Calcium carbonate (CaCO3) is often used as a model system to investigate nucleation mechanisms. Despite its great importance in geology, biology, and many industrial applications, CaCO3 nucleation is still a topic of intense discussion, with new pathways for its growth from ions in solution proposed in recent years. These new pathways include the so-called nonclassical nucleation mechanism via the assembly of thermodynamically stable prenucleation clusters, as well as the formation of a dense liquid precursor phase via liquid-liquid phase separation. Here, we present results from a combined experimental and computational investigation on the precipitation of CaCO3 in dilute aqueous solutions. We propose that a dense liquid phase (containing 4-7 H2O per CaCO3 unit) forms in supersaturated solutions through the association of ions and ion pairs without significant participation of larger ion clusters. This liquid acts as the precursor for the formation of solid CaCO3 in the form of vaterite, which grows via a net transfer of ions from solution according to z Ca2+ + z CO32- → z CaCO3 The results show that all steps in this process can be explained according to classical concepts of crystal nucleation and growth, and that long-standing physical concepts of nucleation can describe multistep, multiphase growth mechanisms.

SYNTHESIS OF CALCIUM CARBONATE NANOPARTICLES IN PRESENCE OF HYDROXYETHILIDEN DIPHOSPHONIC ACID

Particles of calcium carbonate were synthesized in the presence of additive of hydroxyethylidene diphosphonic acid (HEDP). This agent can form chelate complexes with calcium ions is solution or be adsorbed on the surface of calcium carbonate. The scale deposit was investigated by sedimentation, diffractometry and scanning electron microscopy. It was shown that the concentration of additive determines a mean size of the particles: the HEDP addition was found to reduce quite markedly the mean size of the particles (from 10 – 20 mm at HEDP concentration in the range of 0 – 10-5 mol/L to 10 nm at 10-2 mol/L). Moreover, the presence of HEDP in solution not only reduced the particles size but also modified their crystallographic structure: at low HEDP concentration calcite was the stable form, at 10-2 mol dm-3 HEDP stabilized the vaterite form of calcium carbonate. Measurements both of contact angles of HEDP solutions (in the heptane environment) at calcite single crystal and interfacial tension at heptane – HEDP solution interface showed the negligible change in the energy of calcite – HEDP solution interface. So, the formation of the carbonate nanocrystals at higher HEDP concentration may be ascribed to adsorption-induced decrease in crystals growth rate rather than to enhanced nucleation.Forcitation:Simonov Ya.I., Sokolov S.A., Skvortsova Z.N., Traskin V.Yu. Synthesis of calcium carbonate nanoparticles in presence of hydroxyethiliden diphosphonic acid. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 8. P. 96-99.

A Review of the Structures of Vaterite: The Impossible, the Possible, and the Likely

The importance of the metastable vaterite form of CaCO3 is increasingly appreciated as an intermediate between amorphous calcium carbonate and more stable crystalline polymorphs in biogenic calcification pathways. Thus, there is a need to be able to identify nanocrystals of vaterite unambiguously, despite uncertainties about its exact crystal structure. The structures that have been proposed for vaterite are all based upon a common average structure with orientationally disordered carbonate groups. However, there is much ambiguity in the literature about the actual superstructure, and hence diffraction behavior of vaterite, some misinterpretation of data, and some claims that cannot be correct. This critical review of the literature aims to resolve the issue. The orientationally disordered (2H) structure is unlikely to occur, and the most plausible structures all share a √3 × √3 superstructure in the xy plane. Most experimental evidence is consistent with occurrence of 2M and 6H polytypes, but ab initio m...

Pressure‐induced phase transitions of vaterite, a metastable phase of CaCO3

Pressure‐induced phase transitions of vaterite, a metastable phase of CaCO3, were observed from Raman spectra and X‐ray diffraction patterns at high pressure using diamond anvil cells at room temperature. Pressure dependence of Raman peaks assignable to the symmetric stretching vibration modes of carbonate ion indicated the phase transitions of vaterite. At 4.3 GPa, vaterite (vaterite I) transformed to a high‐pressure form of vaterite (vaterite II). With increasing pressure, a part of vaterite II gradually transformed to calcite III, and the remainder of vaterite II transformed to another new phase (vaterite III). The phase transition from vaterite II to calcite III was irreversible, and calcite III back‐transformed to calcite I during decompression. Moreover, at the pressures higher than 13.1 GPa, several diffraction spots were observed on an imaging plate, indicating another phase transition from vaterite III to a phase having coarse grains (vaterite IV). Our results indicate that vaterite undergoes more complex phase transitions at high pressure than other polymorphs of calcium carbonate, calcite, and aragonite. These phase transitions of vaterite will open a window to understanding phase transitions of metastable minerals at high pressure. Copyright © 2017 John Wiley & Sons, Ltd.

Sonosynthesis of Vaterite-Type Calcium Carbonate

Metastable nanoparticles of vaterite were formed using a simple ultrasound technique. The effects of ultrasound amplitude and duration, as well as solution concentration, were investigated. The produced particles were characterized using standard X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning and transmission electron microscopies (SEM and TEM, respectively). As expected, the ultrasound synthesis process caused the particle size to be smaller than with conventional (magnetic bar) stirring, and allowed for the reaction time to be shortened as the crystallization rate was increased. As shown by XRD, FTIR, and SEM, the ultrasound process also led to the formation of pure vaterite, though the presence of calcite occurred as the ultrasound power was reduced and the pulse time increased. For both conventional and ultrasound techniques, the particle size was reduced with an increase in starting solution concentration. Using this technique allows for reproducible, tailored c...

Synthesis of peanut-like calcium carbonate intermediates in silica system containing partially hydrolyzed polyacrylamide and heavy alkyl-benzene sulfonate

Calcium carbonate (CaCO3) crystals with various morphologies and polymorphs were synthesized from the aging calcium chloride (CaCl2) and sodium carbonate (Na2CO3) solution using inorganic silica as well as organic partially hydrolyzed polyacrylamide (HPAM) and surfactant heavy alkyl-benzene sulfonate (HABS) as effective crystal growth modifiers by the rapidly mixing method at 45°C. The effect of different additives on controlling calcium carbonate morphology has been investigated by field emission scanning electron microscopy (FESEM), fourier transform infrared (FT-IR) spectrometer and X-ray diffraction (XRD). Peanut-like CaCO3 particles were successfully obtained after the mixture system being aged for 6h at pH of 11.3±0.2, and the transition from sphere through peanut-like shape to cubic shape for CaCO3 particles occurred with increasing of aging time. All the CaCO3 particles were pure calcite when pH was unadjusted (pH=11.2±0.1), however, lower pH favored the formation of vaterite. The research results showed that the adsorption of HPAM and HABS on SiO2-coated CaCO3 surfaces played a crucial role in modifying the crystals morphologies. A hypothetical mechanism for the formation process of the peanut-like CaCO3 was presented.

Synthesis of calcium carbonate in trace water environments.

Calcium carbonate (CaCO3) was synthesized from diverse water-free alcohol solutions, resulting in the formation of vaterite and calcite precipitates, or stable particle suspensions, with the dimensions and morphologies depending upon the conditions used. The obtained results shed light on the importance of solvation during crystallization of CaCO3 and open a novel synthetic route for its precipitation in organic solvents.

Rapid growth causes abnormal vaterite formation in farmed fish otoliths.

Sagittal otoliths are essential components of the sensory organs that enable all teleost fish to hear and maintain balance, and are primarily composed of calcium carbonate. A deformity, where aragonite (the normal crystal form) is replaced with vaterite, was first noted over 50 years ago but its underlying cause is unresolved. We evaluated the prevalence of vateritic otoliths from two captive rearing studies which suggested that fast growth, due to environmental rather than genetic control, led to vaterite development. We then tested this by varying light and temperature to create phenotypes with different growth rates, which resulted in fast growers (5times larger) having 3times more vaterite than slow growers. A decrease in either the ratio of otolith matrix proteins (otolin-1/OMM-64) or [Ca2+]/[CO32-] may explain why fast growth causes vaterite deposition. As vaterite decreases hearing sensitivity, reducing growth rates in hatcheries may improve the welfare of farmed fish and increase the success of conservation efforts.

Synthesis of Unstable Vaterite Polymorph of Porous Calcium Carbonate Nanoparticles, Encapsulation of Anticancer Drug Cisplatin, Studying Release Kinetics for Safe, Targeted Delivery and Slow Release

Cisplatin is a commonly used anticancer drug which is the first generation of platinum-based anticancer drugs developed. The cis configuration enables the binding of the coordination complex to one or two DNA strand (s) and thereby crosslinking the DNA strands triggering the cells to die in a programmed manner. It is used to treat various types of cancers such as small cell lung cancer, ovarian cancer, bladder cancer, cervical cancer, and germ cell tumours. When administered into blood, cisplatin reacts with thiol containing proteins present in blood plasma thus reducing its bioavailability, increasing cytotoxicity and it is associated with numerous side effects including nephrotoxicity, neurotoxicity, nausea, vomiting and ototoxicity. In order to increase the bioavailability and to reduce dosage and cytotoxic effects to healthy cells thermodynamically unstable vaterite form of Porous Calcium Carbonate Nanoparticles are synthesized using the soft molecular template approach to synthesize them from aqueous solution. Hydrogen bonded networks of ethylene glycol and water are formed by mixing appropriate quantities of the two liquids to have spherical templates. Cisplatin is encapsulated in porous nanoparticles of the vaterite form of CaCO3 and studied the release kinetics of the drug in the solutions at different pH values. It is found that the drug is released slowly and steadily in the pH values of cancerous cells (pH range 5.0–6.0) but not in the pH ranges exhibited by healthy cells (pH range 7.0-8.0). Here, the synthesis and stabilization of nanoparticles of vaterite as well as their characterization, encapsulation of cisplatin and the slow minimum amount of constant release kinetics of the drug at various pH values are described. This is a way forward for safe and convenient chemotherapeutic route to various cancers. Graphical Abstract

Study of the Interaction of Eu3+ with Microbiologically Induced Calcium Carbonate Precipitates using TRLFS.

The microbial induced biomineralization of calcium carbonate using the ureolytic bacterium Sporosarcina pasteurii in the presence of trivalent europium, a substitute for trivalent actinides, was investigated by time-resolved laser-induced fluorescence spectroscopy (TRLFS) and a variety of physicochemical techniques. Results showed that the bacterial-driven hydrolysis of urea provides favorable conditions for CaCO3 precipitation and Eu3+ uptake due to subsequent increases in NH4+ and pH in the local environment. Precipitate morphologies were characteristic of biogenically formed CaCO3 and consistent with the respective mineral phase compositions. The formation of vaterite with some calcite was observed after 1 day, calcite with some vaterite after 1 week, and pure calcite after 2 weeks. The presence of organic material associated with the mineral was also identified and quantified. TRLFS was used to track the interaction and speciation of Eu3+ as a molecular probe with the mineral as a function of time. Initially, Eu3+ is incorporated into the vaterite phase, while during CaCO3 phase transformation Eu3+ speciation changes resulting in several species incorporated in the calcite phase either substituting at the Ca2+ site or in a previously unidentified, low-symmetry site. Comparison of the biogenic precipitates to an abiotic sample shows mineral origin can affect Eu3+ speciation within the mineral.

Physical properties and carbon dioxide capture of synthetic gamma-C2S cement composites in the early days of curing

This study investigates how the porosity and compressive strength of ordinary Portland cement (OPC) blended with different ratios of synthetic gamma dicalcium silicate (γ-C2S) change in the first 28 d of curing. The composites are cured either under normal atmospheric conditions (standard curing) or in a carbon dioxide chamber (accelerated carbonation curing). The carbon dioxide capture experiments are performed under constant conditions (10% carbon dioxide, 20°C and 60% relative humidity) and results are evaluated on days 3, 7 and 28, representative of the early curing days for the blends. The results show that the samples cured under carbonation exhibit higher compressive strengths after 28 d of curing than their corresponding samples cured under standard conditions. The results also show that the porosity of the 20 wt% γ-C2S/OPC blend cured under carbonation conditions is reduced from 29·0% to 19·4%, indicating the densification of the final product. This decrease in porosity is attributed to the formation of calcite and vaterite (μ-CaCO3) phases, by the free calcium oxide inside the pore structure reacting with carbon dioxide. These findings confirm that a 20 wt% γ-C2S/OPC blend cured under carbon dioxide undergoes densification, and this contributes to the enhanced durability and strength of carbon dioxide-cured cement products.

Micrographical, minerological and nano-mechanical characterisation of microbial carbonates from urease and carbonic anhydrase producing bacteria

Microbial carbonates are emerging as sustainable alternative cementing materials. We explore carbonate mineralisation by three bacterial isolates: Sporosarcina pasteurii, Bacillus pumilis and Bacillus megaterium that produce two enzymes urease and carbonic anhydrase. In vitro CaCO3 precipitation by bacterial isolates under three different energy sources: urea, NaHCO3 and CO2 was monitored quantitatively and qualitatively. Cell viability in different treatments was studied through fluorescent microscopy. Morphological and chemical constituents of the crystals formed by different bacterial isolates were analysed by scanning electron microscopy, X-ray diffraction and Energy dispersive X-ray spectrum. In a first attempt we estimate the mechanical properties of microbial products through nanoindentation and correlate them with the established techniques such as SEM and XRD. The biochemical processes produced a mixture of two forms of carbonate, calcite and vaterite, in different proportions. We demonstrate that it is possible to engineer the mechanical properties of the carbonates by controlling the biochemical processes.

Influence of acid-soluble proteins from bivalve Siliqua radiata ligaments on calcium carbonate crystal growth

In vitro biomimetic synthesis of calcium carbonate (CaCO3) in the presence of shell proteins is a heavily researched topic in biomineralization. However, little is known regarding the function of bivalve ligament proteins in the growth of CaCO3 crystals. In this study, using fibrous protein K58 from Siliqua radiata ligaments or coverslips as substrates, we report the results of our study of CaCO3 precipitation in the presence or absence of acid-soluble proteins (ASP) from inner ligament layers. ASP can disturb the controlling function of K58 or a coverslip on the crystalline phase, resulting in the formation of aragonite, calcite, and vaterite. In addition, we identified the following four primary components from ASP by mass spectroscopy: alkaline phosphatase (ALP), ABC transporter, keratin type II cytoskeletal 1 (KRT 1), and phosphate ABC transporter, phosphate-binding protein (PstS). Further analysis revealed that the first three proteins and especially ALP, which is important in bone mineralisation, could affect the polymorphism and morphology of CaCO3 crystals by trapping calcium ions in their domains. Our results indicate that ALP may play an important role in the formation of aragonite in S. radiata ligaments. This paper may facilitate our understanding of the biomineralization process.

Kinetics and Mechanism of Calcium Hydroxide Conversion into Calcium Alkoxides: Implications in Heritage Conservation Using Nanolimes.

Nanolimes are alcohol dispersions of Ca(OH)2 nanoparticles used in the conservation of cultural heritage. Although it was believed that Ca(OH)2 particles were inert when dispersed in short-chain alcohols, it has been recently shown that they can undergo transformation into calcium alkoxides. Little is known, however, about the mechanism and kinetics of such a phase transformation as well as its effect on the performance of nanolimes. Here we show that Ca(OH)2 particles formed after lime slaking react with ethanol and isopropanol and partially transform (fractional conversion, α up to 0.08) into calcium ethoxide and isopropoxide, respectively. The transformation shows Arrhenius behavior, with apparent activation energy Ea of 29 ± 4 and 37 ± 6 kJ mol(-1) for Ca-ethoxide and Ca-isopropoxide conversion, respectively. High resolution transmission electron microscopy analyses of reactant and product phases show that the alkoxides replace the crystalline structure of Ca(OH)2 along specific [hkl] directions, preserving the external hexagonal (platelike) morphology of the parent phase. Textural and kinetic results reveal that this pseudomorphic replacement involves a 3D diffusion-controlled deceleratory advancement of the reaction front. The results are consistent with an interface-coupled dissolution-precipitation replacement mechanism. Analysis of the carbonation of Ca(OH)2 particles with different degree of conversion into Ca-ethoxide (α up to 0.08) and Ca-isopropoxide (α up to 0.04) exposed to air (20 °C, 80% relative humidity) reveals that Ca-alkoxides significantly reduce the rate of transformation into cementing CaCO3 and induce the formation of metastable vaterite, as opposed to stable calcite which forms in untransformed Ca(OH)2 samples. Similar effects are obtained when a commercial nanolime partially transformed into Ca-ethoxide is subjected to carbonation. Such effects may hamper/delay the strengthening or consolidation effects of nanolimes, thus having important implications in the conservation of cultural heritage.