Role of Aspartic Acid in the Synthesis of Spherical Vaterite by the Ca

Article pubs.acs.org/crystal

Role of Aspartic Acid in the Synthesis of Spherical Vaterite by the Ca(OH)2−CO2 Reaction Jia Luo, Fantao Kong, and Xinsheng Ma* National Engineering Research Center of Ultrafine Powder, School of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, P. R. China ABSTRACT: Vaterite crystals with a spherical shape were successfully obtained by the addition of aspartic acid (Asp) in the calcium hydroxide (Ca(OH)2)−carbon dioxide reaction system. Crystalline products were characterized by X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis, and differential scanning calorimetry (TG-DSC). The experimental results indicate that the addition of Asp can inhibit the growth of calcite but promote the formation of vaterite, and the spherical vaterite CaCO3 is gradually dominant along with the increase of Asp. Meanwhile the content of the vaterite phase is prominently influenced by the reaction temperature, and the optimal temperature for vaterite is at 40 °C. It is proposed that vaterite is induced through the intermediate chelated by Asp and Ca(OH)2, and then Asp is adsorbed on the surface of vaterite by chelation, preventing the metastable vaterite from transforming to calcite via a dissolution−recrystallization process. Further, the decrease of pH in the solution could reduce the chelation between Asp and Ca2+, leading to the transformation from vaterite to calcite. Hence, the study on the formation and transformation of vaterite will provide additional insight into biomineralization mechanism and industrial production.

1. INTRODUCTION Biomineralization is a widespread phenomenon in nature, which leads to the formation of a variety of organic−inorganic structures in living organisms.1 Calcium carbonate is one of the most abundant minerals in nature. In recent decades, it has had a wide application as a coating pigment, filler, and extender in the production of plastics, paper, rubber, textiles, adhesives, paints detergents, and medicines,2−4 which is determined by its physicochemical and structural properties such as the pore size distribution, specific surface area, brightness, adsorption capacity, and chemical purity.5,6 As we know, there are three anhydrous crystalline polymorphs of CaCO3: rhombohedral calcite, orthorhombic aragonite, and hexagonal vaterite.7 Therein, calcite is thermodynamically the most stable form, followed by aragonite and vaterite. In biological systems, the vaterite phase has been found in fish otoliths, healed scars of some mollusk shells, gallstones, and freshwater pearls.8,9 In different circumstances, some additives could stabilize the vaterite and delay its transformation into aragonite or calcite. Vaterite mainly exists in organisms, rather than in nature. So as additives, amino acids with biocompatibility have received great attention for the crystallization and growth of vaterite CaCO3. Tong et al. found that Asp could control the nucleation and the growth of crystallization on increasing the rate of nucleation and delaying the growth of crystal.10 Manoli and Dalas studied the kinetics of vaterite crystallization in the presence of glutamic acid and estimated the number of ions forming the critical nucleus and the surface energy.11 Hood et © 2015 American Chemical Society

al. evaluated the inhibition of nucleation and growth of CaCO3 with different residue acidities by monitoring turbidity and calcium concentration, and found that the stabilization of vaterite followed the order Asp > Glu > Cys > Ser > His > Leu in accordance with the acidity.12 Yuming Gao et al. successfully prepared the different polymorphs and morphologies of CaCO3 with valine, serine, and arginine, which suggested that the polymorphs and morphologies of CaCO3 might be easily adjusted through the selection of the molecular structures of the organic matrices.13 However, most reports just presented the stable effect of some amino acids on vaterite and the transformation from vaterite to calcite. The role of amino acids on the crystallization behavior is still difficult to understand, and the mineralization mechanism of vaterite CaCO3 does not have a complete, reasonable explanation. In the present study, the Ca(OH)2−CO2 reaction system is used in the synthesis of vaterite CaCO3. In general, the stability of the vaterite polymorph is primarily dependent on the concentration of additives and reaction temperature.14−16 We obtained the spherical vaterite at different Asp concentrations and temperatures. Subsequently, we proved the existence of the intermediate, a chelate with calcium ion and Asp, and studied its effect on the process of CaCO3 crystallization. On the basis of the above results, this article proposes the formation Received: September 14, 2015 Revised: December 4, 2015 Published: December 21, 2015 728

DOI: 10.1021/acs.cgd.5b01333 Cryst. Growth Des. 2016, 16, 728−736

Crystal Growth & Design

Article

inVia Reflex Raman spectrometer with 514.5 nm from 120 to 1200 cm−1. The X-ray diffraction patterns (XRD) of precipitated CaCO3 are measured on a D/max 2550 V using parabolic filter Cu/K-α1 (λ = 1.54056 Å), employing a step size of 0.02°/s with 2θ ranging from 10° to 80°. The relative mole fraction of vaterite and calcite in all precipitated CaCO3 can be calculated by the Rao’s equation:17

mechanism of Asp on the spherical vaterite and its transformation to calcite.

2. EXPERIMENTAL SECTION 2.1. Materials. Calcium hydroxide (Ca(OH)2, AR grade), sodium hydroxide (NaOH, AR grade), aspartic acid (Asp, AR grade), and anhydrous ethanol (AR grade) are purchased from Sinopharm Chemical Reagent Co., Ltd. without further purification. Deionized water was employed to prepare the solution. 2.2. Synthesis of Spherical Vaterite. In general experiments, aspartic acid was dispersed in a Ca(OH)2 clear solution (0.8 L, 0.02 mol/L) in a 1 L beaker with stirring for 30 min at 40 °C. The pH of the solution was adjusted to 11.00 by a NaOH solution. Then, the mixture gas CO2 (40 mL/min) with N2 (160 mL/min) was bubbled into the Ca(OH)2 solution, and the reaction ended with pH 9.0. The precipitated CaCO3 was isolated by filter and washed by anhydrous ethanol, and dried at 40 °C for 24 h. Moreover, the precipitated particles were collected at some special time points during CO2 bubbling to examine the behavior of precipitation reaction. A series of comparative experiments with various concentrations of Asp and reaction temperature were performed, and the corresponding conditions and polymorph of products are listed in Table 1.

XV =

sample

conc of Asp (mM)

temperature (°C)

content of vaterite

content of calcite

1 2 3 4 5 6 7 8 9 10 11

20 20 20 20 20 20 20 20 20 20 20

13.33 20.00 26.67 32.00 40.00 80.00 40.00 40.00 40.00 40.00 40.00

40 40 40 40 40 40 10 20 30 50 60

0 0.129 0.269 0.527 0.678 0.843

1.000 0.871 0.731 0.473 0.322 0.157

(1) (2)

where XC and XV are the mole fraction of calcite and vaterite, respectively. I104 C is the XRD intensity of the 104 plane of calcite and 112 114 I110 V , IV , IV are the XRD intensity of 110 plane, 112 plane, 114 plane of vaterite, respectively. The simultaneous thermal analysis of thermogravimetry and differential scanning calorimetry (TG-DSC) are conducted on the NETZSCH STA449F3, with a heat rate of 10 °C/min in air atmosphere from 20 to 1000 °C. The change of pH and conductivity in the solution is continuously measured by a glass electrode with a built-in reference electrod (DDS-307, PHS-2F).

3. RESULTS AND DISCUSSION 3.1. Influence of Asp Concentration on CaCO 3 Precipitation. In the Ca(OH)2−CO2 reaction system, it is found that different polymorphs and morphologies of CaCO3 are obtained in the presence of Asp. The XRD patterns of the obtained samples with different concentrations of Asp at 40 °C are shown in Figure 1a. It is obvious that sample 1 and sample 2 are mainly composed of calcite particles; meanwhile samples 3−6 comprise a mixture of vaterite and calcite particles. With the increase of Asp concentration, the reflection of calcite (JCPDS card number 72-1652) decreases gradually, and vaterite (JCPDS card number 72-1616) progressively dominates. The content of vaterite and calcite contained in these samples is calculated according to eqs 1 and 2, shown in Figure 1b. All these samples were examined by SEM, shown in Figure 2. SEM images show the morphological change of precipitated particles from cubic shape to spherical shape with increasing concentration of Asp, which shows that calcite is in the majority, aggregating with nanoflakes with a length of about 1.6 μm and thickness of about 0.4 μm. However, the spherical vaterite increases along with the increase of Asp concentration, and vaterite is dominated ultimately. Furtherly, magnified SEM images reveal that these microspheres are composed by the aggregation of numerous primary nanoparticles. And some

ACC ACC 0.530 0.414 0

+ IV112 + IV114 + IC104

XC = 1 − XV

Table 1. Polymorph Properties of CaCO3 Obtained at Various Concentration of Asp and Temperature conc of Ca(OH)2 (mM)

IV110 + IV112 + IV114 IV110

0.480 0.586 1.000

2.3. Characterization. The morphology and size of precipitated CaCO3 are characterized by a field emission scanning electron microscopy (FESEM, Navo Nano SEM450) with the operation acceleration voltage of 3 kV. Fourier transform infrared spectra (FTIR) is recorded on a Nicolet 6700 with a spectrometer from 4000 to 500 cm−1 after KBr pelletization. Raman spectra were conducted on

Figure 1. (a) XRD patterns of the obtained samples at different Asp concentrations, C: calcite, V: vaterite. (b) Mole fraction of different polymorphs at different Asp concentrations. 729



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Figure 2. Typical SEM images of spherical and cubic CaCO3 at different Asp concentrations. Inset: magnified SEM images.

3.2. Influence of Reaction Temperature on CaCO3 Precipitation. Moreover, the polymorph composition of precipitated particles is presented as a function of temperature. The polymorphs of precipitated CaCO3 at different temperature are shown in Figure 3a. Correspondingly, the influence of temperature on the content of CaCO3 polymorphs is shown in Figure 3b. It reveals that the particles consist of amorphous

microspheres are observed to be interconnected with each other, demonstrating a tendency of conglutination or clustering between vaterite particles. In a word, the results of XRD and SEM confirm that increasing the Asp concentration can enhance the stability of vaterite phase, promoting the content of vaterite in the precipitated CaCO3. 730



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Figure 3. (a) XRD patterns of the obtained samples at different temperatures. (b) Mole fraction of different polymorphs at different temperatures. (c) Raman spectra of sample 7, sample 5, sample 11.

the temperature rises. The vaterite polymorph occurs predominantly at middle temperature (40 °C). Elevating the temperature above 50 °C can promote the transformation to calcite. The Raman spectra of ACC, vaterite, and calcite are mentioned in some studies.18−20 The Raman spectrum of ACC shows a band assigned to the symmetric stretching mode at 1078 cm−1, and the lattice mode only one broad peak is between 150 and 300 cm−1. The Raman spectrum of vaterite shows a split peak for the symmetric stretching mode in the range between 1074 and 1090 cm−1, and the peaks at 748 cm−1, 740 cm−1, 301 cm−1, and 268 cm−1 in the Raman spectra are the characteristic peak of vaterite, whereas the peaks at 1086 cm−1, 711 cm−1, 281 cm−1, and 155 cm−1 in the Raman spectra are the characteristic peak of calcite. According to the Raman spectra of sample 7, sample 5, and sample 11 (Figure 3c), the polymorphs of these samples are consistent with XRD patterns. These results indicate that the temperature plays a significant role in the crystallization behavior of CaCO3, in agreement with other researchers on the impact of temperature.7,15 3.3. Mechanism of Asp on Precipitated CaCO 3 Polymorph. To understand the influence of Asp concentration and reaction temperature on CaCO3 polymorphs, we analyzed the primary chemical reactions during the precipitation. In the present study, the synthesis of CaCO3 can be obtained from the following reaction without Asp:

Figure 4. Chemical structure of calcium aspartate.

Figure 5. FT-IR spectra of aspartic acid and intermediate.

calcium carbonate (ACC) at low temperature (10−20 °C) and then transforms to the combination of vaterite and calcite when 731

Ca(OH)2 (aq) ⇌ Ca 2 + + 2OH−

(3)

CO2 (g) ⇌ CO2 (aq)

(4)

CO2 (aq) + OH− ⇌ HCO−3

(5)

HCO3− + OH− ⇌ CO32 − + H 2O

(6)



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Figure 6. (a) XRD pattern and (b) SEM image of precipitated CaCO3, carbonizing from the calcium aspartate. Inset: magnified SEM image.

complex compound could reduce the electric conductivity and pH, due to the decrease of total ion concentration.25 (8)

CaY2 + CO32 − ⇌ CaCO3(V) − 2Y −

(9)

where CaCO3(C) and CaCO3(V) are the calcite and vaterite phase, respectively. HY and Y− are the Asp and Asp ion, respectively. Calcium exists with two forms of ionized calcium Ca2+ and chelated calcium CaY2 in the solution on account of partial ionization of CaY2. We believe that ionized calcium Ca2+ would form calcite CaCO3 in the eq 7, while chelated calcium CaY2 forms vaterite CaCO3 in the eq 9. In order to examine the rationality of the above assumption, we isolated and obtained the white solid intermediate by drying the solution before precipitation. Subsequently, the intermediate is examined its structure by FT-IR spectroscopy, shown in Figure 5. The spectrum shows that there are apparent shifts of peak positions of CaY2 in FT-IR, corresponding to that of Asp. It is found that the characteristic peak at 2084 cm−1 of −NH3+ in Asp disappears, which means that −NH3+ has been involved in bonding.26 And the stretch vibration of −NH2 is shifted to 3450 cm−1. The characteristic absorption peak at 1310 and 1518 cm−1, corresponding to the symmetrical and asymmetrical stretch vibration of −COOH, is shifted to 1420 and 1590 cm−1, respectively.27 Additionally, two new absorption peaks at 530 and 660 cm−1 in the FT-IR spectrum of intermediate, which are stretch vibration absorption peaks of Ca−O and Ca−N coordination bond, indicate that intermediate is a chelate of calcium aspartate. In addition, the mass fraction of calcium in the intermediate, which is titrated by EDTA standard solution, is 12.1%, approaches the theoretical value of 13.1%. Next, we directly dissolved the calcium aspartate with some NaOH solution adjusting pH to 11 and bubbled CO2/N2 into the alkaline solution to generate spherical vaterite (Figure 6), which demonstrates that Asp forms intermediate CaY2 via complexing Ca2+ to induce the crystallization of vaterite in the precipitation. We can attempt to interpret these changes of polymorph composition with the above eqs 3−9. In the Ca(OH)2−CO2 reaction system, eq 7 and eq 9 are a pair of competing reactions, in which the former generates calcite through CO32− capturing ionized calcium Ca2+, while the latter generates vaterite by capturing chelated calcium CaY2. Therein, eqs 3−6 have the same effect on both eq 7 and eq 9. And eq 8, a serial reaction with eq 9, provides CaY2 for eq 9. According to the Chemical Equilibrium Theory, it is beneficial to CaY2 by

Figure 7. Variation of the conductivity of CaY2 solution after the temperature compensation versus the different temperatures at pH 6 and pH 11.

Figure 8. Change in the pH and conductivity of the CaY2 alkaline solution versus the CO2 gas bubbling time.

Ca 2 + + CO32 − ⇌ CaCO3(C)

Ca(OH)2 + 2HY ⇌ CaY2 + 2H 2O

(7)

In clear limewater, Ca(OH)2 ionizes to Ca2+ and OH− completely, which provides sufficient OH− to keep alkaline circumstance and absorbs CO2 gas. Simultaneously, Ca2+ and CO32− forms CaCO3, which contributes to the formation of calcite CaCO3, confirmed by some reports.21−24 However, Asp is added in the Ca(OH)2 aqueous solution, and we suppose that Asp would react with Ca(OH)2 to form the complexation (calcium aspartate, structure in Figure 4) of bidentate amino acid with calcium ion. It is important to note that such a 732



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Figure 9. (a) XRD patterns of precipitated CaCO3 at various elapsed times of CO2 gas bubbling. (b) Raman spectra of sample a, sample c, sample e.

versus the CO2 gas bubbling time. At the beginning of 3 min, the pH and conductivity decrease, but the solution is still clear, and the turbidity ensues because of aggregation of precipitated particles in 180 s. Then with CO2 bubbling advancing, at point A (200 s), the turbidity is more obvious. At point B (300 s), the solution gets entirely muddy and the pH and conductivity decrease rapidly. At point C (460 s), the interim of precipitation reaction, the pH and conductivity still decrease. After point D (660 s), which can be considered to be the end of the precipitation, the conductivity has decreased to the minimum value. Moreover, with the continuous CO2 bubbling, at point E (720 s), the pH slowly decreases but the conductivity remarkably increases due to the partial dissolution of CaCO3 in the solution. Next, the samples are collected from the solution at the point A (sample a), B (sample b), C (sample c), D (sample d), E (sample e), and detected the properties of all samples by XRD, SEM, and Raman spectra. The XRD patterns of the sample a and sample b are considered to be the ACC which results from the simple aggregation of nucleation cluster, as depicted in Figure 9a. Certainly, there is a weak peak of calcite observed in the sample b. After bubbling for 460 s, the vaterite is mostly observed, but the peak intensity decreases gradually along with the time of the CO2 bubbling, and ultimately the calcite dominated. Similarly, the Raman spectra of sampe a, sample c, sample e are in agreement with their XRD patterns (Figure 9b). Figure 10 shows the representative SEM images taken from the different times of CO2 bubbing. The sample a and sample b are composed of small ball-chain particles with 0.6−0.8 μm diameter. Then in sample c, the small sphere particles gather into spherical structures, and microcrystallines grow larger, becoming the major polymorph gradually; meanwhile the profile of flake-like structure appears. Sample d is practically spherical shape with a diameter ranging from 3 to 7 μm, but the conversion process from spherical vaterite to lamellate calcite is more obvious, and it can be seen that the spherical and lamellate morphologies combine together. Lastly, in sample e, the lamellate calcite with smooth surfaces increases remarkably. What’s more, there are two shapes of calcite. One is the spheroidal lamellate profile and the other is the regular cube, which may indicate that the former stems from the dissolution and recrystallization of vaterite CaCO3 and the latter is formed with ionic Ca2+ and CO32− through eq 7. The transformation from vaterite to calcite is widely known to proceed through the dissolution−recrystallization process, and it can be seen that the nucleation and the subsequent growth of the calcite crystals occur around part of a large spherical vaterite particle, suggesting a heterogeneous nucleation mechanism between

increasing the Asp concentration because it promotes eq 8. This result brings about generating more vaterite CaCO3 and less calcite CaCO3. However, the temperature has a complex effect on the CaCO3 polymorphs. The Transition State Theory points that chemical reactions must undergo a transition state called activated complex,28,29 which is the essence of activation energy, mainly affected by the property of reactants. Equation 7 more easily captures calcium than does eq 9, which leads to the activation energy Ea7 of eq 7 being lower than Ea9 of eq 9.30 According to the Arrhenius equation,31 the high temperature favors the reaction with high activation energy, while the low temperature is in favor of the reaction with low one. However, eq 9 is not only affected by the temperature, but also by the concentration of CaY2 in the solution. Figure 7 shows the variation of the conductivity of CaY2 solution after the temperature compensation versus the different temperature at pH 6 and pH 11, respectively. The curves reveal that the conductivity increases with the increasing temperature, meaning that the CaY2 tends to generation at low temperature. According to the above analysis, we believe that the concentration of CaY2 is the main factor in the high temperature period, which leads to not enough chelated calcium CaY2 to form vaterite, but more ionized calcium Ca2+ to calcite, so that eq 7 becomes the main reaction. Additionally, the temperature is the main factor in the low temperature period, which causes that the rate of eq 7 is faster than one of eq 9, so that eq 7 is still the main reaction, consistent to Figure 3. Moreover, we find the optimum temperature (40 °C) to generate vaterite between high and low temperature. Of note, the existence of amorphous calcium carbonate (ACC) at low temperature (10−20 °C) cannot be elaborated through eqs 3−9. It might be ascribed to decreasing the thermal vibration of ions because of low temperature. The CaCO3 particle precipitates via disorder accumulation, when reaching the supersaturation. And the thermal vibration does not have enough energy to recombine the ion distribution and change the crystal polymorph of CaCO3, resulting in a amount of ACC. 3.4. Changes in the Polymorph and Morphology of CaCO3 during Precipitation. The calcite CaCO3 could be obtained from both eq 7 and transformation of vaterite. To further investigate the mineralization mechanism of the spherical vaterite in the present of Asp and its transformation to calcite, we synthesized the particles under the conditions of initial pH (11), mole ratio of Asp to Ca(OH)2 (2:1), volume ratio of CO2 to N2 (40:160 mL/min). Figure 8 shows the change in the pH and conductivity of the CaY2 alkaline solution 733



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Figure 10. SEM images of precipitated CaCO3 at various elapsed times of CO2 gas bubbling. Inset: magnified SEM images.

the two crystalline phases.32,33 In this case, the spherical vaterite not only performs as an inorganic template but also provides Ca2+ and CO32− ions for recrystallization of calcite through dissolution of vaterite. Therefore, Asp can use the −COO− and −NH2 groups to interact with Ca2+ ion of CaCO3 crystals through chelation to prevent Ca2+ from being captured by CO32−, and the further crystal growth of vaterite changes the

aggregation states with some additives,12,34,35 which promotes the stability on the metastable vaterite and delays its transformation to the calcite. However, in the absence of additives, the crystal rapidly transforms from vaterite to calcite within 2−3 min and then forms the multidimensional morphology of calcite.36,37 734



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Figure 11. TG-DSC curves of precipitated CaCO3 (a) in the presence of Asp, (b) in the absence of Asp.

Figure 12. Schematic diagram of the formation process of vaterite.

obtained vaterite is regarded as an organic−inorganic composite with Asp. Finally, the formation mechanism of spherical vaterite can be summarized as the schematic diagram shown in Figure 12. There are three stages A, B, C, occurring in the formation of the spherical vaterite.40,41 In the stage A, when CO2 dissolves into the CaY2 alkaline solution at pH 11, the CO32− anion increases and unites the Ca2+ cation which is bound to Asp anion. In the stage B, when the concentration of CaCO3 reaches the saturation, an amorphous phase precipitates and forms primary particles, and turbidity ensues. Then, the primary particles aggregate to form the second ball-chain particles, the vaterite microspheres with a diameter of about 600−800 nm. In stage C, with the continuous CO2 bubbling, the primary particles on the surface of the second particles transform into vaterite with a diameter from 3 to 7 μm due to the presence of Asp and the spherical vaterite is formed. Concurrent with the precipitation of vaterite, the Asp desorbs from the growing face at pH 9.0− 9.5, which causes vaterite to transform spherical lamellate calcite as the template of vaterite via dissolution and recrystallization.

In general, the kinetic control is based predominantly on the modification of the activation energy barrier of nucleation, crystal growth, and phase transformation.38 In this case, crystallization usually proceeds by a sequential process, which could be explained by Ostwald’s step rule.39 The metastable vaterite phase is formed from amorphous precursors and gradually transforms into the thermodynamically stable aragonite or calcite polymorph. In our experiments, the Asp can play an important role in the formation of vaterite via being adsorbed on the specific crystal face, which decreases the surface energy or creates a barrier for the transformation from vaterite to calcite. The simultaneous TG-DSC analysis was conducted to reveal the adsorption on the particles, shown in Figure 11. Herein, there are two stages of weight loss in the thermogram curve (Figure 11a). The first weight loss with a total 5.2% occurs from 50 to 600 °C, which can be assigned to the combustion and decomposition of the Asp adsorbed on the product. The second weight loss should be attributed to the decomposition of CaCO3 in the temperature range of 650−820 °C, with a corresponding endothermic peak at 810 °C in the DSC curve. Meanwhile, there are two other weak peaks in the DSC curve. The endothermic peak centered around 100 °C should be attributed to the evaporation of the adsorbed water, and the exothermic peak at 480 °C implies that the polymorphic change of the precipitated CaCO3 from vaterite to calcite.27 As a contrast, we also detected the product sampled in the absence of Asp by TG-DSC (Figure 11b). A little weight loss of 1.3% from 50 to 600 °C can be attributed to the evaporation of water, rather than additives in the TG curve. There is not any exothermic peak around 500 °C in the DSC curve, indicating that CaCO3 does not change its polymorph and is still calcite. TG-DSC analysis demonstrates that the

4. CONCLUSION In conclusion, the spherical vaterite has been successfully synthesized by biomineralization in Ca(OH)2 alkaline solution with aspartic acid additive. We studied the polymorph composition of precipitated CaCO3 at different Asp concentrations and temperatures. Experiments show that Asp plays a crucial role in the formation of biological mineral vaterite, which has a good stability effect on vaterite CaCO3. We also detected the change of polymorph and morphology of precipitated CaCO3 with CO2 bubbling. Further mechanism investigation proposes the chelate effect between Asp and Ca2+. 735



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(23) Udrea, I.; Capat, C.; Olaru, E. A.; Isopescu, R.; Mihai, M.; Mateescu, C. D.; et al. Ind. Eng. Chem. Res. 2012, 51 (24), 8185−93. (24) Chuajiw, W.; Nakano, M.; Takatori, K.; Kojima, T.; Wakimoto, Y.; Fukushima, Y. J. Environ. Sci. 2013, 25 (12), 2507−15. (25) Chuajiw, W.; Takatori, K.; Igarashi, T.; Hara, H.; Fukushima, Y. J. Cryst. Growth 2014, 386, 119−27. (26) McAfee, L. J. Chem. Educ. 2000, 77 (9), 1122. (27) Lai, Y.; Chen, L.; Bao, W.; Ren, Y.; Gao, Y.; Yin, Y.; et al. Cryst. Growth Des. 2015, 15 (3), 1194−200. (28) Mökkönen, H.; Ikonen, T.; Ala-Nissila, T.; Jónsson, H. J. Chem. Phys. 2015, 142 (22), 224906. (29) Zhang, Y.; Stecher, T.; Cvitaš, M. T.; Althorpe, S. C. J. Phys. Chem. Lett. 2014, 5 (22), 3976−80. (30) Brecevic, L.; Kralj, D. Croatica Chem. Acta 2007, 80 (3−4), 467−484. (31) Sierra, C. Biogeochemistry 2012, 108 (1−3), 1−15. (32) Wang, X.; Kong, R.; Pan, X.; Xu, H.; Xia, D.; Shan, H.; et al. J. Phys. Chem. B 2009, 113 (26), 8975−82. (33) Liu, R.; Liu, F.; Zhao, S.; Su, Y.; Wang, D.; Shen, Q. CrystEngComm 2013, 15 (3), 509−15. (34) Liu, R.; Liu, F.; Su, Y.; Wang, D.; Shen, Q. Langmuir 2015, 31 (8), 2502−10. (35) Okhrimenko, D. V.; Nissenbaum, J.; Andersson, M. P.; Olsson, M. H. M.; Stipp, S. L. S. Langmuir 2013, 29 (35), 11062−73. (36) Shen, Q.; Wei, H.; Zhou, Y.; Huang, Y.; Yang, H.; Wang, D.; et al. J. Phys. Chem. B 2006, 110 (7), 2994−3000. (37) Garcia-Carmona, J.; Morales, J. G.; Clemente, R.R. J. Cryst. Growth 2003, 249 (3−4), 561−71. (38) Malkaj, P.; Dalas, E. Cryst. Growth Des. 2004, 4 (4), 721−3. (39) Yec, C. C.; Zeng, H. C. J. Mater. Chem. A 2014, 2 (14), 4843− 51. (40) Kim, Y. Y.; Schenk, A. S.; Ihli, J.; Kulak, A. N.; Hetherington, N. B. J.; Tang, C. C.; et al. Nat. Commun. 2014, 5, 4341. (41) Tomioka, T.; Fuji, M.; Takahashi, M.; Takai, C.; Utsuno, M. Cryst. Growth Des. 2012, 12 (2), 771−6.

This chelate compound CaY2 can induce the formation of vaterite, and then Asp is adsorbed on the surface of vaterite, preventing the transformation to calcite above pH 9.5. Moreover, it is found that calcite can be obtained not only from the precipitation of ionized calcium Ca2+, but also the transformation from vaterite due to the decrease of pH. What’s more, the preparation method of vaterite in the Ca(OH)2− CO2 reaction system could been extensively applied in industrial production, which would provide a new strategy for designing advanced materials with specific and excellent properties.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: +86-5482-2222. Fax: +865482-7068. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS J.L. thanks Prof. Ma and Dr. Kong for their assistance and guidance. Thanks are also given to National Engineering Research Center of Ultrafine Powder and ECUST for all equipment and analysis.

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REFERENCES

(1) Wang, Y. Y.; Yao, Q. Z.; Li, H.; Zhou, G. T.; Sheng, Y. M. Cryst. Growth Des. 2015, 15 (4), 1714−25. (2) Udrea, I.; Capat, C.; Olaru, E. A.; Isopescu, R.; Mihai, M.; Mateescu, C. D.; et al. Ind. Eng. Chem. Res. 2012, 51 (24), 8185−93. (3) Walsh, D.; Mann, S. Nature 1995, 377 (6547), 320−3. (4) Falini, G.; Fermani, S.; Vanzo, S.; Miletic, M.; Zaffino, G. Eur. J. Inorg. Chem. 2005, 2005 (1), 162−7. (5) Dickinson, S. R.; Henderson, G. E.; McGrath, K. M. J. Cryst. Growth 2002, 244 (3−4), 369−78. (6) Xu, A. W.; Antonietti, M.; Cölfen, H.; Fang, Y. P. Adv. Funct. Mater. 2006, 16 (7), 903−8. (7) Trushina, D. B.; Bukreeva, T. V.; Kovalchuk, M. V.; Antipina, M. N. Mater. Sci. Eng., C 2014, 45, 644−658. (8) Nehrke, G.; Van Cappellen, P. J. Cryst. Growth 2006, 287 (2), 528−30. (9) Demichelis, R.; Raiteri, P.; Gale, J. D.; Dovesi, R. CrystEngComm 2012, 14 (1), 44−7. (10) Tong, H.; Ma, W.; Wang, L.; Wan, P.; Hu, J.; Cao, L. Biomaterials 2004, 25 (17), 3923−9. (11) Manoli, F.; Dalas, E. J. Cryst. Growth 2001, 222 (1−2), 293−7. (12) Hood, M. A.; Landfester, K.; Muñoz-Espí, R. Cryst. Growth Des. 2014, 14 (3), 1077−85. (13) Guo, Y. M.; Wang, F. F.; Zhang, J.; Yang, L.; Shi, X. M.; Fang, Q. L.; et al. Res. Chem. Intermed. 2013, 39 (6), 2407−15. (14) Kitamura, M. J. Cryst. Growth 2002, 237−239, 2205−2214. (15) Han, Y. S.; Hadiko, G.; Fuji, M.; Takahashi, M. J. Eur. Ceram. Soc. 2006, 26 (4−5), 843−7. (16) Smeets, P. J. M.; Cho, K. R.; et al. Nat. Mater. 2005, 14 (4), 394−9. (17) Wei, H.; Shen, Q.; Zhao, Y.; Wang, D. J.; Xu, D. F. J. Cryst. Growth 2003, 250 (3−4), 516−24. (18) Xu, S.; Wu, P. CrystEngComm 2013, 15 (25), 5179−88. (19) Wehrmeister, U.; Soldati, A. L.; Jacob, D. E.; Häger, T.; Hofmeister, W. J. Raman Spectrosc. 2010, 41 (2), 193−201. (20) Loges, N.; Graf, K.; Nasdala, L.; Tremel, W. Langmuir 2006, 22 (7), 3073−80. (21) Han, Y. S.; Hadiko, G.; Fuji, M.; Takahashi, M. J. Cryst. Growth 2005, 276 (3−4), 541−8. (22) Andreassen, J. P.; Flaten, E. M.; Beck, R.; Lewis, A. E. Chem. Eng. Res. Des. 2010, 88 (9), 1163−8. 736


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