Kinetics Of CaCO3 Precipitation Research Articles

Unlocking high carbonation efficiency: Direct CO2 mineralization with fly ash and seawater

Direct CO2 mineralization using fly ash is a promising technology to achieve CO2 sequestration. Seawater's abundance and calcium-rich composition make it an attractive substitute solution for CO2 sequestration. However, there have been limited studies conducted so far, and the mineralization mechanism remains unclear, which has constrained its industrial application potential. Here we utilized low CaO-content fly ash in combination with seawater to perform direct CO2 mineralization under ambient conditions, achieving a remarkable carbonation efficiency of 94.8 %. Upon scrutinizing the carbonate parameter evolution, we identify a crucial pH range (8.2 ∼ 10.4) that enhances calcium elution efficiency, leading to heightened carbonation efficiency. The involvement of Mg(OH)2 within this pH range influences CaCO3 precipitation kinetics and crystalline phase. This innovative approach holds promise for carbon sequestration and presents a valuable contribution to sustainable CO2 utilization strategies.

The role of phosphate on non-skeletal carbonate production in a Cretaceous alkaline lake

Alkaline carbonate-rich systems may, under some circumstances, result in significant accumulation of aqueous phosphorus. Additionally, the geochemistry of modern alkaline lakes, combined with current understanding of CaCO3 precipitation kinetics, indicates that the establishment of high alkalinity, high dissolved inorganic carbon (DIC), and CaCO3 supersaturation require compounds that inhibit or interfere with CaCO3 precipitation. Furthermore, the interplay between these factors may potentially affect fabric development in non-skeletal carbonates. In order to understand how these interlinked processes may have regulated PO4 concentrations and the processes and products of non-skeletal CaCO3 precipitation in the distant past, we conducted a detailed geological and geochemical study in two cores drilled in different portions of the Santos Basin, offshore southeastern Brazil, consisting of lacustrine carbonate rocks from the Lower Cretaceous Barra Velha Formation. We find that phosphorus in the sediments comes from two main products, phosphatic bioclasts and authigenic phosphate (of both primary and diagenetic origins). We also find that phosphorus occurs in concentrations of up to several thousand ppm in some intervals and is preferentially associated with some calcite textures potentially reflecting the primary sedimentary depositional conditions (e.g., upward-radiating aggregates of fibrous calcite, or “shrubs” and spherulitic aggregates of fibrous calcite, or “spherulites”). Microanalytical data from selected samples and high-Mg CaCO3 textures show median P values can be particularly high in crusts, shrubs and spherulitic calcite minerals interpreted here to have formed as primary to early diagenetic deposits, and roughly vary between 1000 and 2000 ppm (10.5–21.1 mmol/kg). The average P/(Ca + Mg) molar ratio values based on the same data for these three calcite textures are 1.45 ± 0.98, 1.13 ± 0.97 and 1.09 ± 0.90 mmol/mol, respectively, being as high as 4.80 mmol/mol in specific spots in “shrubby” textures. Although multiple source-to-sink mechanisms were likely involved in the P budget in lake waters and in the sediments, such as recycling and remobilisation of skeletal- and organic-bound phosphate, high alkalinity may have enhanced its accumulation in the lake’s waters. In light of current understanding of CaCO3 precipitation kinetics, we hypothesise that phosphate may have played a central role in maintaining high calcium carbonate saturation (14–45 < Ωcalcite ≤ 100–180). These conditions would have favoured growth of calcite crystals on pre-existing substrates over nucleation of finely particulate carbonate sediment. By combining these observations with theoretical geochemical considerations, we propose that phosphate inhibition of calcium carbonate precipitation was enhanced by high alkalinity, further sustaining CaCO3 supersaturation and favouring distinctive carbonate growth textures. This unique and relatively well-preserved example of non-skeletal carbonate production implies that similar regulation of CaCO3 precipitation kinetics and PO4 concentrations may have operated across other intervals of time in Earth’s history, both in non-marine and marine environments that pre-date the emergence of skeletal calcification.

Kinetics of CaCO3 precipitation in seeded aeration softening of brackish water desalination concentrate

Desalination of brackish water is energetically attractive, but the concentrate produced poses a major environmental issue. Intensive research has been carried out to develop demineralization techniques of such concentrates to facilitate their utilization and disposal. Aeration was reported to allow chemical-free and effective demineralization through CaCO3 precipitation. When applied in concentrate treatment, the process was assumed to follow first order kinetics, but second order kinetics were proposed when the process was applied in potable groundwater treatment. In the current study the effect of aeration rates and seed concentration on reaction kinetics was studied in real brackish water desalination concentrates (BWDC). In the absence of or at low aeration, CaCO3(s) precipitation followed second order kinetics characteristic of simple CaCO3(s) precipitation. With increasing aeration rate, the reaction shifted toward first order kinetics, characteristic of gaseous CO2 release. Both aeration rate and seed concentration linearly increased the gas mass transfer coefficient. Under the experimental conditions, maximal removal rate was 1.05 g calcium-CaCO3 L−1 h−1. Calcium removal reached 73% and was found to depend on raw concentrate composition and reaction time. The composition of the softened concentrate corresponded well with the geochemical PHREEQC code simulation of the solution at equilibrium. The precipitates comprised at least 92% calcite, which may be of economic significance. The ability to use the intrinsic precipitates as seed particles may be advantageous in terms of CaCO3 recovery and simplicity of operation.

Mineralogical constraints on Neoproterozoic pCO2 and marine carbonate chemistry

Abstract Numerous investigators have sought to identify the perturbations to the global carbon cycle that fueled Earth system change during the Neoproterozoic Era. Nevertheless, a lack of constraints on ocean-atmosphere carbon chemistry has precluded efforts to link biology, climate, and the lithosphere. We combined field and petrographic observations with experimental and theoretical geochemistry to show that early Neoproterozoic seawater featured elevated alkalinity in the presence of high atmospheric pCO2, which sustained remarkable marine CaCO3 supersaturation (Ωcalcite). Without pelagic calcification, Neoproterozoic marine Ωcalcite and pCO2 would have been mediated principally by CaCO3 precipitation kinetics; thus, secular changes in kinetic inhibitors to CaCO3 nucleation may have destabilized the global carbon cycle.

Impact of bacteria and urease concentration on precipitation kinetics and crystal morphology of calcium carbonate

Microbial/Enzyme-induced carbonate precipitation uses bacteria/urease to drive the biogeochemical reactions to generate CaCO3 precipitation. The goal of this study was to assess the impact of initial concentrations of urease and bacteria on precipitation kinetics and crystal morphology (crystal shape and chemical composition) of calcium carbonate precipitation. Experimental results showed that the CaCO3 precipitation kinetics were well-fitted by a modified exponential logistic model with a confidence value of 95%, and higher concentrations of bacteria and urease could increase the precipitation rate of CaCO3. The results of XRD, FTIR and SEM indicated that vaterite phase was the dominant form of CaCO3 crystals in bacteria-induced system, and calcite phase was the primary form of the CaCO3 crystals in urease-induced system. The results also showed that the effect of initial concentrations of bacteria and urease on the morphology of CaCO3 crystals was insignificant.

The kinetics, thermodynamics and mineral crystallography of CaCO3 precipitation by dissolved organic matter and salinity

Calcium carbonate (CaCO3) precipitation is an important geochemical process. In the estuary zone and some arid shallow lakes, DOM (dissolved organic matter) and salinity are two frequent changing factors that may affect CaCO3 precipitation. The joint effect of DOM and salinity on CaCO3 precipitation kinetics and thermodynamics are still unclear. In this study, effects of DOM on CaCO3 precipitation process at 0.5‰ and 70‰ salinity were investigated by QCM (Quartz Crystal Microbalance) technique, real-time pH measurement and single-injection nanoliter ITC (isothermal titration calorimetry). The mineral crystallography was analyzed by SEM-EDS. Both DOM and salinity had inhibitory effect on CaCO3 precipitation. DOM had more pronounced inhibitory effect on CaCO3 precipitation at lower salinity. Regardless of DOM, 70‰ salinity inhibited CaCO3 precipitation >0.5‰ salinity. The CaCO3 precipitation kinetics followed the first-order kinetic model and the adhesion kinetics of the instantaneous nucleation and crystal growth stage could be well described by the exponential function. CaCO3 precipitation was an endothermic process and high salinity strongly hindered CaCO3 precipitation. The effect of DOM on the absorbed heat was significant at 0.5‰ salinity. At 70‰ salinity, regardless of the effect of DOM, CaCO3 precipitation rate was greatly slowed down because it needed much more heat. CaCO3 minerals were dominated by rhombohedral calcite while CaCO3 minerals were mainly shaped as spherical vaterite at 0.5‰ salinity and rhombohedral calcite at 70‰ salinity. The crystal phase changed during CaCO3 precipitation at 0.5‰ salinity. In conclusion, the presence of DOM had substantial impact on the micrograph of the CaCO3 minerals. The percentage of flawed crystals with rough surface increased significantly with increased DOM concentration.

A new potential of calcium carbonate production induced by Bacillus sphaericus in batch fermentation

Bacteria is believed to induce calcium carbonate precipitation as it meets the concept of bioconcrete. Bacillus sphaericus was found to produce enzyme urease capable to hydrolyse urea, thus generate carbonate ions. The excess presence of calcium ions in the system will precipitate calcium carbonate. Therefore, the used of bioreactor to produce calcium carbonate can meet the demand for calcium carbonate as it can be produced in large-scale production thus maximize the production of calcium carbonate. The aim of this paper conducted by using 2.5 L bioreactor was to investigate the precipitation of CaCO3 and to optimize the production of H2CO3 by using different parameters such as agitation and aeration. As this is a preliminary study, the artificial urea is used as the carbon source of the Bacillus sphaericus. The determination of the kinetics of CaCO3 precipitation in the 2.5 L batch bioreactor such as specific growth rate (μ) and doubling time (Td) were studied after fermentations were stopped. The composition of calcium carbonate characteristic from the fermentation of Bacillus Sphaericus in 2.5 L bioreactor of pH 8.0 and 30 °C were proved by X-Ray Diffraction. The highest specific growth rate (0.141 h-1) was obtained. The optimum parameters condition to produce bicarbonate ions and calcium carbonate was at 50 rpm with 2.0 vvm aeration rate

Krystalizatsiya karbonatu kal'tsiyu z hidrokarbonatnykh rozchyniv

The kinetics of CaCO3 precipitation from model solutions formed by preliminary saturating deionized water with CO2 and by adding NaHCO3 and CaCl2 has been considered. The characteristic feature of the method is the almost simultaneous measurement of the activities of major components of the aqueuos calcium hydrocarbonate system (ACHCS): Ca2+, CO2, HCO−3 , as well as pH and the temperature. CaCO3 crystallization was provided with the help of the CO2 degassing by air. The processes running in the ACHCS during the degassing can be divided into four stages: dissociation of CaHCO+3 complexes; formation of crystal nuclei in the solution; a transitive stage, which includes the final phase of crystal nucleation and the initial growth of newly formed crystals; and intensive growth of crystal nuclei, which gives rise to the mass CaCO3 precipitation. The product (Ca2+)·(CO2−3 ) is a reaction coordinate for the second stage of CaCO3 precipitation, whereas (Ca2+)·(HCO−3 ) for the third and fourth stages. The kinetics of growth of crystal nuclei and their concentration are calculated for the second stage, by using the concept of CaCO3 dissolution product that depends on the crystal nucleus size. During the process of crystal nucleation, the crystal size remains practically stable (≈8×10^−8 m), and the concentration reaches 1.5×10^−15 m−3. The mass CaCO3 precipitation (the fourth stage) starts when the crystal nuclei reach dimensions of about 3×10^−7 m.

Kinetics of CaCO3 precipitation in an anaerobic digestion process integrated with silicate minerals

Integration of silicate minerals in the anaerobic digestion (AD) process has recently been proposed as a way to sequester CO2, neutralize the pH and produce biobased products such as biogas and biofertilizers. The objective of this study was to investigate the kinetics of CaCO3 precipitation in an anaerobic digestion process integrated with a silicate mineral (wollastonite).The first series of experiments studied the precipitation kinetics during the methanogenic phase by addition of calciumacetate to anaerobic batch reactors. CaCO3 precipitation initiated when the ion activity product of Ca2+ and CO32− exceeded calcium carbonate monohydrate solubility product (Ksp of 5.7×10−8 at 35°C). Addition of calcite seed crystal at the start of the experiment showed that the precipitation could be initiated earlier by reducing the induction period. In these experiments, precipitation of CO2 in the form of CaCO3 showed an 52% increase in CH4 content of the biogas (71±0.5% v/v CH4) compared to that of the control experiment fed with sodium acetate (53±0.5% v/v CH4).In the second set of experiments, single-stage anaerobic batch digestions with 25g/l wollastonite (63–125μm) at two different substrate concentrations (5.5g/l and 17.5g/l insoluble starch) were studied. In these experiments the main processes of wollastonite dissolution and calcite precipitation occurred, however the limited separation of fermentation and methanogenesis phases resulted in a limited increase in methane content of the biogas. Although the precipitation was observed at lower supersaturation, the crystal growth followed the same pattern as in previous experiments with calcium acetate. In both sets of experiments, a self-regulating pH could be achieved in the system as the result of the presence of wollastonite which caused the pH to remain in the range of 5.7–7.9. Obtaining an improved biogas and a self-regulated pH in a digester contribute to the advantages of CO2 sequestration by means of silicate minerals in anaerobic digestion systems.

Kinetics of calcium carbonate precipitation through CO2 absorption from flue gas into distiller waste of soda ash plant

Kinetics of CaCO3 precipitation by CO2 absorption from flue gas into distiller waste of soda ash plant was investigated by minimizing the differences between the model predictions and experimental data through a method of genetic algorithm. A population balance equation coupled with a mass balance equation was used to model CaCO3 precipitation. These model equations were solved using the numerical method of Crank–Nicolson. Impurities in distiller waste and different concentrations of CO2 in synthetic flue gas were found to be influential in mechanisms of nucleation, growth and agglomeration of CaCO3 precipitates. The impurities increased the agglomeration but reduced the nucleation and growth rates.

Influence of enzyme concentration on bio-sequestration of CO2 in carbonate form using bacterial carbonic anhydrase

One of the most promising biological sequestration technologies of CO2 is the enzyme catalyzed CO2 sequestration into stable and environmentally friendly mineral carbonates. The present manuscript focused on the biocatalytic precipitation of CaCO3 by extracellular carbonic anhydrase (CA) which was extracted and purified from the culture of Bacillus cereus. The kinetics of CaCO3 precipitation catalyzed by the bacterial CA in the presence of different enzyme concentrations was investigated through the gaseous diffusion system. The polymorph and morphology of CaCO3 crystals obtained in the precipitation process were also analyzed using XRD, FTIR and FESEM. The results showed that the change in the amount of deposited Ca2+ during the process of CaCO3 precipitation catalyzed by bacterial CA of different concentrations was well fitted with the exponential model. The enzyme concentrations of 0.2–2.0U/mL were beneficial to CaCO3 precipitation, however, overhigh enzyme concentration (8.0U/mL) was not conducive to CaCO3 precipitation. The integrated results of XRD, FTIR and FESEM analysis showed that there were significant differences in the morphologies of CaCO3 crystals among different enzyme concentrations. Vaterite was present at the lower concentration of CA, and the higher concentration of CA favored the formation of calcite. Therefore, different polymorphs and morphologies of CaCO3 crystals can be produced in the presence of different concentrations of CA. Furthermore, the role of bacterial CA in CaCO3 precipitation was related to the electrostatic adsorption of Ca2+ on CA enzyme protein and the preferential adsorption of CA enzyme protein on the crystal faces, in addition to the enzymatic catalysis.

Effects of temperature on precipitation kinetics and microstructure of calcium carbonate in the presence of magnesium and sulphate ions

In the present work, the effects of the temperature on the kinetics and microstructure of CaCO3, precipitated in the presence of magnesium and sulphate ions, were studied using degassing dissolved CO2 method. The precipitates were identified by X-ray diffraction, atomic absorption spectroscopy and scanning electron microscopy. It was shown that at fixed temperature and ionic strength, the presence of sulphate and magnesium ions increased the induction time, decreased the crystal growth rate and reduced the amount of the CaCO3 precipitates obtained. Magnesium induced the formation of aragonite form rather than the calcite and vaterite form. The increase of temperature in presence of magnesium and sulphate ions lead to a change on the effect of magnesium on kinetics of CaCO3 precipitation and caused the Mg2+ ions incorporation in the CaCO3 lattice. The increase of temperature favoured the aragonite phase in magnesium solutions and both aragonite and vaterite in presence of sulphate ions.

Influence of initial calcium ion concentration on the precipitation and crystal morphology of calcium carbonate induced by bacterial carbonic anhydrase

Biogenic precipitation of calcium carbonate (CaCO3) has attracted much attention due to its role in many geological processes, applications of Geological and Civil Engineering as well as environmental treatments. The present paper focused on the biocatalytic precipitation of CaCO3 by the extracellular carbonic anhydrase (CA) extracted and partially purified from the culture of Bacillus cereus. The kinetics of CaCO3 precipitation catalyzed by the bacterial CA at different initial concentrations of Ca2+ (C0(Ca2+)) was investigated through the gaseous diffusion system. The polymorph and morphology of CaCO3 crystals obtained in the precipitation process were also analyzed using XRD, FTIR and FESEM. The results showed that in the process of CaCO3 precipitation catalyzed by bacterial CA, the change in the amount of deposited Ca2+ at different C0(Ca2+) fitted well with the exponential model. Greater fluctuation of pH occurred in the water control group during the rising process of pH, while in the CA group the pH increased more steadily. This may be related to the role of CA in pH regulation. The precipitation rate of CaCO3 increased with the increasing C0(Ca2+), but overhigh C0(Ca2+) of 100mmol/L had a certain negative influence on CaCO3 precipitation catalyzed by bacterial CA. The integrated results of XRD, FTIR and FESEM analysis showed that the C0(Ca2+) had greater effect on the polymorph and morphology of CaCO3 crystals formed in the presence of bacterial CA. The lower C0(Ca2+) favored the formation of vaterite and the higher C0(Ca2+) favored the formation of calcite.

The Effect of the CO32- to Ca2+ Ion activity ratio on calcite precipitation kinetics and Sr2+ partitioning.

BackgroundA proposed strategy for immobilizing trace metals in the subsurface is to stimulate calcium carbonate precipitation and incorporate contaminants by co-precipitation. Such an approach will require injecting chemical amendments into the subsurface to generate supersaturated conditions that promote mineral precipitation. However, the formation of reactant mixing zones will create gradients in both the saturation state and ion activity ratios (i.e., ). To better understand the effect of ion activity ratios on CaCO3 precipitation kinetics and Sr2+ co-precipitation, experiments were conducted under constant composition conditions where the supersaturation state (Ω) for calcite was held constant at 9.4, but the ion activity ratio was varied between 0.0032 and 4.15.ResultsCalcite was the only phase observed, by XRD, at the end of the experiments. Precipitation rates increased from 41.3 ± 3.4 μmol m-2 min-1 at r = 0.0315 to a maximum rate of 74.5 ± 4.8 μmol m-2 min-1 at r = 0.306 followed by a decrease to 46.3 ± 9.6 μmol m-2 min-1 at r = 1.822. The trend was simulated using a simple mass transfer model for solute uptake at the calcite surface. However, precipitation rates at fixed saturation states also evolved with time. Precipitation rates accelerated for low r values but slowed for high r values. These trends may be related to changes in effective reactive surface area. The ratios did not affect the distribution coefficient for Sr in calcite (DPSr2+), apart from the indirect effect associated with the established positive correlation between DPSr2+ and calcite precipitation rate.ConclusionAt a constant supersaturation state (Ω = 9.4), varying the ion activity ratio affects the calcite precipitation rate. This behavior is not predicted by affinity-based rate models. Furthermore, at the highest ion ratio tested, no precipitation was observed, while at the lowest ion ratio precipitation occurred immediately and valid rate measurements could not be made. The maximum measured precipitation rate was 2-fold greater than the minima, and occurred at a carbonate to calcium ion activity ratio of 0.306. These findings have implications for predicting the progress and cost of remediation operations involving enhanced calcite precipitation where mineral precipitation rates, and the spatial/temporal distribution of those rates, can have significant impacts on the mobility of contaminants.

Efficiency assessment of inhibitors on CaCO3 precipitation kinetics in the bulk and deposition on a stainless steel surface (316 L)

Calcium carbonate (CaCO3) is a common type of scale. Since the beginning of the XXe century, chemical inhibitors, such as PolyphosphinoCarboxylic acid (PPCA), were used to reduce and suppress the scale precipitation, assuming that it would act in the same way on scale deposition on surfaces. Desalination plants and oil industries are currently facing severe restrictions concerning the discharge of oilfield chemicals into the environment. CarboxyMethyl Inulin (CMI), PolyAspartate (PA) and PolyMaleic Acid (PMA) are three inhibitors commonly referred to as “green” products. This paper compares the effect of these inhibitors on the CaCO3 bulk precipitation and deposition on the surface of austenitic stainless steel (316L), at 70°C, under a controlled turbulent flow regime. This study shows that calcium carbonate full inhibition requires higher concentrations for scale deposition than for scale precipitation. Green inhibitors require higher concentrations to reach PPCA inhibition efficiency on both calcium carbonate formation mechanisms.

Étude expérimentale de la précipitation des carbonates de calcium en présence de l'ion magnésium

The precipitation of calcium carbonate is studied as a function of the change of partial pressure of CO₂. The experimental results of the kinetics of CaCO₃ precipitation are reported. The influence of the magnesium ion in a solution initially containing 360 mg l⁻¹ of Ca²⁺ and containing increasing amounts of MgCl₂ • 6H₂O (from 0 to 1 080 mg l⁻¹ Mg²⁺) is reported on : — the nucleation time, — the initial growth rate, — the allotropie variety and the shape of the crystals. The magnesium ion moves the equilibrium system to the right and the aragonite form is precipitated. As for the crystals of calcite which remain, dosages by atomic absorption and X-rays show a calcite containing more and more magnesium as the concentration of Mg²⁺ in the solution increases.