Calcium Carbonate Crystal Growth Research Articles

Kinetic mechanisms of organophosphine compounds on calcium carbonate crystal growth: Cruising effect and Spatial matching

Calcium carbonate (CaCO3) is a common mineral in industrial water systems. Organophosphate is a widely used scale inhibitor with 100% inhibition of thousands of mg/L of calcium (Ca2+) ions at concentrations below 10 mg/L. However, chelating agent EDTA is hundreds of times more effective in achieving the same inhibitory effect. Our study explored the significant difference in CaCO3 growth inhibition by these compounds. Through experiments combining molecular dynamics simulations and quantum chemical calculations, we have found that organophosphines dynamically capture and release Ca2+ ions, enhancing the solubility of Ca2+ ions and impeding CaCO3 growth through a mechanism known as the “cruising effect”. Simultaneously, the lattice distortion induced by “spatial matching” was employed to inhibit the growth of CaCO3. On the other hand, chelating agents exhibited robust coordination forces, particularly with ligand atoms (O and N), showcasing superior chemometric characteristics. These findings illuminated the distinct mechanisms of CaCO3 growth inhibition.

New model for aspartic acid species in aqueous calcium carbonate growth environments: challenges and perspectives.

The lack of experimental data on the dynamics of aspartic acid species in water for its range of protonation states and the details of their atomic-level interaction with aqueous calcium carbonate species is a driver for accurate force field development. A classical model that is consistent with the few pieces of experimental data available and with first principles calculations has been developed. The complex dynamics of the aspartate anions relevant to biomineralization and calcium carbonate crystal growth has been explored in water, providing a quantitative description of solvation structure and free energies, including conformational free energy profiles and pairing free energies. The model has been used to probe the structure and dynamics of aqueous calcium aspartate homo- and hetero-chiral clusters, confirming their unlikelihood due to weak and water-mediated interactions. This supports the hypothesis that the formation of such clusters, observed while growing vaterite in the presence of acidic chiral amino acids, is favoured by the presence of the crystal surface.

Investigation on mechanical properties of biomimetic mineralized mortar incorporated with boric acid modifier

Microbially induced carbonate precipitation (MICP) has been intensively studied as a potential method to improve engineering properties of soil. However, MICP has limitations due to the introduction of microorganisms and the difficulty of controlling the calcium carbonate crystal precipitation model. This study proposed biomimetic mineralized mortar based on the biomimetic-chemically induced carbonate precipitation (BCICP) method with boric acid as a crystal modifier. Similar to the bacteria in MICP, boric acid can promote the nucleation of calcium carbonate and the adsorption of calcium carbonate on the surface of sand particles. Besides, the boric acid concentration can effectively change the precipitation mode of calcium carbonate. Unconfined compression strength (UCS) test and microscopic characterization were conducted to investigate the mechanism of boric acid modifying calcium carbonate crystal growth and precipitation morphology. The results show that with the increase of boric acid concentration, the reinforcement efficiency of calcium carbonate increased. With the increase of boric acid concentration, the crystalline calcium carbonate changed from a cube-shaped calcite with a smooth surface to a spherical calcite with a rough surface and the coating pattern of calcium carbonate distribution on the surface of sand particles was weakened, while the bonding-filling pattern was enhanced. Besides, the cementing fluid concentration can also affect the reinforcement efficiency of calcium carbonate and with the participation of boric acid, biomimetic mineralized mortar can use the high concentration cementing fluid to achieve effective strength enhancement. This study confirms that boric acid could effectively modify the form and distribution of calcium carbonate between sand particles, and enhance the cementation between calcium carbonate and sand particles.

Structural and functional analyses of chitinolytic enzymes in the nacreous layer of Pinctada fucata

In this study, chitinolytic activity was confirmed in the protein extracted from the inner nacreous layer of Pinctada fucata shells. Allosamidin, a specific inhibitor of family 18 chitinase, was injected into pearl oysters, and an abnormal organic membrane was observed in the nacreous layer. When shell-notched individuals were injected with allosamidin, the organic fibers in the regenerated site were thicker than those without allosamidin treatment. To identify chitinases in the nacreous layer, proteins extracted from the nacreous layer were analyzed using LC-MS/MS. Two chitinases (PfCN1 and PfCN2) were identified, and their different spatial expression patterns were observed in mantle tissue. To understand the function of chitinolytic enzymes in nacre formation, we designed an in vivo gene knockdown experiment using PfCN1 and PfCN2 dsRNA, and in vitro calcium carbonate crystallization experiments using chitinolytic enzymes. In the knockdown experiment, abnormal aragonite tablets and organic films were observed in the nacreous layer. In the crystallization experiment, we found that the thickness of the chitin film decreased and the space between the chitin fibers increased when calcium carbonate was formed on the chitin film on the glass substrate with chitin-degrading enzyme treatment. These reactions induce the growth of calcium carbonate crystals through the chitin film. The penetration of chitin film by calcium carbonate is similar to that of mineral bridges that connect the nacre tablets vertically. These results showed the novel function of chitinolytic enzymes that will give a comprehension of nacre formation.

Gel-mediated chemo-mechanical control of calcium carbonate crystal formation

The production of synthetic crystals with controlled shapes and properties is an enticing prospect, yet, the production of such materials is an ongoing challenge. Here, we present a strategy for chemo-mechanically directing the growth of crystals with non-equilibrium structures using a custom-designed double-diffusion cell. We combine chemical additives (e.g., Mg2+ ions) and mechanical confinement (e.g., hydrogel networks) to modulate the growth of calcium carbonate crystals. Specifically, the combination of Mg2+ ions with a strong agarose gel results in calcitic structures, at the gel-glass slide interface, with distinct fried egg-like morphologies and radial or Maltese-cross extinction patterns. In contrast, precipitation with only Mg2+ or agarose results in aragonite spherulites or squished calcite rhombohedra, respectively. Raman spectroscopy and energy dispersive spectroscopy of the “fried eggs” reveals that they are composed of Mg-calcite, which becomes less disordered over time, and the “egg whites” make this transition before the “yolks”. We propose that the “fried eggs” form due to a spherulitic growth process molded by the crystallization-induced delamination of the gel away from the glass slide at the gel-glass interface. In support of the importance of the gel-glass interface, the “fried eggs” do not form when the glass slide is treated with a hydrophobic silane, suppressing heterogeneous nucleation and weakening the interfacial adhesion between the gel and glass, making it easier for the gel to delaminate, thus reducing the confinement effect. As such, this work highlights the important chemo-mechanical role that gel environments can play in crystal formation.

Air nanobubbles retard calcite crystal growth

Demands for “green” additives that control the crystal growth and inhibit the scale formation in industrial processes are growing as never before. Nanobubbles can be the green additive for inhibiting and/or promoting the crystal growth of calcium carbonate, given their well-known unique physicochemical properties. This paper reports for the first time the changes in the crystal growth rate of calcite in liquid in the presence of air nanobubbles. We injected the air nanobubbles into the solution and studied the calcite crystal growth for the first 4 h in a static condition at 20 °C and 88 °C. We found that air nanobubbles retarded the growth rate of calcite crystal by up to 53 % and 33 % at 20 °C and 88 °C, respectively. The retardation of calcite crystal growth could differ with different number densities of air nanobubbles added to the solution. A higher number density of nanobubbles generally showed slightly greater retardation throughout the tested 4 h. Air nanobubbles may influence the crystal growth either by changing solid-liquid interfacial tension on the crystal surface, reducing the free growth sites, adsorbing Ca2+ ions, playing roles in bubble mattress and thermal buffering on the crystal surface, or combinations of them. Our findings suggest that air nanobubbles can be utilized as a green inhibitor of calcite crystal growth and calcium carbonate scale in broad industrial areas.

Controllable synthesis and characterization of high purity calcium carbonate whisker-like fibers by electrochemical cathodic reduction method

Although the electrochemical method has been certificated as a promising way for the synthesis of calcium carbonate whiskers, researches on the controllability and efficiency are ignored. In this work, the electrochemical synthesis of calcium carbonate whiskers was studied to evaluate its controllability and efficiency. Micrograph and X-ray diffraction analysis results indicated calcium carbonate whiskers was successfully synthesized with a high production of 94.59% by using electrochemical method to stimulate cathodic reaction in calcium-containing solution. Length and aspect ratio of whisker can be controlled by regulating nucleation and growth conditions. The optimal conditions for whiskers synthesis were nucleating 5 min at 18 V and growing 55 min at 2 V in the solution containing 600 mg/L of calcium chloride, 300 mg/L of sodium bicarbonate, and 150 mg/L of magnesium chloride with a constant temperature of 70 °C. The calcium carbonate whisker has an 18.78 μm whisker length and 36.82 aspect ratio. The product morphology depended on the uniformity of carbonate and the presence of magnesium. The uniform distribution of the generated CO 3 2− was responsible for producing CaCO 3 whiskers. Besides, presence of magnesium can avoid of hydroxide overproduction and regulate supersaturation of CaCO 3 during synthesis to control the one-dimensional growth of whiskers. This work demonstrated the potential of controllable and efficient synthesis of calcium carbonate whiskers using electrochemical method. • Synthesize calcium carbonate whiskers with aspect ratio of 36.82 on stainless-steel cathode. • Whiskers length and aspect ratio were controlled through regulating nucleation voltage and reaction temperature. • Whiskers morphology depended on the uniformity of carbonate and the presence of magnesium. • Colloidal precipitate of Mg(OH) 2 promoted the one-dimensional growth of calcium carbonate crystals.

On the mechanism of calcium carbonate polymorph selection via confinement.

Organisms deposit various biominerals in the course of their biomineralisation. The most abundant of these is calcium carbonate, which manifests itself in several polymorphs. While organisms possess the ability to control the specific polymorph deposited, the exact mechanism by which polymorph selection takes place is not yet fully understood. Because biominerals often grow within confined spaces, one of the suggested possibilities was that polymorph selection might be an outcome of confinement. Confining conditions have indeed been extensively shown to have a strong impact on the nucleation and crystal growth of calcium carbonate and, in particular, on its polymorph selection. However, despite numerous studies on the crystal growth of calcium carbonate in confined spaces, the mechanism of polymorph selection under confinement has not been elucidated. Herein, we discuss previously reported results and suggest a mechanistic explanation of the observed selective formation of calcite or aragonite or vaterite. We consider the possible effects of charged confining inner surfaces and of the sizes of the confining pores, and discuss whether the predominantly precipitating phase is amorphous calcium carbonate. We also discuss two possible scenarios of crystallization from amorphous calcium carbonate under conditions of confinement: via solid-state transformation or via a mechanism of dissolution-reprecipitation.

Melamine-formaldehyde microcapsules encapsulating HEDP for sustained scale inhibition

Adding scale inhibitors is an efficient and economical solution to the troublesome scale deposition in various industrial productions. However, the direct use of liquid scale inhibitors often fails to provide long-term effective control and will cause a large amount of waste of scale inhibitors. Encapsulating the scale inhibitor into microcapsules is an advisable new approach to solving this problem. In this work, a water-soluble scale inhibitor (1-hydroxy ethylidene-1,1-diphosphonic acid, HEDP) was encapsulated into melamine formaldehyde microcapsules for the first time by in-situ polymerization using inverse emulsion (W/O emulsion) as a template. The influence of synthesis parameters (water-to-oil ratio, the amount of HEDP, stirring speed) on the morphology and particle size was investigated, and microcapsules with smooth surface, regular spherical shape and good dispersibility were obtained. The microcapsules possessed encapsulation efficiency exceeding 80% and good sustained-release properties (release time up to 63 h) ensuring sustainable scale inhibition. The scale inhibitor released from the microcapsules could inhibit the growth of calcium carbonate crystals and result in lattice distortion, which contributed to high scale inhibition efficiency (about 86%). The prepared microcapsules have broad application prospects in the field of industrial scale inhibition. • A new way to use scale inhibitors, encapsulation of scale inhibitors, was provided. • A water-soluble scale inhibitor was successfully encapsulated into microcapsules. • Melamine-formaldehyde shell was used to encapsulate aqueous solution. • The microcapsules possessed high encapsulation efficiency. • The microcapsules possessed high scale inhibition efficiency.

Research on performance optimization and mechanism of electrochemical water softening applied by pulse power supply.

In order to promote the application of electrochemical water softening technology in industrial circulating cooling water systems, electric field type, cathode structure and solution residence time are selected for optimization analysis of an electrochemical water softening device. The experimental results show that the water softening performance per unit area of mesh cathode is better than that of a plate cathode. In addition, the softening amount per unit area of the mesh cathode can be further increased when the high-frequency (HF) power supply is applied. When the HF power supply is applied, the softening amount per unit area is 158.58 g/m2·h-1 more than when the direct current power supply is applied. In order to explore the growth mechanism of calcium carbonate, micro-analysis technology and high-speed bubble photography technology are used. The results show that the bubbles escape along the longitudinal direction of the electrode plate, and the main growth direction of calcium carbonate growth is consistent with the escape direction of the bubble; that is, the bubbles grow along the longitudinal direction of the electrode plate. The special structure of the diamond-shaped mesh cathode facilitates the growth of calcium carbonate crystals.

Functional analyses of chitinolytic enzymes in the formation of calcite prisms in Pinctada fucata

The mollusk shells present distinctive microstructures that are formed by small amounts of organic matrices controlling the crystal growth of calcium carbonate. The shell of Pinctada fucata has the prismatic layer consisting of prisms of single calcite crystals and the nacreous layer consisting of aragonite tablets. The calcite crystal of prisms contains small angle grain boundaries caused by a dense intracrystalline organic matrix network to improve mechanical strength. Previously, we identified chitin and chitinolytic enzymes as components of this intracrystalline organic matrix. In this study, to reveal the function of those organic matrices in calcium carbonate crystallization, calcites synthesized in chitin gel with or without chitinolytic enzymes were analyzed by using transmission electron microscope (TEM) and atom probe tomography (APT), showing ion clusters derived from chitin inside of a calcite and small angle grain boundaries at optimal chitinolytic concentration. Furthermore, we performed the experiment in which chitinase inhibitor was injected into a living P. fucata. Nanoindentation and electron back scattered diffraction (EBSD) show that mechanical properties and crystal orientation were changed. These results suggested that chitinolytic enzymes work cooperatively with chitin to regulate the crystal growth and mechanical properties of the prismatic layer.

Investigation of Crystal Growth in Enzymatically Induced Calcite Precipitation by Micro-Fluidic Experimental Methods and Comparison with Mathematical Modeling

Enzymatically induced calcite precipitation (EICP) is an engineering technology that allows for targeted reduction of porosity in a porous medium by precipitation of calcium carbonates. This might be employed for reducing permeability in order to seal flow paths or for soil stabilization. This study investigates the growth of calcium-carbonate crystals in a micro-fluidic EICP setup and relies on experimental results of precipitation observed over time and under flow-through conditions in a setup of four pore bodies connected by pore throats. A phase-field approach to model the growth of crystal aggregates is presented, and the corresponding simulation results are compared to the available experimental observations. We discuss the model’s capability to reproduce the direction and volume of crystal growth. The mechanisms that dominate crystal growth are complex depending on the local flow field as well as on concentrations of solutes. We have good agreement between experimental data and model results. In particular, we observe that crystal aggregates prefer to grow in upstream flow direction and toward the center of the flow channels, where the volume growth rate is also higher due to better supply.

Research on the feasibility of strengthening the soil structure by biomineralization

ABSTRACT The objective of the present study is to explore the feasibility of strengthening soil structures using the microbe induced calcium carbonate precipitation (MICP) method. In the tests that have been conducted, the work has simulated soil structures using standard sand, producing test specimens with relative densities of Dr = 40%, 60% and 80%. The MICP test results indicate that Sporosarcina pasteurii induced the precipitation of calcium carbonate through a metabolic pathway, which enables the growth of calcium carbonate crystals between the sand particles to perform infilling and cementation. After conducting the MICP treatment, the originally non-cohesive standard-sand specimens could be consolidated into blocks, and the test specimens subjected to MICP treatment over longer durations exhibited better overall cementation. The unconfined compressive strengths of the specimens increased from 0 kPa (the compressive strength of a loose sand specimen) to become approximately 3 ~ 12 kPa. This result indicates that the MICP method can result in cohesion using a standard-sand test specimen and will strengthen the sand’s structure. The resonant column test results show that the shear-wave speed depicts a significant increase, which further demonstrates that the specimen structure is considerably strengthened using the MICP treatment.

Identification of methionine -rich insoluble proteins in the shell of the pearl oyster, Pinctada fucata

The molluscan shell is a biomineral that comprises calcium carbonate and organic matrices controlling the crystal growth of calcium carbonate. The main components of organic matrices are insoluble chitin and proteins. Various kinds of proteins have been identified by solubilizing them with reagents, such as acid or detergent. However, insoluble proteins remained due to the formation of a solid complex with chitin. Herein, we identified these proteins from the nacreous layer, prismatic layer, and hinge ligament of Pinctada fucata using mercaptoethanol and trypsin. Most identified proteins contained a methionine-rich region in common. We focused on one of these proteins, NU-5, to examine the function in shell formation. Gene expression analysis of NU-5 showed that NU-5 was highly expressed in the mantle, and a knockdown of NU-5 prevented the formation of aragonite tablets in the nacre, which suggested that NU-5 was required for nacre formation. Dynamic light scattering and circular dichroism revealed that recombinant NU-5 had aggregation activity and changed its secondary structure in the presence of calcium ions. These findings suggest that insoluble proteins containing methionine-rich regions may be important for scaffold formation, which is an initial stage of biomineral formation.

Performance of green antiscalants and their mixtures in controlled calcium carbonate precipitation conditions reproducing industrial cooling circuits

Cooling circuits in many industrial sectors are faced with daily issues of scaling. One preventive treatment consists in injecting a polymer additive in the circuit to inhibit precipitation of calcium carbonate. Among the used additives, very few are “green” and the efficiency of new candidates are difficult to test directly in industrial conditions. The present study compared performance between two “green” polymer additives, polyaspartic acid (PASP) and polyepoxysuccinic acid (PESA), versus a traditional gold-standard, homopolymer of acrylic acid (HA) in a laboratory scale set-up designed to be representative of an industrial circuit. Results showed that HA and PASP are both inhibitors of calcium carbonate crystal growth. This inhibition resulted from adsorption of polymer additive molecules on the crystal surface, as confirmed by adsorption measurement. Under the same conditions, PESA additive, showed a high rate of calcium ion complexation and a very low inhibition rate. But, PESA was shown to be a nucleation delayer. Mixing PESA and PASP can gave nucleation retardation of about 19 h, which approximates the 24 h water residence time in industrial cooling circuits, as well as almost 90% calcium carbonate crystal growth inhibition. This synergy offers promising prospects for preventive scaling treatment.

Surfactin as a Green Agent Controlling the Growth of Porous Calcite Microstructures.

This study presents a new, simple way to obtain mesoporous calcite structures via a green method using an eco-friendly surface-active compound, surfactin, as a controlling agent. The effects of synthesis time and surfactin concentration were investigated. The obtained structures were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) coupled with gas mass spectrometry (QMS) analysis. The experimental data showed that surfactin molecules significantly changed the morphology of the calcite crystals, roughening and deforming the surface and creating a greater specific surface area, even at low biosurfactant concentrations (10 ppm). The size of the crystals was reduced, and the zeta potential value of calcium carbonate was more negative when more biosurfactant was added. The XRD data revealed that the biomolecules were incorporated into the crystals and slowed the transformation of vaterite into calcite. It has been shown that as long as vaterite is present in the medium, the calcite surface will be less deformed. The strong influence of surfactin molecules on the crystal growth of calcium carbonate was due to the interaction of surfactin molecules with free calcium ions in the solution as well as the biomolecules adsorption at the formed crystal surface. The role of micelles in crystal growth was examined, and the mechanism of mesoporous calcium carbonate formation was presented.

Anatomy and Jurassic evolution of a Hercynian basement high (Caloveto High - Calabria, Southern Italy)

The Caloveto area in North-East Calabria hosts a stratigraphic succession which documents the evolution from shallow water carbonates to deeper-water pelagic and hemipelagic deposits, bearing ample evidence for severe tectonic control on Jurassic and Lower Cretaceous sedimentation. Geological mapping indicates that the shallow-water carbonates, also with coral assemblages, formed a narrow fringe around a high of the Hercynian basement, made of lowgrade metamorphic rock, which remained emergent throughout the Pliensbachian and became an intrabasinal high which stood proud of the Longobucco basin, hosting thin pelagic sedimentation through most of the Jurassic. An extensional phase in the Toarcian disrupted and foundered the benthic carbonate factory, whose drowning isdocumented by a change to Rosso Ammonitico-type deposits. This resulted in a complex network of neptunian dykes (also intruding the basement) and in-situ breccias. Starting in the late Toarcian, the rugged submarine topography was gradually leveled by onlapping marls, radiolarites and pelagic limestone, which sealed the Toarcian fault zones producing a diverse array of unconformities. Colonization by microbial communities characterizes the initial stages ofmarine sedimentation around the cores of Paleozoic basement, as banded polychrome microbialites and “swollen” phyllites, a result of the microbially-influenced/induced displacive growth of calcium carbonate crystals along split cleavage planes, constitute an unexpected field tool for identifying basin margins. Silicified marginal zones in the shallow water limestone characterize, in analogy withother Tethyan regions, the onlap unconformities of chert-rich basinal units on the submerged carbonate fringes.

ВЛИЯНИЕ КАРБОНАТА НАТРИЯ НА ПРОЦЕСС ТВЕРДЕНИЯ ПОРТЛАНДЦЕМЕНТНОГО КОМПОЗИТА

The article enlightens a number of chemical transformations during hydration of Portland cement blended with sodium carbonate. Excess of ions CO3 in solution slows down the development of portlandite (calcium hydroxide) and provide intensive growth of calcium carbonate (calcite) crystals in hydrated cement, especially during the first day of hardening. It is shown that there are differences in strength between the solidified Portland cement mixture without and with the addition of Na2CO3. Soda modifies the procedure for the entry into the hydration reaction of the clinker components of the cement. With a certain increase in its content in the mixture, a slight increase in cubic strength for the dry-hardening specimens is also observed.

Effect of pH and temperature on calcium carbonate precipitation by CO2 removal from iron‐rich water

AbstractIn the present work, the effect of temperature and solution pH on calcium carbonate precipitation from iron‐rich waters was investigated. Calcium carbonate was precipitated by CO2 removal. The increase in the temperature or the solution pH leads to the acceleration of calcium carbonate nucleation and crystal growth. Iron addition retards the formation of calcium carbonate crystals and enhanced the precipitation in the bulk solution. At high supersaturations, the inhibition effectiveness of iron is small and it could be improved by lowering the solution pH. The results of the present work show that it is possible to reduce or completely prevent scale formation in different water treatment processes by controlling the operating parameters which favourably affects the water treatment costs, increases the equipment life and allows increased product water recovery.

Effect of setting accelerator additive on short- and long-term properties of cold recycled mixture containing bitumen emulsion–cement composites

Cold recycled layers have low early stiffness and are prone to rutting at initial days of curing. In this research, it was tried to resolve these issues by concurrent use of cement and chloride-free sodium carbonate-based accelerator. The cement content was fixed to 2% by weight of dry reclaimed asphalt pavement. The accelerator contents varied from 0% to 15% of the cement weight at 5% intervals. Experimental study was conducted on recycled mixes and emulsion–cement pastes. The partial and full curing protocols have been used to simulate the short- and long-term field curing processes, respectively. Marshall stability, indirect tensile strength and resilient modulus tests were accomplished on recycled mixes after both curing protocols and indirect tensile fatigue test was performed after the full curing process. Micro-structural analysis including the X-ray diffraction and scanning electron microscopy were conducted on cured pastes. Furthermore, the hydration heat release was measured by isothermal calorimetric procedure. It was concluded that the existence of emulsion in cement paste to some extent hindered the cement–water reactions. The addition of accelerator evidently increased the rate of cement hydration at initial days of curing and compensated the retarding effects of emulsion. For partially cured specimens, the strength and stiffness of recycled mixes containing accelerator was higher than the conventional mixture. However, a significant decrease in stiffness occurred after finishing the curing process for accelerator containing mixes. The retardation in portlandite development and growth of calcium carbonate crystals were the main reasons for stiffness decrease in these mixes after the full curing process.