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The preparation of calcium carbonate with different morphologies under the effect of alkanolamide 6502
Colloids and Surfaces A 588 (2020) 124392
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Colloids and Surfaces A journal homepage: www.elsevier.com/locate/colsurfa
The preparation of calcium carbonate with different morphologies under the effect of alkanolamide 6502
T
Jun Wanga,b, Jingzhao Songa,b, Zhiyong Jia,b,d, Jie Liua,b, Xiaofu Guoa,b, Yingying Zhaoa,b,d,e,*, Junsheng Yuana,b,c,* a
School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin, 300130, China Hebei Collaborative Innovation Center of Modern Marine Chemical Technology, Tianjin, 300130, China c Quanzhou Normal University, Fujian, 362000, China d National-Local Joint Engineering Laboratory for Energy Conservation in Chemical Process Integration and Resources Utilization, Tianjin, 300130, China e Tianjin Key Laboratory of Chemical Process Safety, Tianjin, 300130, China b
G R A P H I C A L A B S T R A C T
A R T I C LE I N FO
A B S T R A C T
Keywords: Calcium carbonate Crystallization Alkanolamide 6502 Hydrophobic
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.
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Corresponding authors at: School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin, 300130, China. E-mail addresses: [email protected] (Y. Zhao), [email protected] (J. Yuan).
https://doi.org/10.1016/j.colsurfa.2019.124392 Received 21 October 2019; Received in revised form 20 December 2019; Accepted 23 December 2019 Available online 24 December 2019 0927-7757/ © 2019 Elsevier B.V. All rights reserved.
Colloids and Surfaces A 588 (2020) 124392
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1. Introduction
Table 1 Experimental condition table.
Calcium carbonate is one of the most abundant minerals on earth and is widely used in various industries [1,2]. Calcium carbonate exists in nature mainly in three forms: calcite, aragonite and vaterite. Calcite usually exists as a rhomboid cube, which is the most thermodynamically stable form [3] and is widely used in cement, metallurgy and other industries [4]. Aragonite usually exists in the form of needles and it is thermally stable at high temperatures [5], widely used as fillers for biomedical materials and new composite materials [6]. Vaterite is the most unstable form in thermodynamics [7]. It can slowly convert to calcite, so it is the least discovered in nature. However, it has the advantages of low specific gravity, high luminescence and high refractive index and is used as a filler for plastics and paper making [8]. As for the polymorphism of calcium carbonate, it has a direct impact on the internal structure and external morphology of crystals, and scholars all over the world have explored continuously. In the existing studies, different forms of calcium carbonate crystals can be obtained by adding different organic compounds. Amer et al. [9] found that acicular, spherical and cauliflower calcium carbonate could be obtained by complexing hydroxyl with calcium ions under the effect of vitamin D2. SevgiPolat [10] found that adding sodium laurate to the solution of calcium chloride and sodium carbonate helped to form vaterite, and the crystal shape changed from cubic shape to elliptic shape. Yang et al. [11] crystallized calcium carbonate in xanthan glue solution, proving that the presence of Mg2+ ions not only affects the morphology of calcium carbonate, but also affects the pleomorphism of calcium carbonate. In addition, in the process of biomineralization, different amino acids also have different effects on calcium carbonate [12]. The hydrophobicity of calcium carbonate is paid more and more attention. Wang [13] and Chen [14] et al. synthesized hydrophobic calcium carbonate by carbonizing dodecanoic acid as organic substrates. Han [15] et al. modified calcium carbonate by adding calcium stearate in situ during carbonization, and measured good hydrophobicity. Zhao [16] et al. modified calcium carbonate with hydrogen dihydrogen phosphate, which can significantly improve the mechanical properties of PVC. Recently, Chen and his group had made some progress in biocompatible organic solvents [17–19]. Alkanolamide 6502 is a non-ionic surfactant with good foaming properties, foaming stability, infiltration decontamination, hard water resistance and other functions. In this paper, the effect of alkanolamide 6502 on precipitated calcium carbonate was studied, including dosages of alkanolamide 6502, temperature and stirring rate. The products were studied by X-ray diffraction (XRD), SEM, FT-IR, laser particle size analyzer, optical contact angle tester and specific surface and porosity analyzer. It offers a useful, simple and reproducible approach to obtain vaterite microcrystals with high specific surface area, and low wettability.
(a) (b) (c) (d) (e) (f) (g) (h) (i)
Volume fraction of added alanolamide 6502 (vol.%)
Reaction temperature (℃)
Stirring rate (rpm)
0 0.2 2 6 10 2 2 2 2
25 25 25 25 25 50 80 50 50
500 500 500 500 500 500 500 200 800
into from the bottom through micro porous aeration tray for 30 min. After the reaction, vacuum pump was used to filter the material solution, and the obtained solids were put into anhydrous ethanol and treated by ultrasound for 10 min. Finally, the product was dried in an oven at 80 ℃ for 2 h to obtain calcium carbonate. Then XRD, SEM, FTIR, particle size, contact angle characterization and specific surface area tests were conducted. The experimental conditions for each group of experiments were shown in Table 1. 2.3. Characterization methods The surface morphology of solid was characterized and analyzed by field emission environmental scanning electron microscope (SEM, Quanta 450 FEG, Quanta, USA) at 20.00 kv, and the magnification was 1000–10,000 times. The crystal shape of solid was analyzed by X-ray diffractometer (Da Vinci type, Brucker AXS, Germany). The operating voltage was 40 kV, the operating current was 40 mA, the scanning step was 0.2°, and the scanning range was 5–90 °. The solid was analyzed using the nicolet 6700 model from thermo fairchild, USA, with wave Numbers ranging from 4000 cm-1 to 400 cm-1. Laser particle size analyzer (Mastersizer 2000, Marvin instruments LTD) was used to analyze the particle size of solids by dry method. The solid powder was pressed into the tablet at 10 MPa for 30 s, and the contact angle of the solid was analyzed with an Optical Contact Angle tester (DAS30, KRUSS, German). The specific surface area of the product was analyzed by specific surface and porosity analyzer (ASAP2020M + C, Micromeritics, USA). 3. Results and discussion 3.1. Effect of alkanolamide 6502 dosage The experiment temperature was controlled at 25 ℃ and the stirring rate was kept at 500 rpm. The calcium carbonate solids obtained under the condition of adding different amounts of alkanolamide 6502 was analyzed by XRD, and the results are shown in Fig. 1. Kontoyannis et al. [20] conducted semi-quantitative analysis of three crystal types by means of XRD pattern. Semi-quantitative analysis of calcite and vaterite in solid samples was carried out by using Eqs. (1) and (2), and the analysis results are shown in Fig. 2.
2. Methods 2.1. Materials Alanolamide 6502 (solid content≥81.9 %) was purchased from Guangzhou suixin chemical industrial co. LTD. Calcium chloride (> 97 %), Lauric acid diethanolamide (> 95 %) and Diethanolamine (> 99 %) was purchased from Tianjin kmart chemical technology co. LTD. Ammonia gas (99.9 %) and Carbon dioxide (99.9 %) was purchased from Tianjin vista technology development co. LTD.
I104 X C =7.691* C XV I110 V
(1) (2)
X C + XV = 1 I104 C
represents the diffraction intensity of calcite 104 In the formula, plane, I110 V represents the diffraction intensity of vaterite 110 plane, and X C and XV represent the percentage of calcite and vaterite respectively. According to the XRD pattern analysis in Fig. 1, when alkanolamide 6502 was not added, characteristic peaks of calcite were observed at 23°, 29.4°, 35.9°, 39.4°, 43.1°, 47.5° and 48.5°, corresponding to the crystal plane of calcite (012), (104), (110), (113), (202), (018) and
2.2. Experimental method A certain amount of alanolamide 6502 was added to 500 mL CaCl2 solution (0.57 mol/L), and stirred at a fixed speed for 10 min at the set temperature to make it evenly mixed. Then ammonia gas (60 mL/min) was injected from the top, and carbon dioxide (30 mL/min) was passed 2
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Fig. 4. Particle size distribution of products with different alanolamide 6502 dosages (a) 0, (b) 0.2 %, (c) 2 %, (d) 6 %, (e) 10 %.
Fig. 1. XRD pattern of products with different alanolamide 6502 dosages (a) 0, (b) 0.2 %, (c) 2 %, (d) 6 %, (e) 10 %.
Fig. 5. XRD pattern of products with different temperatures (c) 25 ℃, (f) 50 ℃, (g) 80 ℃.
(116). The products were pure calcite, and no diffraction peaks of vaterite were detected. When alkanolamide 6502 was added, not only the characteristic peak of calcite was observed, but also the characteristic peak of vaterite was observed at 20.9°, 24.9°, 27.1°, 32.8°, 43.9° and 50°, corresponding to the crystal plane of vaterite (004), (110), (112), (114), (300) and (118), and indicating that vaterite was obtained when
Fig. 2. Semi-quantitative analysis of products with different alanolamide 6502 dosages (a) 0, (b) 0.2 %, (c) 2 %, (d) 6 %, (e) 10 %.
Fig. 3. SEM images of products with different alanolamide 6502 dosages (a) 0, (b) 0.2 %, (c) 2 %, (d) 6 %, (e) 10 %. 3
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Fig. 6. Semi-quantitative analysis of products with different temperatures (c) 25 ℃, (f) 50 ℃, (g) 80 ℃.
Fig. 8. Particle size distribution of products with different temperatures (c) 25 ℃, (f) 50 ℃, (g) 80 ℃.
alkanolamide 6502 was added. In addition, with increasing of the dosage, the diffraction peak intensity of calcite was decreased and that of vaterite was raised. The semi-quantitative calculation results are shown in Fig. 2. When there was no alanolamide 6502, the product was calcite. After adding 0.2 % of alanolamide 6502, the conversion of vaterite to calcite was inhibited due to its interaction with calcium carbonate, and the content of calcite rapidly decreased to 39.4 %. There was no diffraction peak of aragonite detected in the XRD pattern, and the content of vaterite increased to 60.6 %. With the dosage of alanolamide 6502 was increased to 6 %, calcite content decreased to 10.9 % and vaterite increased to 89.1 %. However, the content of calcite and vaterite had no significant change with an alanolamide 6502 concentration of 10 %. SEM microscopic morphology of calcium carbonate are shown in Fig. 3. Fig. 3(a) shows the image of obtained calcite without adding additives, it is a diamond-shaped crystal with a smooth but defective surface. When 0.2 % alkanolamide 6502 was added, the amount of cubic calcite decreased sharply, and hollow calcium carbonate dominated in Fig. 3(b). Hadiko et al. synthesized hollow CaCO3 particles by using bubble as template. The formation of hollow calcium carbonate may be due to the attachment of vaterite microcrystals to the surface of CO2, forming a layer of material that envelops the bubbles with the help of organic matter [21]. This phenomenon did not appear in the products with the dosage of 2 %. Fig. 3(c) shows the complete spherical calcium carbonate with a smooth surface. However, when 6 % alkanolamide 6502 was added, in addition to spherical calcium carbonate, a large number of tiny crystals were attached to the external surface of the sphere in Fig. 3(d). Fig. 3(e) shows microspheres of a smaller size, which are formed by the aggregation of tiny fusiform crystals with the dosage of alanolamide 6502 was 10 %. Meanwhile, combined with Fig. 4, it can be seen that more dosage leads to smaller particle size distribution. When the additive volume fraction was 0 %, 0.2 %, 2 %, their particle size distribution was more uniform. Smaller crystals appeared when the additive volume fraction was 6 % and 10 %. This indicated that additives can inhibit crystal growth through interaction with calcium carbonate.
Fig. 9. XRD pattern of products with different stirring rates (f) 200 rpm, (h) 500 rpm, (i) 800 rpm.
Fig. 10. Semi-quantitative analysis of with different stirring rates (f) 200 rpm, (h) 500 rpm, (i) 800 rpm.
Fig. 7. SEM images of products with different temperatures (c) 25 ℃, (f) 50 ℃, (g) 80 ℃. 4
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Fig. 11. SEM images of products with different stirring rates (f) 200 rpm, (h) 500 rpm, (i) 800 rpm.
As seen from SEM images (Fig. 7), temperature had a significant effect on the morphology of calcium carbonate. At 25 ℃, the complete spherical vaterite was obtained. When the temperature rose to 50 ℃, the product was dandelion shaped vaterite composed of lamellar flakes with uniform size and good dispersion. It is similar to vaterite obtained by Chen [22] with double jet method at 30 ℃. The aggregates of various sizes and shapes were obtained with excessive temperature of 80 ℃. Fig. 8 shows the grain size distribution at different temperatures. The higher temperature caused larger crystals. This may be due to the decrease in the solubility of carbon dioxide and calcium hydroxide with the rising of temperature. Meanwhile, microbubbles become larger with the rising of temperature, leading to worse mixing and mass transfer effect [15]. 3.3. Effect of stirring rate Stirring rate will affect the flow field in the crystallizer, thus affecting the mass transfer process of crystallization. Therefore, appropriate stirring is beneficial to crystallization. The experiment was conducted under the condition of adding 2 % alkanolamide 6502 at 50 ℃. Figs. 9 and 10 show the XRD pattern and semi-quantitative analysis of the products, and there was no significant difference between the products under 200 rpm and 500 rpm. When the stirring rate rose to 800 rpm, the composition changed and the diffraction peaks of calcite completely disappeared. At this time, the product was pure vaterite. This indicated that high stirring rate is more favorable to the formation of vaterite. Sand et al. investigated the effect of slight shaking and severe shaking on the polymorphism of calcium carbonate. It was speculated that the structure of the solvent was disturbed in the violently stirred solution, and the dynamics of water-vaterite interaction changed, then the formation with calcite form was inhibited [23]. The products obtained under different stirring rates, such as at 200 rpm, 500 rpm and 800 rpm were analyzed by SEM (Fig. 11). The particle size distribution of products was shown in Fig. 12. The products obtained under the three conditions had no significant difference in general morphology and particle size distribution. In Fig. 11(h), the interstitial structures are more tightly bounded and have different degrees of adhesion. In Fig. 9(f), the crystals are more uniform, smooth, and layered. The lamellar structure in Fig. 9(i) is incomplete, and many fine crystals are observed. The particle size of the product is slightly larger when the stirring rate increased from 200 rpm to 500 rpm, which may be due to the fact that alkanolamide 6502 adhered to the crystal surface and inhibited the growth of the crystal under poor mixing conditions. However, more crystals with smaller size appeared at 800 rpm. This is because the collision between the blade and the crystal at a higher stirring rate, resulting in crystal breakage.
Fig. 12. Particle size distribution of products with different stirring rates (f) 200 rpm, (h) 500 rpm, (i) 800 rpm.
Fig. 13. FT-IR spectra of products.
3.2. Effect of temperature In the existing studies, temperature is also an important factor of the calcium carbonate crystallization process. Therefore, the effect of temperatures such as 25 ℃, 50 ℃ and 80 ℃ on the crystallization of calcium carbonate was investigated under the condition of stirring rate was 500 rpm and dosage of alkanolamide 6502 was 2 %. The XRD results are shown in Fig. 5. When the temperature rose from 25 ℃ to 50 ℃, the diffraction peak of calcite decreased and the diffraction peak of vaterite increased. Combined with the semi-quantitative analysis results in Fig. 6, it can be known that the content of vaterite rose from 79.8 % to 92.3 %. When the temperature further rose to 80 ℃, only the diffraction peak of vaterite was shown in the XRD pattern. Thus, it can be seen that high temperature is conducive to the production of vaterite.
3.4. Infrared spectrum analysis Fig. 13 shows the infrared spectra under different conditions. Infrared spectrogram also proves the appearance of two crystal types. Due to the difference in crystal types, the absorption peak positions of vaterite and calcite are also different in spectrogram. The absorption peak 5
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Fig. 14. Minimum (a) and maximum (g) contact angles.
intensities of CeH and eOH are getting higher and higher, which proves that the long chain of alanolamide 6502 adsorbs on the surface of calcium carbonate. 3.5. Contact angle analysis The hydrophilic property of calcium carbonate is one of the biggest problems that calcium carbonate is difficult to disperse in polymer matrix, making it difficult to be widely used. The surface modification of calcium carbonate by hydrophobic material will expand the application range of calcium carbonate, and the surface modification of surfactants has been studied [13]. In our study, the hydrophobic property of the products was also studied. Fig. 14 shows the minimum (a) and maximum (g) contact angles. Fig. 15 shows the contact angle of all the products. It can be seen that the contact angle of the sample is 19.5° without alkanolamide 6502, while the contact angle increased sharply to 110.3° when the dosage of alkanolamide 6502 was 0.2 %. Under other experimental conditions, the contact angle is above 120°. The results showed that alkanolamide 6502 affected the surface structure of precipitated calcium carbonate and made it hydrophobic.
Fig. 15. Contact Angle of products.
3.6. Mechanism analysis In the precipitation process of calcium carbonate, a recognized concern is the transformation of crystalline form. Recently, researchers had shown that the chemical component of amorphous calcium carbonate (ACC) is nominally CaCO3·H2O. Pure ACC (without additives) is converted to calcite by vaterite intermediates at low temperature (< 30 °C) and to aragonite via vaterite at high temperature (≥40 °C) [25,26]. And some researchers had confirmed that the conversion of vaterite to calcite is a solution-reprecipitation mechanism [27]. The addition of organics to the reactants affects the density, viscosity, surface tension, and permittivity of the solution. Surfactants reduce the surface tension of water and concentrate in solution. Organic additives in aqueous solutions affect the solubility of substrates and products, as well as the interactions between particles [28]. As for the influence of alcohols on the polymorphism of calcium carbonate, the main reason is that the hydroxyl group (eOH) is adsorbed on the surface of calcium carbonate, and alcohols (such as alkanolamide 6502) with molecular weight greater than methanol have stronger interaction with calcium carbonate crystal than water [29]. Fig. 16 shows the specific surface area of all products. The vaterite polymorph of calcium carbonate has higher porosity and specific surface area [30]. So, it is more conducive to alcohol adsorption. Alkanolamide 6502 contains hydroxyl groups. It can be simplified to ReOH, where R is the long chain group. When alkanolamide 6502 was not added, the precipitated calcium carbonate was completely converted to calcite via vaterite as the intermediate. When alkanolamide 6502 was added, the hydrophilic group hydroxyl of alkanolamide 6502 was adsorbed on the surface of
Fig. 16. Specific Surface Area of products.
of vaterite is at 1472 cm−1,1085 cm−1,875 cm−1,746 cm−1, while the absorption peak at 712 cm−1 is assigned to calcite [24]. Absorption peaks of vaterite were observed from Fig. 13(c) to (i), this suggested that vaterite was dominant. However, in Fig. 13(b), not only the characteristic peak of vaterite, but also the characteristic peak of calcite (709 cm−1) was observed. This indicated that both vaterite and calcite were dominant at this time. In Fig. 13(a), the characteristic peak at 709 cm−1 confirmed the presence of pure calcite. 2924 cm−1 and 2854 cm−1 are the absorption peaks of CeH anti-symmetric and symmetric stretching vibration, and 3452 cm−1 is the absorption peak of eOH stretching vibration [24]. It can be observed that spectrum (a) has no absorption peak at 2924 cm−1 and 2854 cm−1, and the absorption peak at 3452 cm−1 may be caused by eOH in water vapor. It can be seen from (a), (b), (c), (d) and (e) that the vibration absorption peaks 6
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Fig. 17. XRD pattern of Lauric acid diethanolamide (a) and Diethanolamine (b).
Declaration of Competing Interest
the intermediate vaterite. The hydrophobic group at the other end prevented the crystal nucleus from contacting with water. Hence it will inhibit the dissolution of vaterite, and lead to the hydrophobic properties of the crystal. In addition, alkanolamide 6502 can be adsorbed on the solid surface to prevent particle agglomeration [28]. In order to further investigate the crystallization mechanism of calcium carbonate with alkanolamide 6502, its two main components, diethanolamine lauric acid and diethanolamine, were used as additives. The experiment was conducted at 25 ℃ and 500 rpm, the same amount (3.2 mmol/L) of diethanolamine lauric acid and diethanolamine were added respectively. Fig. 17 showed the XRD patterns of products and the structural formula of diethanolamine lauric acid (a) and diethanolamine (b), respectively. The results showed that pure diethanolamine lauric acid would cause the crystal products to be vaterite, but the effect of pure diethanolamine was not obvious. This result supports the mechanism of hydroxyl adsorption. It is further suggested that the main factor inhibiting the dissolution-reprecipitation process of vaterite is diethanolamine lauric acid.
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements The work is supported by Science and technology project of Hebei Province (17273101D), Chinese Postdoctoral Science Foundation (2017M611142), National Key Research and Development Program (2016YFB0600500), National Natural Science Foundation of China (21306037), Program for Changjiang Scholars and Innovative Research Team in University (IRT14R14). References [1] G.J. Price, M.F. Mahon, J. Shannon, et al., Composition of calcium carbonate polymorphs precipitated using ultrasound, Cryst. Growth Des. 11 (1) (2011) 39–44. [2] Y. Liu, Y.J. Cui, H.Y. Mao, et al., Calcium carbonate crystallization in the presence of casein, Cryst. Growth Des. 12 (10) (2012) 4720–4726. [3] T. Kato, A. Sugawara, N. Hosoda, Calcium carbonate–organic hybrid materials, Adv. Mater. 14 (12) (2002) 869–877. [4] X. Yang, G. Xu, The influence of xanthan on the crystallization of calcium carbonate, J. Cryst. Growth 314 (1) (2011) 231–238. [5] R.M. Santos, P. Ceulemans, T.V. Gerven, Synthesis of pure aragonite by sonochemical mineral carbonation, Chem. Eng. Res. Des. 90 (6) (2012) 715–725. [6] S.I. Stupp, Molecular manipulation of microstructures: biomaterials, ceramics, and semiconductors, Science 277 (5330) (1997) 1242–1248. [7] A. Le Bail, S. Ouhenia, D. Chateigner, Microtwinning hypothesis for a more ordered vaterite model, Powder Diffr. 26 (01) (2011) 16–21. [8] A. Declet, E. Reyes, O.M. Suárez, Calcium carbonate precipitation: a review of the carbonate crystallization process and applications in bioinspired composites, Rev. Adv. Mater. Sci. 44 (1) (2016) 87–107. [9] A. Lydia, O. Salim, B. Imad, et al., The effect of ergocalciferol on the precipitation of calcium carbonate, J. Cryst. Growth 504 (2018) 49–59. [10] P. Sevgi, Evaluation of the effects of sodium laurate on calcium carbonate precipitation: characterization and optimization studies, J. Cryst. Growth 508 (2019) 8–18. [11] X. Yang, G. Xu, The influence of xanthan on the crystallization of calcium carbonate, J. Cryst. Growth 314 (1) (2011) 231–238. [12] Š Lara, K. Jasminka, N.D. Branka, M.-S. Nadica, P. Milivoj, Daniel M. Lyons, K. Damir, The effect of different amino acids on spontaneous precipitation of calcium carbonate polymorphs, J. Cryst. Growth 486 (2018) 71–81. [13] C. Wang, C. Piao, X. Zhai, et al., Synthesis and characterization of hydrophobic calcium carbonate particles via a dodecanoic acid inducing process, Powder Technol. 198 (1) (2010) 131–134. [14] Y. Chen, X. Ji, G. Zhao, et al., Facile preparation of cubic calcium carbonate nanoparticles with hydrophobic properties via a carbonation route, Powder Technol. 200 (3) (2010) 144–148. [15] C.L. Han, Y.P. Hu, K. Wang, G.S. Luo, Preparation and in-situ surface modification of CaCO3 nanoparticles with calcium stearate in a microreaction system, Powder Technol. 356 (2019) 414–422. [16] L. Zhao, Y. Zhang, Y. Miao, et al., Controlled synthesis, characterization and application of hydrophobic calcium carbonate nanoparticles in PVC, Powder Technol. 288 (2015) 184–190.
4. Conclusions In this work, the effect of alkanolamide 6502 on the crystal form and shape of precipitated calcium carbonate was studied. The factors of addition fraction of alkanolamide 6502, temperature and stirring rate all affect the formation of vaterite. The increase of the volume fraction of alkanolamide 6502 results in smaller particle size. But higher temperatures cause particles to clump together. At higher stirring rate, the crushing phenomenon is obvious and the particle size distribution is uneven. Moreover, different shapes of precipitated calcium carbonate were prepared, such as hollow spherical, spherical, layered dandelion shape, and so on. The presence of alkanolamide 6502 will also change the surface properties of precipitated calcium carbonate from hydrophilic to hydrophobic. Pure vaterite with high specific surface area and low wettability was prepared at a dosage of 2 % alanolamide, a temperature of 50 ℃ and a stirring rate of 800 rpm. The formation mechanism of vaterite was explained in view of the adsorption of hydroxyl group.
CRediT authorship contribution statement Jun Wang: Supervision. Jingzhao Song: Conceptualization, Data curation, Writing - original draft. Zhiyong Ji: Validation. Jie Liu: Formal analysis. Xiaofu Guo: Software. Yingying Zhao: Methodology, Investigation, Writing - review & editing, Visualization. Junsheng Yuan: Project administration, Resources. 7
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Colloids and Surfaces A journal homepage: www.elsevier.com/locate/colsurfa
The preparation of calcium carbonate with different morphologies under the effect of alkanolamide 6502
T
Jun Wanga,b, Jingzhao Songa,b, Zhiyong Jia,b,d, Jie Liua,b, Xiaofu Guoa,b, Yingying Zhaoa,b,d,e,*, Junsheng Yuana,b,c,* a
School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin, 300130, China Hebei Collaborative Innovation Center of Modern Marine Chemical Technology, Tianjin, 300130, China c Quanzhou Normal University, Fujian, 362000, China d National-Local Joint Engineering Laboratory for Energy Conservation in Chemical Process Integration and Resources Utilization, Tianjin, 300130, China e Tianjin Key Laboratory of Chemical Process Safety, Tianjin, 300130, China b
G R A P H I C A L A B S T R A C T
A R T I C LE I N FO
A B S T R A C T
Keywords: Calcium carbonate Crystallization Alkanolamide 6502 Hydrophobic
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.
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Corresponding authors at: School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin, 300130, China. E-mail addresses: [email protected] (Y. Zhao), [email protected] (J. Yuan).
https://doi.org/10.1016/j.colsurfa.2019.124392 Received 21 October 2019; Received in revised form 20 December 2019; Accepted 23 December 2019 Available online 24 December 2019 0927-7757/ © 2019 Elsevier B.V. All rights reserved.
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1. Introduction
Table 1 Experimental condition table.
Calcium carbonate is one of the most abundant minerals on earth and is widely used in various industries [1,2]. Calcium carbonate exists in nature mainly in three forms: calcite, aragonite and vaterite. Calcite usually exists as a rhomboid cube, which is the most thermodynamically stable form [3] and is widely used in cement, metallurgy and other industries [4]. Aragonite usually exists in the form of needles and it is thermally stable at high temperatures [5], widely used as fillers for biomedical materials and new composite materials [6]. Vaterite is the most unstable form in thermodynamics [7]. It can slowly convert to calcite, so it is the least discovered in nature. However, it has the advantages of low specific gravity, high luminescence and high refractive index and is used as a filler for plastics and paper making [8]. As for the polymorphism of calcium carbonate, it has a direct impact on the internal structure and external morphology of crystals, and scholars all over the world have explored continuously. In the existing studies, different forms of calcium carbonate crystals can be obtained by adding different organic compounds. Amer et al. [9] found that acicular, spherical and cauliflower calcium carbonate could be obtained by complexing hydroxyl with calcium ions under the effect of vitamin D2. SevgiPolat [10] found that adding sodium laurate to the solution of calcium chloride and sodium carbonate helped to form vaterite, and the crystal shape changed from cubic shape to elliptic shape. Yang et al. [11] crystallized calcium carbonate in xanthan glue solution, proving that the presence of Mg2+ ions not only affects the morphology of calcium carbonate, but also affects the pleomorphism of calcium carbonate. In addition, in the process of biomineralization, different amino acids also have different effects on calcium carbonate [12]. The hydrophobicity of calcium carbonate is paid more and more attention. Wang [13] and Chen [14] et al. synthesized hydrophobic calcium carbonate by carbonizing dodecanoic acid as organic substrates. Han [15] et al. modified calcium carbonate by adding calcium stearate in situ during carbonization, and measured good hydrophobicity. Zhao [16] et al. modified calcium carbonate with hydrogen dihydrogen phosphate, which can significantly improve the mechanical properties of PVC. Recently, Chen and his group had made some progress in biocompatible organic solvents [17–19]. Alkanolamide 6502 is a non-ionic surfactant with good foaming properties, foaming stability, infiltration decontamination, hard water resistance and other functions. In this paper, the effect of alkanolamide 6502 on precipitated calcium carbonate was studied, including dosages of alkanolamide 6502, temperature and stirring rate. The products were studied by X-ray diffraction (XRD), SEM, FT-IR, laser particle size analyzer, optical contact angle tester and specific surface and porosity analyzer. It offers a useful, simple and reproducible approach to obtain vaterite microcrystals with high specific surface area, and low wettability.
(a) (b) (c) (d) (e) (f) (g) (h) (i)
Volume fraction of added alanolamide 6502 (vol.%)
Reaction temperature (℃)
Stirring rate (rpm)
0 0.2 2 6 10 2 2 2 2
25 25 25 25 25 50 80 50 50
500 500 500 500 500 500 500 200 800
into from the bottom through micro porous aeration tray for 30 min. After the reaction, vacuum pump was used to filter the material solution, and the obtained solids were put into anhydrous ethanol and treated by ultrasound for 10 min. Finally, the product was dried in an oven at 80 ℃ for 2 h to obtain calcium carbonate. Then XRD, SEM, FTIR, particle size, contact angle characterization and specific surface area tests were conducted. The experimental conditions for each group of experiments were shown in Table 1. 2.3. Characterization methods The surface morphology of solid was characterized and analyzed by field emission environmental scanning electron microscope (SEM, Quanta 450 FEG, Quanta, USA) at 20.00 kv, and the magnification was 1000–10,000 times. The crystal shape of solid was analyzed by X-ray diffractometer (Da Vinci type, Brucker AXS, Germany). The operating voltage was 40 kV, the operating current was 40 mA, the scanning step was 0.2°, and the scanning range was 5–90 °. The solid was analyzed using the nicolet 6700 model from thermo fairchild, USA, with wave Numbers ranging from 4000 cm-1 to 400 cm-1. Laser particle size analyzer (Mastersizer 2000, Marvin instruments LTD) was used to analyze the particle size of solids by dry method. The solid powder was pressed into the tablet at 10 MPa for 30 s, and the contact angle of the solid was analyzed with an Optical Contact Angle tester (DAS30, KRUSS, German). The specific surface area of the product was analyzed by specific surface and porosity analyzer (ASAP2020M + C, Micromeritics, USA). 3. Results and discussion 3.1. Effect of alkanolamide 6502 dosage The experiment temperature was controlled at 25 ℃ and the stirring rate was kept at 500 rpm. The calcium carbonate solids obtained under the condition of adding different amounts of alkanolamide 6502 was analyzed by XRD, and the results are shown in Fig. 1. Kontoyannis et al. [20] conducted semi-quantitative analysis of three crystal types by means of XRD pattern. Semi-quantitative analysis of calcite and vaterite in solid samples was carried out by using Eqs. (1) and (2), and the analysis results are shown in Fig. 2.
2. Methods 2.1. Materials Alanolamide 6502 (solid content≥81.9 %) was purchased from Guangzhou suixin chemical industrial co. LTD. Calcium chloride (> 97 %), Lauric acid diethanolamide (> 95 %) and Diethanolamine (> 99 %) was purchased from Tianjin kmart chemical technology co. LTD. Ammonia gas (99.9 %) and Carbon dioxide (99.9 %) was purchased from Tianjin vista technology development co. LTD.
I104 X C =7.691* C XV I110 V
(1) (2)
X C + XV = 1 I104 C
represents the diffraction intensity of calcite 104 In the formula, plane, I110 V represents the diffraction intensity of vaterite 110 plane, and X C and XV represent the percentage of calcite and vaterite respectively. According to the XRD pattern analysis in Fig. 1, when alkanolamide 6502 was not added, characteristic peaks of calcite were observed at 23°, 29.4°, 35.9°, 39.4°, 43.1°, 47.5° and 48.5°, corresponding to the crystal plane of calcite (012), (104), (110), (113), (202), (018) and
2.2. Experimental method A certain amount of alanolamide 6502 was added to 500 mL CaCl2 solution (0.57 mol/L), and stirred at a fixed speed for 10 min at the set temperature to make it evenly mixed. Then ammonia gas (60 mL/min) was injected from the top, and carbon dioxide (30 mL/min) was passed 2
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Fig. 4. Particle size distribution of products with different alanolamide 6502 dosages (a) 0, (b) 0.2 %, (c) 2 %, (d) 6 %, (e) 10 %.
Fig. 1. XRD pattern of products with different alanolamide 6502 dosages (a) 0, (b) 0.2 %, (c) 2 %, (d) 6 %, (e) 10 %.
Fig. 5. XRD pattern of products with different temperatures (c) 25 ℃, (f) 50 ℃, (g) 80 ℃.
(116). The products were pure calcite, and no diffraction peaks of vaterite were detected. When alkanolamide 6502 was added, not only the characteristic peak of calcite was observed, but also the characteristic peak of vaterite was observed at 20.9°, 24.9°, 27.1°, 32.8°, 43.9° and 50°, corresponding to the crystal plane of vaterite (004), (110), (112), (114), (300) and (118), and indicating that vaterite was obtained when
Fig. 2. Semi-quantitative analysis of products with different alanolamide 6502 dosages (a) 0, (b) 0.2 %, (c) 2 %, (d) 6 %, (e) 10 %.
Fig. 3. SEM images of products with different alanolamide 6502 dosages (a) 0, (b) 0.2 %, (c) 2 %, (d) 6 %, (e) 10 %. 3
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Fig. 6. Semi-quantitative analysis of products with different temperatures (c) 25 ℃, (f) 50 ℃, (g) 80 ℃.
Fig. 8. Particle size distribution of products with different temperatures (c) 25 ℃, (f) 50 ℃, (g) 80 ℃.
alkanolamide 6502 was added. In addition, with increasing of the dosage, the diffraction peak intensity of calcite was decreased and that of vaterite was raised. The semi-quantitative calculation results are shown in Fig. 2. When there was no alanolamide 6502, the product was calcite. After adding 0.2 % of alanolamide 6502, the conversion of vaterite to calcite was inhibited due to its interaction with calcium carbonate, and the content of calcite rapidly decreased to 39.4 %. There was no diffraction peak of aragonite detected in the XRD pattern, and the content of vaterite increased to 60.6 %. With the dosage of alanolamide 6502 was increased to 6 %, calcite content decreased to 10.9 % and vaterite increased to 89.1 %. However, the content of calcite and vaterite had no significant change with an alanolamide 6502 concentration of 10 %. SEM microscopic morphology of calcium carbonate are shown in Fig. 3. Fig. 3(a) shows the image of obtained calcite without adding additives, it is a diamond-shaped crystal with a smooth but defective surface. When 0.2 % alkanolamide 6502 was added, the amount of cubic calcite decreased sharply, and hollow calcium carbonate dominated in Fig. 3(b). Hadiko et al. synthesized hollow CaCO3 particles by using bubble as template. The formation of hollow calcium carbonate may be due to the attachment of vaterite microcrystals to the surface of CO2, forming a layer of material that envelops the bubbles with the help of organic matter [21]. This phenomenon did not appear in the products with the dosage of 2 %. Fig. 3(c) shows the complete spherical calcium carbonate with a smooth surface. However, when 6 % alkanolamide 6502 was added, in addition to spherical calcium carbonate, a large number of tiny crystals were attached to the external surface of the sphere in Fig. 3(d). Fig. 3(e) shows microspheres of a smaller size, which are formed by the aggregation of tiny fusiform crystals with the dosage of alanolamide 6502 was 10 %. Meanwhile, combined with Fig. 4, it can be seen that more dosage leads to smaller particle size distribution. When the additive volume fraction was 0 %, 0.2 %, 2 %, their particle size distribution was more uniform. Smaller crystals appeared when the additive volume fraction was 6 % and 10 %. This indicated that additives can inhibit crystal growth through interaction with calcium carbonate.
Fig. 9. XRD pattern of products with different stirring rates (f) 200 rpm, (h) 500 rpm, (i) 800 rpm.
Fig. 10. Semi-quantitative analysis of with different stirring rates (f) 200 rpm, (h) 500 rpm, (i) 800 rpm.
Fig. 7. SEM images of products with different temperatures (c) 25 ℃, (f) 50 ℃, (g) 80 ℃. 4
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Fig. 11. SEM images of products with different stirring rates (f) 200 rpm, (h) 500 rpm, (i) 800 rpm.
As seen from SEM images (Fig. 7), temperature had a significant effect on the morphology of calcium carbonate. At 25 ℃, the complete spherical vaterite was obtained. When the temperature rose to 50 ℃, the product was dandelion shaped vaterite composed of lamellar flakes with uniform size and good dispersion. It is similar to vaterite obtained by Chen [22] with double jet method at 30 ℃. The aggregates of various sizes and shapes were obtained with excessive temperature of 80 ℃. Fig. 8 shows the grain size distribution at different temperatures. The higher temperature caused larger crystals. This may be due to the decrease in the solubility of carbon dioxide and calcium hydroxide with the rising of temperature. Meanwhile, microbubbles become larger with the rising of temperature, leading to worse mixing and mass transfer effect [15]. 3.3. Effect of stirring rate Stirring rate will affect the flow field in the crystallizer, thus affecting the mass transfer process of crystallization. Therefore, appropriate stirring is beneficial to crystallization. The experiment was conducted under the condition of adding 2 % alkanolamide 6502 at 50 ℃. Figs. 9 and 10 show the XRD pattern and semi-quantitative analysis of the products, and there was no significant difference between the products under 200 rpm and 500 rpm. When the stirring rate rose to 800 rpm, the composition changed and the diffraction peaks of calcite completely disappeared. At this time, the product was pure vaterite. This indicated that high stirring rate is more favorable to the formation of vaterite. Sand et al. investigated the effect of slight shaking and severe shaking on the polymorphism of calcium carbonate. It was speculated that the structure of the solvent was disturbed in the violently stirred solution, and the dynamics of water-vaterite interaction changed, then the formation with calcite form was inhibited [23]. The products obtained under different stirring rates, such as at 200 rpm, 500 rpm and 800 rpm were analyzed by SEM (Fig. 11). The particle size distribution of products was shown in Fig. 12. The products obtained under the three conditions had no significant difference in general morphology and particle size distribution. In Fig. 11(h), the interstitial structures are more tightly bounded and have different degrees of adhesion. In Fig. 9(f), the crystals are more uniform, smooth, and layered. The lamellar structure in Fig. 9(i) is incomplete, and many fine crystals are observed. The particle size of the product is slightly larger when the stirring rate increased from 200 rpm to 500 rpm, which may be due to the fact that alkanolamide 6502 adhered to the crystal surface and inhibited the growth of the crystal under poor mixing conditions. However, more crystals with smaller size appeared at 800 rpm. This is because the collision between the blade and the crystal at a higher stirring rate, resulting in crystal breakage.
Fig. 12. Particle size distribution of products with different stirring rates (f) 200 rpm, (h) 500 rpm, (i) 800 rpm.
Fig. 13. FT-IR spectra of products.
3.2. Effect of temperature In the existing studies, temperature is also an important factor of the calcium carbonate crystallization process. Therefore, the effect of temperatures such as 25 ℃, 50 ℃ and 80 ℃ on the crystallization of calcium carbonate was investigated under the condition of stirring rate was 500 rpm and dosage of alkanolamide 6502 was 2 %. The XRD results are shown in Fig. 5. When the temperature rose from 25 ℃ to 50 ℃, the diffraction peak of calcite decreased and the diffraction peak of vaterite increased. Combined with the semi-quantitative analysis results in Fig. 6, it can be known that the content of vaterite rose from 79.8 % to 92.3 %. When the temperature further rose to 80 ℃, only the diffraction peak of vaterite was shown in the XRD pattern. Thus, it can be seen that high temperature is conducive to the production of vaterite.
3.4. Infrared spectrum analysis Fig. 13 shows the infrared spectra under different conditions. Infrared spectrogram also proves the appearance of two crystal types. Due to the difference in crystal types, the absorption peak positions of vaterite and calcite are also different in spectrogram. The absorption peak 5
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Fig. 14. Minimum (a) and maximum (g) contact angles.
intensities of CeH and eOH are getting higher and higher, which proves that the long chain of alanolamide 6502 adsorbs on the surface of calcium carbonate. 3.5. Contact angle analysis The hydrophilic property of calcium carbonate is one of the biggest problems that calcium carbonate is difficult to disperse in polymer matrix, making it difficult to be widely used. The surface modification of calcium carbonate by hydrophobic material will expand the application range of calcium carbonate, and the surface modification of surfactants has been studied [13]. In our study, the hydrophobic property of the products was also studied. Fig. 14 shows the minimum (a) and maximum (g) contact angles. Fig. 15 shows the contact angle of all the products. It can be seen that the contact angle of the sample is 19.5° without alkanolamide 6502, while the contact angle increased sharply to 110.3° when the dosage of alkanolamide 6502 was 0.2 %. Under other experimental conditions, the contact angle is above 120°. The results showed that alkanolamide 6502 affected the surface structure of precipitated calcium carbonate and made it hydrophobic.
Fig. 15. Contact Angle of products.
3.6. Mechanism analysis In the precipitation process of calcium carbonate, a recognized concern is the transformation of crystalline form. Recently, researchers had shown that the chemical component of amorphous calcium carbonate (ACC) is nominally CaCO3·H2O. Pure ACC (without additives) is converted to calcite by vaterite intermediates at low temperature (< 30 °C) and to aragonite via vaterite at high temperature (≥40 °C) [25,26]. And some researchers had confirmed that the conversion of vaterite to calcite is a solution-reprecipitation mechanism [27]. The addition of organics to the reactants affects the density, viscosity, surface tension, and permittivity of the solution. Surfactants reduce the surface tension of water and concentrate in solution. Organic additives in aqueous solutions affect the solubility of substrates and products, as well as the interactions between particles [28]. As for the influence of alcohols on the polymorphism of calcium carbonate, the main reason is that the hydroxyl group (eOH) is adsorbed on the surface of calcium carbonate, and alcohols (such as alkanolamide 6502) with molecular weight greater than methanol have stronger interaction with calcium carbonate crystal than water [29]. Fig. 16 shows the specific surface area of all products. The vaterite polymorph of calcium carbonate has higher porosity and specific surface area [30]. So, it is more conducive to alcohol adsorption. Alkanolamide 6502 contains hydroxyl groups. It can be simplified to ReOH, where R is the long chain group. When alkanolamide 6502 was not added, the precipitated calcium carbonate was completely converted to calcite via vaterite as the intermediate. When alkanolamide 6502 was added, the hydrophilic group hydroxyl of alkanolamide 6502 was adsorbed on the surface of
Fig. 16. Specific Surface Area of products.
of vaterite is at 1472 cm−1,1085 cm−1,875 cm−1,746 cm−1, while the absorption peak at 712 cm−1 is assigned to calcite [24]. Absorption peaks of vaterite were observed from Fig. 13(c) to (i), this suggested that vaterite was dominant. However, in Fig. 13(b), not only the characteristic peak of vaterite, but also the characteristic peak of calcite (709 cm−1) was observed. This indicated that both vaterite and calcite were dominant at this time. In Fig. 13(a), the characteristic peak at 709 cm−1 confirmed the presence of pure calcite. 2924 cm−1 and 2854 cm−1 are the absorption peaks of CeH anti-symmetric and symmetric stretching vibration, and 3452 cm−1 is the absorption peak of eOH stretching vibration [24]. It can be observed that spectrum (a) has no absorption peak at 2924 cm−1 and 2854 cm−1, and the absorption peak at 3452 cm−1 may be caused by eOH in water vapor. It can be seen from (a), (b), (c), (d) and (e) that the vibration absorption peaks 6
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Fig. 17. XRD pattern of Lauric acid diethanolamide (a) and Diethanolamine (b).
Declaration of Competing Interest
the intermediate vaterite. The hydrophobic group at the other end prevented the crystal nucleus from contacting with water. Hence it will inhibit the dissolution of vaterite, and lead to the hydrophobic properties of the crystal. In addition, alkanolamide 6502 can be adsorbed on the solid surface to prevent particle agglomeration [28]. In order to further investigate the crystallization mechanism of calcium carbonate with alkanolamide 6502, its two main components, diethanolamine lauric acid and diethanolamine, were used as additives. The experiment was conducted at 25 ℃ and 500 rpm, the same amount (3.2 mmol/L) of diethanolamine lauric acid and diethanolamine were added respectively. Fig. 17 showed the XRD patterns of products and the structural formula of diethanolamine lauric acid (a) and diethanolamine (b), respectively. The results showed that pure diethanolamine lauric acid would cause the crystal products to be vaterite, but the effect of pure diethanolamine was not obvious. This result supports the mechanism of hydroxyl adsorption. It is further suggested that the main factor inhibiting the dissolution-reprecipitation process of vaterite is diethanolamine lauric acid.
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements The work is supported by Science and technology project of Hebei Province (17273101D), Chinese Postdoctoral Science Foundation (2017M611142), National Key Research and Development Program (2016YFB0600500), National Natural Science Foundation of China (21306037), Program for Changjiang Scholars and Innovative Research Team in University (IRT14R14). References [1] G.J. Price, M.F. Mahon, J. Shannon, et al., Composition of calcium carbonate polymorphs precipitated using ultrasound, Cryst. Growth Des. 11 (1) (2011) 39–44. [2] Y. Liu, Y.J. Cui, H.Y. Mao, et al., Calcium carbonate crystallization in the presence of casein, Cryst. Growth Des. 12 (10) (2012) 4720–4726. [3] T. Kato, A. Sugawara, N. Hosoda, Calcium carbonate–organic hybrid materials, Adv. Mater. 14 (12) (2002) 869–877. [4] X. Yang, G. Xu, The influence of xanthan on the crystallization of calcium carbonate, J. Cryst. Growth 314 (1) (2011) 231–238. [5] R.M. Santos, P. Ceulemans, T.V. Gerven, Synthesis of pure aragonite by sonochemical mineral carbonation, Chem. Eng. Res. Des. 90 (6) (2012) 715–725. [6] S.I. Stupp, Molecular manipulation of microstructures: biomaterials, ceramics, and semiconductors, Science 277 (5330) (1997) 1242–1248. [7] A. Le Bail, S. Ouhenia, D. Chateigner, Microtwinning hypothesis for a more ordered vaterite model, Powder Diffr. 26 (01) (2011) 16–21. [8] A. Declet, E. Reyes, O.M. Suárez, Calcium carbonate precipitation: a review of the carbonate crystallization process and applications in bioinspired composites, Rev. Adv. Mater. Sci. 44 (1) (2016) 87–107. [9] A. Lydia, O. Salim, B. Imad, et al., The effect of ergocalciferol on the precipitation of calcium carbonate, J. Cryst. Growth 504 (2018) 49–59. [10] P. Sevgi, Evaluation of the effects of sodium laurate on calcium carbonate precipitation: characterization and optimization studies, J. Cryst. Growth 508 (2019) 8–18. [11] X. Yang, G. Xu, The influence of xanthan on the crystallization of calcium carbonate, J. Cryst. Growth 314 (1) (2011) 231–238. [12] Š Lara, K. Jasminka, N.D. Branka, M.-S. Nadica, P. Milivoj, Daniel M. Lyons, K. Damir, The effect of different amino acids on spontaneous precipitation of calcium carbonate polymorphs, J. Cryst. Growth 486 (2018) 71–81. [13] C. Wang, C. Piao, X. Zhai, et al., Synthesis and characterization of hydrophobic calcium carbonate particles via a dodecanoic acid inducing process, Powder Technol. 198 (1) (2010) 131–134. [14] Y. Chen, X. Ji, G. Zhao, et al., Facile preparation of cubic calcium carbonate nanoparticles with hydrophobic properties via a carbonation route, Powder Technol. 200 (3) (2010) 144–148. [15] C.L. Han, Y.P. Hu, K. Wang, G.S. Luo, Preparation and in-situ surface modification of CaCO3 nanoparticles with calcium stearate in a microreaction system, Powder Technol. 356 (2019) 414–422. [16] L. Zhao, Y. Zhang, Y. Miao, et al., Controlled synthesis, characterization and application of hydrophobic calcium carbonate nanoparticles in PVC, Powder Technol. 288 (2015) 184–190.
4. Conclusions In this work, the effect of alkanolamide 6502 on the crystal form and shape of precipitated calcium carbonate was studied. The factors of addition fraction of alkanolamide 6502, temperature and stirring rate all affect the formation of vaterite. The increase of the volume fraction of alkanolamide 6502 results in smaller particle size. But higher temperatures cause particles to clump together. At higher stirring rate, the crushing phenomenon is obvious and the particle size distribution is uneven. Moreover, different shapes of precipitated calcium carbonate were prepared, such as hollow spherical, spherical, layered dandelion shape, and so on. The presence of alkanolamide 6502 will also change the surface properties of precipitated calcium carbonate from hydrophilic to hydrophobic. Pure vaterite with high specific surface area and low wettability was prepared at a dosage of 2 % alanolamide, a temperature of 50 ℃ and a stirring rate of 800 rpm. The formation mechanism of vaterite was explained in view of the adsorption of hydroxyl group.
CRediT authorship contribution statement Jun Wang: Supervision. Jingzhao Song: Conceptualization, Data curation, Writing - original draft. Zhiyong Ji: Validation. Jie Liu: Formal analysis. Xiaofu Guo: Software. Yingying Zhao: Methodology, Investigation, Writing - review & editing, Visualization. Junsheng Yuan: Project administration, Resources. 7
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