Crystal Form Of Calcium Carbonate Research Articles

Aragonite and Its Composites: Preparations, Properties and Applications

AbstractAragonite, a metastable crystal form of calcium carbonate, exhibits the highest density and hardness among all species. Diversified forms of aragonite composites can be produced through different preparation processes, forming a relatively complete system in various application fields. Their properties and applications are determined by their multiple levels of structures and shapes. However, research information for aragonite‐related fields is currently lacking integration and clarification. This review provides a comprehensive overview on the preparation methods, properties, and potential applications of three main aragonite‐based materials: aragonite particles, nacre‐inspired mineralized aragonite composites (NMACs), and shell‐derived aragonite nanoparticles (SANPs). The formation mechanisms and versatile applications of these materials are thoroughly surveyed based on their initial precursor, reaction conditions, product forms including filler of aragonite whiskers synthesized by carbonation reaction; functional materials of NMACs fabricated by amorphous calcium carbonate‐organic matter (ACC‐OM) mediated process; biomedical materials of SANPs derived from aragonite cockle shells. Overall, this review aims to provide assistance for customized production of aragonite‐based materials as well as new research directions for both pure aragonites and its composites.

Strength characteristics of biomimetic carbonate precipitation (BCP) treated mortar under cyclic loading

L-Aspartic acid (L-Asp) has the potential to mediate the crystal form of calcium carbonate, and biomimetic carbonate precipitation (BCP) with L-Asp as the crystal modifier has been proposed for green mortar. However, the cyclic properties of BCP-treated mortar are rarely studied. In this study, the direct shear test was first performed to prove the ability of BCP treatment in improving the shear strength, friction angle, and cohesion of sand. It shows that higher normal stress can promote the pre-peak shear shrinkage of the specimen, while inhibiting the development of post-peak shear dilation. Then, the pre-peak cyclic shear test was conducted under different normal stresses, and the cyclic response of BCP-treated mortar with different number of loading cycles was investigated. The phenomenon of shear softening was observed, and the stress-strain behavior of the specimen was further studied. Finally, the specimens after cyclic loading were prepared for the direct shear test again to examine their post-cyclic properties. Results show that the specimen with more loading cycles has lower post-cyclic shear strength, while high normal stress can alleviate the decrease in shear strength after cyclic loading. With the increase in cyclic numbers, the cohesion of the specimen decreases, but the friction angle varies slightly. This study is expected to provide a deeper understanding on the shear response of BCP-treated mortar with cyclic loading.

Enhancement mechanism of different recycled fine aggregates by microbial induced carbonate precipitation

The high water absorption and low strength of recycled fine aggregates limit its resource utilization in building materials. Microbial induced calcium carbonate precipitation (MICP) is an environmentally friendly method to improve recycled fine aggregates. However, the precipitation efficiency of MICP is also affected by the characteristics of various recycled fine aggregates, such as pH environment and pore structure. In this study, the effects of MICP on the properties of three recycled fine aggregates were studied, and enhancement mechanism was analyzed. The results show that the performance of biological calcium carbonate can effectively improve the performance of recycled aggregates. A large amount of calcium carbonate formed on the surface and some calcium carbonate formed in pores larger than 0.2 μm inside are the keys to enhance the performance of recycled aggregates. The modification effect on RBA was the best, that on RCA was next, while that on RMA was the worst. The crystal forms of calcium carbonate were different due to the pH environment in various recycled aggregates. A low pH environment is beneficial for the formation of Vaterite calcium carbonate, while high pH favors rhombic calcite.

Systematic optimization of a novel, cost-effective fermentation medium of Sporosarcina pasteurii for microbially induced calcite precipitation (MICP)

• The fermentation medium and conditions of Sporosarcina pasteurii are optimised. • A cheap nitrogen source, corn-steep liquor, replaces soybean peptone in the medium. • The medium cost was reduced by 50.5%, and the urease activity was increased by 24.2%. • The unconfined compressive strength of MICP-treated samples was increased by 21.3%. • XRD diagram shows that calcite was formed in the MICP-treated samples. Microbially induced calcite precipitation (MICP) is a promising technology for sand fixation, ground stabilisation, concrete crack repairment, and contaminated soil remediation. Sporosarcina pasteurii is the most used urease-producing bacterium for MICP applications. This study proposes a novel, cost-effective culture medium for S. pasteurii using corn-steep liquor as a cheaper nitrogen source, partially replacing the soybean peptone, decreasing the medium cost by 50.5 %. The optimal fermentation conditions were determined by single-factor experiments at a temperature of 30℃, an initial pH of 8.0, and an inoculation amount of 0.5 %. The optimal medium composition was determined by orthogonal experiments at 15 g/L soybean peptone, 30 g/L corn-steep liquor, 10 g/L urea, and 3 g/L sodium dihydrogen phosphate. As a carbon source, lactose was found to inhibit urease activity and should not be added. The novel medium increased the urease activity by 24.2 % and enhanced the unconfined compressive strength (UCS) of the MICP-treated sample to 2.39 MPa, which increased by 21.3 %. XRD analysis shows that calcite, the most stable crystal form of calcium carbonate, was formed in the samples. ESEM images show more calcium carbonate generated on the sample surface, and the cementation between sand particles was better. Therefore, this novel, cost-effective medium made the Sporosarcina pasteurii show satisfying MICP performance and alleviated economic concerns about the large-scale application of MICP.

Mechanical and Engineering Behavior of MICP-Treated Coarse Siliceous Sands

Microbial-induced calcium carbonate precipitation (MICP) technology has been widely used in geotechnical engineering. The undrained and unconsolidated (UU) triaxial tests were conducted in this study to investigate the effect of bio-cementation concentration and treatment times on the mechanical behavior of MICP treated siliceous sands. Test results indicated that the strength of treated specimen is significantly affected by the bio-cementation concentration. The normalized σ′p/σ′p_u increases exponentially with treatment times and produced calcium carbonate. For the same treatment times, the higher the bio-cementation concentration, the larger the produced calcium carbonate and smaller corresponding failure strain. The void ratio and permeability of treated specimens decrease lineally with treatment times increase. The higher the used bio-cementation concentration, the larger the reduction of void ratio and permeability. SEM analysis illustrates that when the bio-cementation concentration is 0.5 mol/L, the crystal form of calcium carbonate is mainly spherical, while the concentrations are 0.7 mol/L and 1.0 mol/L, the crystal form of calcium carbonate is mainly block. This can explain from the perspective that the treatment effect of 0.7 mol/L and 1.0 mol/L bio-cement cementation is better than that of 0.5 mol/L.

The preparation of calcium carbonate with different morphologies under the effect of alkanolamide 6502

The shape, size and polymorph of the crystals will affect their separation, drying and other properties. Surfactants may affect the crystallization process and crystalline products’ properties by changing the surface tension in the solution. In this paper, the effects of alkanolamide 6502 as additive on the morphology of calcium carbonate was studied under the conditions of different additive volumes, temperatures and stirring rates. The results showed that the presence of alkanolamide 6502 has a certain effect on the morphology and crystal form of calcium carbonate. The addition of alkanolamide 6502 during the crystallization process was conductive to form vaterite, and the particle size of calcium carbonate was more uniform. Meanwhile, alkanolamide 6502 can change the surface properties of the product from hydrophilic to hydrophobic, preventing the agglomeration. Moreover, vaterite is more likely to form in the presence of alkanolamide 6502, and it is explained from the perspective that adsorption of hydroxyl on the crystal surface changes the physical surface properties of the crystal and inhibits the transformation of polymorphs.

Effect of H2S on the corrosion-fouling behaviors of Cu-base surface

Based on the First-principles method of density functional theory (DFT), the adsorption of H2S on the primary growth surface (001)(111)(110) of Cu-base was investigated. The results demonstrate that the stable adsorption position of H2S on Cu(001)(111)(110) surface is t-parallel, b-H-down-c and h-H-down-c, respectively. And the corresponding adsorption energy is the minimum of −0.580 eV, −0.560 eV, −0.527 eV. After doping Zn in Cu, b-parallel, b-parallel and h-H-down-p are the stable adsorption position of H2S on Cu–Zn(001)(111)(110) surface. More chemical bonds form on adsorption sites of Cu and Cu–Zn substrate. Crystal structure of Cu doping Zn becomes unstable and easy to be corroded. Additionally, the experimental results reveals that copper shows better corrosion resistance of H2S than that of brass. Trends of fouling deposit curve of copper and brass are similar while the fouling is prone to deposit on the surface of brass after H2S corrosion. The consequences evidence that the fouling deposition can be influenced by the corrosive surface of materials and the fouling is prone to deposit on the corrosive pits and cracks. Furthermore, the crystal form of calcium carbonate on the surface of brass and copper after H2S corrosion is primarily aragonite and calcite. The corrosion products can promote the fouling adhesion.

Comparison of proinflammatory potential of needle-shaped materials: aragonite and potassium titanate whisker

Among the crystal forms of calcium carbonate, aragonite has needle-like shape. Although materials with needle-shaped crystals are associated with pulmonary toxicity, the toxic activity of aragonite is unclear. Therefore, proinflammatory potential of aragonite, neutralized aragonite and potassium titanate whisker was evaluated. The cellular effects of aragonite were weaker than those of potassium titanate whisker. Aragonite treatment induced the expression of chemokines in A549 cells and macrophages. Although aragonite exhibited proinflammatory effects in vitro, pulmonary inflammation was not observed in vivo after intratracheal administration of aragonite in mice. We did not observe the induction of inflammatory cytokine secretion or tissue lesion in the lungs of mice after administration of aragonite. Potassium titanate whisker treatment induced chemokine secretion in vitro. An increase in the number of neutrophils was observed in the mice lung tissue after administration of potassium titanate whisker. Aragonite and neutralized aragonite both induced an increase in the levels of intracellular calcium, but the levels were significantly higher in cells treated with aragonite than in cells treated with neutralized aragonite. These results suggested that intracellular calcium release mediates the cellular effects of aragonite. The toxicity of aragonite based on its needle-like structure was also not observed.

XRD and 29Si MAS NMR study on carbonated cement paste under accelerated carbonation using different concentration of CO2

In this study, the chemical composition of cement pastes, exposed to accelerated carbonation using different concentration of CO2 (3%, 10%, 20%, 50%,100%), have been determined and compared with those of natural carbonation (0.03%). Quantitative X-ray diffraction (QXRD) and 29Si Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) were used for characterisation and quantitative analysis of the carbonated phases. The obtained QXRD results revealed that the complete carbonation was hardly attained. Calcite, aragonite and vaterite were in co-existence after accelerated carbonation, while vaterite was dominant. The preferential polymorphic precipitation of the three crystal forms of calcium carbonate was affected by the carbonation degree of C-S-H and the duration of the carbonation process, but not by the concentration of CO2. The NMR results indicated that C-S-H gel was strongly decalcified, and calcium modified silica gel was formed after carbonation. The C-S-H decalcification, under all the accelerated carbonation conditions, was clearly more pronounced than that under the natural carbonation conditions. When the concentration of CO2 was in the range of 3%–20%, the ratio of decalcified to remaining C-S-H was similar, in a range of 5–6, while under the higher concentration of CO2 this ratio was increased to >8. Therefore, in consideration of both acceleration rate and measurement uncertainty, the higher concentration, up to 20%, of CO2 in an accelerated carbonation should be applicable.

Using Cuttlebone Powder to Produce Green Concrete

Abstract Limestone has been commonly used in concrete for several decades. Moreover, calcium carbonate was used as a portion of cement content. Therefore cuttlebone powder, which is composed of a naturally occurring crystal form of calcium carbonate named aragonite, was used in concrete as a substitution of a portion of cement content in this research program for the first time. It led to the production of green concrete which is a type of concrete causes less harm to environment. 3, 5 and 7 percent of cement were substituted with cuttlebone powder. For this purpose, 4 concrete mix designs included 36 cubes, 4 cylinders and 4 prisms were casted. Results showed that weight of the specimens with cuttlebone powder was lower than control specimen. Moreover, by adding cuttlebone powder to concrete, slump increased. Although compressive and tensile strengths of the specimens with cuttlebone powder were lower than control specimen, but the specimen with 3% cuttlebone powder had adequate strength. Besides, three-point flexural strength of the concrete with 3% cuttlebone powder was higher than control specimen. It seems that by reducing water content of the specimen with cuttlebone powder to have similar slump to the control specimen, better performance of concrete can be achieved. So, this natural material can be used instead of a portion of cement to produce green concrete.

Effect of Mixing Patterns for Bio-Cement

This research studied the effect of mixing patterns for the bio-cement in the pilot test. The bio-cementation process initiated the crystal forms of calcium carbonate (CaCO3) to bind soil particles. Formation of CaCO3 was useful for the stabilization of earth structures. Soil samples were mixed with the solution containing 250mM of CO(NH2)2, 250mM of Ca2+ (by CaCl2), and urease concentrations of 20 % (v/v). For clay, there were three types of mixing blades; the rectangle, the spiral and the comb blades. The research found that firstly the sample mixed by the comb blade showed the highest value of shear wave velocity of 210.5 m/s. Secondly, the sample mixed by the rectangle blade showed the shear wave velocity of 167.3 m/s. Lastly, the sample mixed by the spiral blade showed the lowest value of the shear wave velocity of 150.6 m/s. For sand, there were 4 injection methods; (a) pour all the solution at one time (b) continuous drop (c) period drop and (d) period injection. The research found that the method (a) was a disadvantage method since it improved the ground only at the bottom area. In the same way, the method (b) was also a disadvantaged method because it improved the ground only at the top area. The most recommended methods were the methods (c) and (d) which improved the ground strength continuously along the depth.

Effect of Urease Dosages in Biocementation Process for Improving Strength of Sandy Soil

Soil biocementation is the new technique using biochemical process to initiate the crystal forms of calcium carbonate (CaCO3) to bind the soil particles resulting in soil mechanical improvement. This research examines the effect of urease (UR) dosages on the strength development of sandy soil in biocemented sand reactor (BSR). Our results found that urease dosages between 5-30% (v/v) affected the strength development in sandy soil in term of shear modulus (G). Addition of UR resulted on an increase of solution pH. Highest solution pH during the treatment was found at UR 20%, as well as highest G value. Formation of CaCO3 in biocemented sand could be useful for the stabilization of the sand or earth structures.

The unique reflection spectra and IR characteristics of golden-color seawater cultured pearl

A comparative study on the natural-color golden seawater cultured pearls and the treated-color golden seawater cultured pearls were carried out by UV-Vis reflectance spectra. Furthermore, the frequency variations of v3, v1 , v2 and v4 bands of the aragonites (a crystal form of calcium carbonate) with the positions of nacreous layer and nucleus in natural or treated-color golden-color seawater cultured pearls were firstly systematically measured. The results showed that: (1) based on the results of UV-Vis reflectance spectra of natural or treated-color golden seawater cultured pearls, interestingly, it was firstly found that the natural-color golden one displays slight varied UV-Vis reflection spectra because of its different surface microstructure located on the outer nacreous layer. Meanwhile, according to the characteristic of UV-Vis reflectance spectra of treated-color golden ones, the treated-color ones were firstly classified to four categories. (2) The frequency of v2 band of aragonite in nacreous layer of natural-color or treated-color golden pearls was greater than the other one from theirs corresponding nucleus, namely A clear blue shift was observed in the former. But the other bands were not altered in the positions of nacreous layer and nucleus, and had the same valves with synthetic aragonites. Additionally, the location of absorption bands of aragonite in nacreous layer of natural or treated-color golden pearls had no frequency shift, which indicates that the behavior of color-treating had no effect on the crystal structure of golden pearls.

Calcium carbonate deposition on layer-by-layer systems assembled from star polymers

Layer-by-layer (LbL) systems constructed via electrostatic attraction or other forces can be used as templates in biomimetic mineralization. In this work, 21-arm star poly(acrylic acid) (star-PAA) and 21-arm star poly[2-(dimethylamino)ethyl methacrylate] (star-PDMAEMA) were successfully synthesized from a cyclodextrin core via atom transfer radical polymerization (ATRP). The star polymers were used to construct three kinds of LbL systems: negatively charged star-PAA with positively charged chitosan (CHI) as a model of unconfined space for mineralization, and positively charged star-PDMAEMA with negatively charged poly(styrene sulfonic acid) sodium salt (PSS), which had acid-etched holes or constructed within a porous polycarbonate filters, as two different models of confined space for mineralization. Different crystal forms of calcium carbonate were obtained using the three systems, so these LbL systems assembled from star polymers could be new tools for developing functional materials and investigating fundamental aspects of the mineralization process.

Occurrence of a cold-water coral along natural pH gradients (Patagonia, Chile)

Increasing dissolution of anthropogenic-released carbon dioxide into the world’s oceans is causing ocean acidification (OA). OA is thought to negatively affect most marine-calcifying organisms, notably cold-water corals (CWC), which may be especially sensitive due to the deep and cold waters they normally thrive in. However, the impact of OA on CWC is difficult to predict. Recorded distributions of CWC are rarely linked to in situ water chemistry, and the boundaries of their distributions are not clearly defined. The fjord Comau in Chilean Patagonia features pronounced pH gradients, and up to 0.5 pH units have been recorded both vertically (at some sites within 50 m depth) and less distinct horizontally (from head to mouth). The cosmopolite coral Desmophyllum dianthus grows along the course of the fjord and of the entire pH range. It occurs in shallow depths (below 12 m, pH 8.1) as part of a deep-water emergence community, but also in 225 m depth at a pH of 7.4. Based on pH and total alkalinity, data calculations of the associated carbonate chemistry revealed that this CWC thrives commonly close the aragonite (the orthogonal crystal form of calcium carbonate, the mineral structure of coral skeletons) saturation horizon and even below. This suggests a high adaptation potential of D. dianthus to adjust its calcification performance to conditions thermodynamically unfavourable for the precipitation of aragonite.

Study on scale inhibition performances and interaction mechanism of modified collagen

The modified collagens with rich carboxyls were prepared by chemically modifying collagen, which was firstly extracted by hydrolyzing chrome shavings, using the multi-aldehyde acid compounds (MACs) as the modifiers. Then those modified collagens and the blank collagen were used as scale inhibitors to implement scale inhibition tests. Scanning electron microscope (SEM) and XRD analyses were utilized to characterize morphology and crystal form of calcium carbonate scale. Results showed that the Ca2+ concentration and pH were the main influencing factors within the scale inhibition system, specifically the scale inhibition efficiency would be reduced with the increase of Ca2+ concentration and pH. Both the two types of scale inhibitors were more sensitive to the temperature, i.e., the scale inhibition rates were in a downward trend with augment of the temperature. The crystal form of calcium carbonate could be completely distorted to form a vaterite crystal through the action of modified collagens, thus the scale inhibition effect is achieved.

Effects of Temperature on the Crystallization of Calcium Carbonate in Egg White Protein Solution System

Various crystal forms of calcium carbonate were successfully synthesized with CaCl2 and Na2CO3 in 10%(V/V) egg white protein solution system at 20 °C, 40 °C and 60 °C, respectively. The obtained calcium carbonate were characterized by SEM, XRD, FTIR and TG. In addition, the possible mechanism of crystal formation were analyzed. The results indicated that egg white protein could regulate the crystal forms of calcium carbonate and the calcium carbonate, which contained a small amount of egg white protein and consisted of mixed calcite and aragonite, was mainly spherical. With the temperature rosing, the vaterite content gradually increased while the calcite decreased.

Preparation of vaterite type calcium carbonate by using ultrasound and application to ink-jet paper

Calcium carbonate is used widely in various industries because it is costless and harmless. Vaterite is one type of crystal form of calcium carbonate and occurs rarely in nature. This study aims at safe synthesis method to prepare vaterite and its application to ink-jet paper. A new method for preparing pure vaterite has been established by using ultrasonic homogenizer to mix and agitate K2CO3 and CaCl2 solutions. Shapes and sizes of vaterite particles formed are controllable by selecting a surfactant present in the mixing solution. Vaterite type calcium carbonate is easily transformed into calcite type in water. However, high pH, addition of surfactant SDBS (Sodium Dodecyl Benzene Sulfonate) and immersion in ethanol lowered or prevented crystal transformation because of low solubility constants. Ink-jet printing test was performed with vaterite-coated paper and resulted in high print quality. Bleeding problem did not occur as well as commercial silica coated ink-jet paper, although calcite coated and trial silica coated papers exhibited worse bleeding probably because high hydrophilicity of vaterite promoted quick absorption of inks inward before spreading laterally on the surface.

Control over nanocrystalization in turbulent flow in the presence of magnetic fields

The influence of the magnetic field and the water flow on the crystal form of calcium carbonate precipitated from low-concentration water solution was followed systematically. By changing the strength of the field, the calcite/aragonite/vaterite ratio varied. The crystal form and the particle size distribution of the precipitated calcium carbonate were determined by using X-ray analyses and transmission electron microscopy (TEM). A simple hydrodynamical model, using the Navier–Stoke's and Maxwell's equations, predicts that there is a strong energy coupling and transfer between turbulent flow and the magnetic fields, which can be amplified to high values. Since the formation of aragonite is enhanced in the presence of magnetic field, scaling is prevented in turbulent flow.

Nucleation and crystallization of CaCO 3 in applied magnetic fields

The formation of calcium carbonate is not only a common ionic reaction that takes place in natural processes, but also creates a problem known as scaling, which is present in our every day life and in various industrial processes and technologies. In spite of the simplicity of the reaction there is considerable variability in the properties of the solid product, such as: crystal form, particle size distribution, electro-kinetics potential, etc. The influence of the magnetic field on calcium carbonate precipitation has been known for a long time but despite a lot of effort, which has been made to explain this effect, researchers still disagree on the mechanism(s) responsible for it. The focus of our research work was to follow systematically the influence of the magnetic field on the crystal form of calcium carbonate precipitated from low concentration water solutions. By changing the strength of the field and the flow rate of the water through the system the calcite/aragonite/vaterite ratio varied. The crystal form and the particle-size distribution of the precipitated calcium carbonate were determined by using X-ray analyses and TEM. The theoretical part of the work was to study the mechanism of the influence of the magnetic field on the nucleation and further crystallization of calcium carbonate. Starting from ab initio calculations the fundamental physics knowledge was used to propose a mechanism for a better understanding of the phenomena.