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A novel aqueous-phase route to synthesize hydrophobic CaCO3 particles in situ
Materials Science and Engineering C 27 (2007) 42 – 45 www.elsevier.com/locate/msec
A novel aqueous-phase route to synthesize hydrophobic CaCO3 particles in situ Chengyu Wang, Ye Sheng, Hari-Bala, Xu Zhao, Jingzhe Zhao, Xiaokun Ma, Zichen Wang ⁎ Institute of Chemistry, Jilin University, Changchun 130023, China Received 22 November 2005; received in revised form 20 December 2005; accepted 12 January 2006 Available online 28 February 2006
Abstract Hydrophobic CaCO3 particles were prepared in situ by carbonation of Ca(OH)2 slurry in the presence of the ethanol solution of oleic acid by mimicking the process of biomineralization. The weight ratio of oleic acid to CaCO3 changed from 0.3 to 3 wt.%. By changing the weight ratio of oleic acid to CaCO3, the surface property of CaCO3 particles was changed from hydrophilic to hydrophobic. Floating test and contact angle analysis of the obtained product indicated that the final CaCO3 obtained was hydrophobic. From the floating test, the active ratio of the modified CaCO3 might reach 100%. The contact angle of the modified CaCO3 was 108.77. IR spectrums of the CaCO3 particles showed the appearance of the alkyl groups from the oleic acid. We have succeeded in surface modification of CaCO3 with the hydrophobic oleic acid. © 2006 Elsevier B.V. All rights reserved. Keywords: Calcium carbonate; Hydrophobic; Oleic acid; Carbonation; Organic substrate
1. Introduction CaCO3 is one of the important fillers used in the industries of plastics, rubber, paint, and so on. One of the most problematic issues for the use of CaCO3 is the hydrophilic property, and this problem makes it very difficult to be used widely. Surface modification of CaCO3 with hydrophobic species would lead to a great expansion in its applications; since mineral particles are hardly dispersed in a polymer matrix [1]. The modification of the surface by surfactants has been extensively studied. For example, the surfactants containing reactive functional groups such as silane coupling agents [2,3], titanate coupling agents [4], or stearic acid [5] can all improve the hydrophobic properties of CaCO3. However, all the processes were conducted with the resultant CaCO3 products rather than during the synthesis process of CaCO3. Recently, the synthesis of organic–inorganic hybrids by mimicking biomineralization has attracted great attention [6]. Crystallization of CaCO3 in the presence of various additives and synthetic polymers has been investigated as a model of biomineralization [7–9]. It has been known that organic additives introduced to the crystallization ⁎ Corresponding author. E-mail address: [email protected] (Z. Wang). 0928-4931/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.msec.2006.01.003
process of CaCO3 modify the shapes of crystals [10,11] and control the nucleation and growth of particles, but there were still no the reports that the organic additives change the property of inorganic mineral in situ. In this paper, we paid our attention to the study of modification in situ by mimicking the process of biomineralization. Synthesis of CaCO3 was followed by two basic synthetic routes: (1) the solution route [12,13], through a double decomposition reaction, wherein aqueous CaCl2 and NaCO3, or CaCl2 and (NH4)2CO3, or Ca(NO3)2 and NaCO3 are combined in an equal molar ratio; and (2) the carbonation method [14], in which CO2 gas is bubbled through an aqueous slurry of Ca(OH)2. The latter is preferred in terms of environment preservation and the effective use of mineral resources. The carbonation method is an industrially useful method, but it is difficult to control the crystal shape and modification of CaCO3 [15]. Here, hydrophobic CaCO3 particles were synthesized in situ in aqueous solution by carbonation method. The oleic acid used as organic additive not only controls the nucleation and growth of CaCO3 but also modify the surface of CaCO3. Although many studies have shown that a lot of additives can influence the shape of crystals under laboratory conditions, the oleic acid has not been used for the crystallization of CaCO3. Meanwhile, the presence of CjC
C. Wang et al. / Materials Science and Engineering C 27 (2007) 42–45
43
Fig. 1. TEM of CaCO3 products obtained (a) in the absence of the solution of oleic acid, (b) in the presence of the solution of oleic acid.
All of the chemical reagents used in this experiment were of analytical grade. The procedure employed for the synthesis of CaCO3 was as follows. 10 g of CaO was digested in 100 ml of 80 °C distilled water to form Ca(OH)2 slurry. After a day, the slurry was filtered through a 200 mesh sieve in order to remove the impurity and large particles and then transferred into a 250 ml three-necked flask. After addition of the ethanol solution of oleic acid (0.1 M) into the flask, the mixture was stirred vigorously for 2 h at room temperature using a mechanical stirrer in order to ensure that the COO− of oleic acid could react with Ca2+. Then CO2 gas was introduced into the mixture through a tube while the mixture was stirred at the same time. The reaction was performed at ambient reaction condition and controlled by the pH of the medium. The reaction was stopped when the final pH value of suspension reached about 7. The precipitates were separated from the mother liquid by filtration and rinsed three times with absolute ethanol to remove remaining oleic acid. The final product was dried for 1day in an oven at 100 °C. The morphology and particle size of the products were characterized by virtue of transmission electron micrograph (TEM). TEM measurement was carried out on a Hitachi 8100 IV at 100kV. The crystalline phase of the synthesized CaCO3 was characterized by X-ray diffraction (XRD) analysis with a Shimadju D/max-rA X-ray diffractometer with Cu Ka radiation (λ = 0.15418 nm), accelerating voltage being 40 kV, current 30 mA, and scanning rate 4 °/min. In order to study the surface characteristic, Fourier transform infrared spectroscopy (RT-IR) was recorded on an Ominic system 2000 with the KBr pellet method.
3. Results and discussion From Fig. 1a we could see that the spindle-like CaCO3 with the diameter of about 100nm (the ratio of diameter to length
a
b
2920 2853
2. Experimental
The effect of surface modification was evaluated by the relative contact angle and active ratio. The contact angle was measured at 25 °C with a FTÅ200 (USA) contact angle analyzer. On flat solid surfaces, the contact angle can be measured by the sessile drop technique. The powdery samples (1g) in 10MPa pressure were first pressed into thin pellet and then the water droplet was dropped onto the pellet. The contact angle against water on a horizontal surface of a pellet was obtained. The effect of surface modification was evaluated by the floating test [16]. 10 g of the final sample was put into 100ml of water. We measured the ratio of floated product to overall weight of sample after they was mixed in water and stirred vigorously. This ratio was called the active ratio. The higher the active ratio, the better the hydrophobic property was.
Transmittance
bonds of oleic acid makes the final products easily react with polymer matrix. Using this method, it is easy to synthesize hydrophobic CaCO3 particles in the presence of oleic acid at ambient reaction conditions and is potentially important for industrial process of biomineralization.
3500
3000
2500
2000
1500
1000
500
-1
Wavenumber (cm ) Fig. 2. FTIR spectra of calcium carbonate nucleated (a) in the absence of the solution of oleic acid, (b) in the presence of the solution of oleic acid.
44
C. Wang et al. / Materials Science and Engineering C 27 (2007) 42–45
100
The active ratio (%)
80
60
40
20
0
Fig. 3. The contact angle of CaCO3 products obtained in the presence of the solution of oleic acid.
0.0
0.5
1.0
1.5
2.0
2.5
3.0
The weight ratio of oleic acid to calcium carbonate (%)
about 1 : 4) were obtained in the absence of the solution of oleic acid. However, in the presence of the solution of oleic acid, the ellipse-like CaCO3 particles in the average diameter of about 50 nm were synthesized as showed in Fig. 1b. We could conclude that oleic acid not only controls the growth of CaCO3 and but also changes the shape of final particles. Fig. 2 shows IR spectrums of the CaCO3 particles nucleated in the absence of and in the presence of the solution of oleic acid, respectively. The oleic acid absorption occurred around 2920 and 2853 cm− 1 which are consistent with the appearance of the alkyl groups from the oleic acid. The interaction characteristics of the modified CaCO3 surface were measured by contact angle in Fig. 3. The contact angle of the modified CaCO3 was 108.77 which showed that CaCO3 particles were of good hydrophobic property. The contact angles of the pellets after drying at 100 °C for 24h were not changed, which indicates that no volatile compounds were present in the samples. From the floating test, the active ratio of the products obtained reached 100%. The characteristics of oleic acid covered CaCO3 are shown in Table 1. The dispersabilities of T1 in organic solvents were significantly improved compared with that prepared without the oleic acid. Fig. 4 shows the results of the active ratio of CaCO3 particles nucleated in the presence of different weight ratio of oleic acid to CaCO3. When the weight ratio of oleic acid to CaCO3 changed from 0.3 to 0.6wt.%, the active ratio was 0% and the product were hydrophilic. It means that such weight ratio had no influence on the surface property of final CaCO3. The active
Fig. 4. Effects of the weight ratio of oleic acid to CaCO3 on the active ratio of hydrophobic CaCO3.
ratio increased step by step from 21% to 99.6% when the weight ratio of oleic acid to CaCO3 reached to 2.4 wt.% ml from 0.6 wt. %. With the increasing of the weight ratio to 2.7 wt.% or more, the active ratio reached to 100% and the product changed to hydrophobic completely from hydrophilic. It is of interest to know that the optimum weight ratio of oleic acid to CaCO3 is 2.7wt.%. In our opinion, when the weight ratio of oleic acid to CaCO3 was less than 0.6 wt.% there was no enough hydrophilic site to react with Ca2+, and the most of CaCO3 was uncovered.
Table 1 Dispersibility of T0 and T1 in organic solvents Run
Solvent
1 2 3 4
Toluene Cyclohexane Hexane DOP
Sedimentation time/min a T0
T1
b1 5 1 10
120 85 135 150
The amount of the solution of oleic acid is T0: 0ml, T1: 18ml. a Sedimentation time was determined using a dispersed solution (10 wt.%) at room temperature.
Ca2+
CO32-
CH3(CH2)7CH:CH(CH2)7COOH Ca(CH3(CH2)7CH:CH(CH2)7COO)2 Fig. 5. Schematic illustration for interaction between the organic substrate and inorganic mineral in aqueous medium.
20
30
40
50
45
salt of Ca(C17H33COO)2. Then CO2 gas was introduced into the stirred mixture at room temperature to synthesize CaCO3. The hydrophobic properties of the final CaCO3 nanoparticles were attributed to the deposition of the resulted Ca(C17H33COO)2 onto the surface of CaCO3. Nucleation of calcite is induced by carboxylate functional groups because the tridentate arrangement simulates the oxygen positions of carbonate anions lying parallel to this crystal surface. 4. Conclusion
(211) (122) (1010)
(018) (116) (024)
(202)
(113)
(110)
(006)
(012)
Intensity (a.u.)
(104)
C. Wang et al. / Materials Science and Engineering C 27 (2007) 42–45
60
2 Theta (degrees) Fig. 6. XRD patterns of CaCO3 particles nucleated in the organic substrate.
In contrast, the active ratio increased slowly relatively if the weight ratio increased up to 1.8wt.%. When the weight ratio reached to 2.7wt.% or more, the intact organic structure was formed to cover the surface of CaCO3 and make CaCO3 nanoparticles hydrophobic completely. Fig. 5 reveals the schematic illustration of interaction between the organic substrate and inorganic mineral in aqueous medium. In Fig. 6, the XRD result reveals that CaCO3 crystal obtained is calcite. CaðOHÞ2 →Ca2þ þ 2OH−
ð1Þ
Ca2þ þ C17 H33 COOH→CaðC17 H33 COOÞ2 þ 2Hþ
ð2Þ
CO2 þ H2 O→H2 CO3
ð3Þ
þ H2 CO3 →CO2− 3 þ 2H
ð4Þ
2þ CO2− 3 þ Ca →CaCO3
ð5Þ
In the present work, the oleic acid solution was added to the Ca(OH)2 slurry using a mechanical stirrer. In this reaction, Ca2+ ions of Ca(OH)2 reacted with oleic acid to form a hydrophobic
We have succeeded in surface modification of CaCO3 particles in situ with oleic acid in aqueous solution at room temperature. The oleic acid solution was used in precipitation process to control the particle size and to modify the surface of CaCO3 particles simultaneously. In this study the ellipse-like CaCO3 particles in the average diameter of about 50 nm can be synthesized. High weight ratio of oleic acid to CaCO3 promotes the active ratio of CaCO3 particles and an optimal weight ratio for this reaction is 18ml. References [1] K. Premphet, P. Horanont, Polymer 41 (2000) 9283. [2] L.J. Broutman, R.H. Krock, Compos. Mater. 6 (1974) 5. [3] Z. Demjén, B. Pukánszky, E. FÖldes, J. Nagy, J. Colloid Interface Sci. 190 (1997) 427. [4] S.J. Monte, G. Sugernam, Am. Chem. Soc. (1976) 43. [5] A.G. Xyla, P.G. Koutsoukos, J. Chem. Soc., Faraday Trans. 183 (1987) 1477. [6] K. Naka, Y. Chujo, Chem. Mater. 13 (2001) 3245. [7] Y. Levi, S. Albeck, A. brack, S. Weiner, L. Addadi, Chem. Eur. J. 4 (1998) 389. [8] L.A. Gower, D.A. Tirrell, J. Cryst. Growth 191 (1998) 153. [9] K. Naka, Y. Tanaka, Y. Chujo, Y. Ito, Chem. Commun. (1999) 1931. [10] C. Geffroy, A. Foissy, J. Persello, B. Cabane, J. Colloid Interface Sci. 211 (1999) 45. [11] J.M. Didymus, P. Oliver, S. Mann, A.L. Devires, P.V. Hauschka, P. Westbroek, J. Chem. Soc., Faraday Trans. 89 (1993) 2891. [12] Y. Ota, S. Inui, T. Iwashita, T. Kasuga, Y. Abe, J. Am. Ceram. Soc. 78 (1995) 1983. [13] M.M. Reddy, G.H. Nancollas, J. Colloid Interface Sci. 36 (1971) 166. [14] V.A. Juvekar, M.M. Sharam, Chem. Eng. Sci. 28 (1973) 825. [15] W.Z. Wang, G.H. Wang, Y.K. Liu, C.L. Zheng, Y.J. Zhan, J. Mater. Chem. 11 (2001) 1752. [16] Y. Sheng, B. Zhou, J.Z. Zhao, N.N. Tao, K.F. Yu, Y.M. Tian, Z.C. Wang, J. Colloid Interface Sci. 272 (2004) 326.
A novel aqueous-phase route to synthesize hydrophobic CaCO3 particles in situ Chengyu Wang, Ye Sheng, Hari-Bala, Xu Zhao, Jingzhe Zhao, Xiaokun Ma, Zichen Wang ⁎ Institute of Chemistry, Jilin University, Changchun 130023, China Received 22 November 2005; received in revised form 20 December 2005; accepted 12 January 2006 Available online 28 February 2006
Abstract Hydrophobic CaCO3 particles were prepared in situ by carbonation of Ca(OH)2 slurry in the presence of the ethanol solution of oleic acid by mimicking the process of biomineralization. The weight ratio of oleic acid to CaCO3 changed from 0.3 to 3 wt.%. By changing the weight ratio of oleic acid to CaCO3, the surface property of CaCO3 particles was changed from hydrophilic to hydrophobic. Floating test and contact angle analysis of the obtained product indicated that the final CaCO3 obtained was hydrophobic. From the floating test, the active ratio of the modified CaCO3 might reach 100%. The contact angle of the modified CaCO3 was 108.77. IR spectrums of the CaCO3 particles showed the appearance of the alkyl groups from the oleic acid. We have succeeded in surface modification of CaCO3 with the hydrophobic oleic acid. © 2006 Elsevier B.V. All rights reserved. Keywords: Calcium carbonate; Hydrophobic; Oleic acid; Carbonation; Organic substrate
1. Introduction CaCO3 is one of the important fillers used in the industries of plastics, rubber, paint, and so on. One of the most problematic issues for the use of CaCO3 is the hydrophilic property, and this problem makes it very difficult to be used widely. Surface modification of CaCO3 with hydrophobic species would lead to a great expansion in its applications; since mineral particles are hardly dispersed in a polymer matrix [1]. The modification of the surface by surfactants has been extensively studied. For example, the surfactants containing reactive functional groups such as silane coupling agents [2,3], titanate coupling agents [4], or stearic acid [5] can all improve the hydrophobic properties of CaCO3. However, all the processes were conducted with the resultant CaCO3 products rather than during the synthesis process of CaCO3. Recently, the synthesis of organic–inorganic hybrids by mimicking biomineralization has attracted great attention [6]. Crystallization of CaCO3 in the presence of various additives and synthetic polymers has been investigated as a model of biomineralization [7–9]. It has been known that organic additives introduced to the crystallization ⁎ Corresponding author. E-mail address: [email protected] (Z. Wang). 0928-4931/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.msec.2006.01.003
process of CaCO3 modify the shapes of crystals [10,11] and control the nucleation and growth of particles, but there were still no the reports that the organic additives change the property of inorganic mineral in situ. In this paper, we paid our attention to the study of modification in situ by mimicking the process of biomineralization. Synthesis of CaCO3 was followed by two basic synthetic routes: (1) the solution route [12,13], through a double decomposition reaction, wherein aqueous CaCl2 and NaCO3, or CaCl2 and (NH4)2CO3, or Ca(NO3)2 and NaCO3 are combined in an equal molar ratio; and (2) the carbonation method [14], in which CO2 gas is bubbled through an aqueous slurry of Ca(OH)2. The latter is preferred in terms of environment preservation and the effective use of mineral resources. The carbonation method is an industrially useful method, but it is difficult to control the crystal shape and modification of CaCO3 [15]. Here, hydrophobic CaCO3 particles were synthesized in situ in aqueous solution by carbonation method. The oleic acid used as organic additive not only controls the nucleation and growth of CaCO3 but also modify the surface of CaCO3. Although many studies have shown that a lot of additives can influence the shape of crystals under laboratory conditions, the oleic acid has not been used for the crystallization of CaCO3. Meanwhile, the presence of CjC
C. Wang et al. / Materials Science and Engineering C 27 (2007) 42–45
43
Fig. 1. TEM of CaCO3 products obtained (a) in the absence of the solution of oleic acid, (b) in the presence of the solution of oleic acid.
All of the chemical reagents used in this experiment were of analytical grade. The procedure employed for the synthesis of CaCO3 was as follows. 10 g of CaO was digested in 100 ml of 80 °C distilled water to form Ca(OH)2 slurry. After a day, the slurry was filtered through a 200 mesh sieve in order to remove the impurity and large particles and then transferred into a 250 ml three-necked flask. After addition of the ethanol solution of oleic acid (0.1 M) into the flask, the mixture was stirred vigorously for 2 h at room temperature using a mechanical stirrer in order to ensure that the COO− of oleic acid could react with Ca2+. Then CO2 gas was introduced into the mixture through a tube while the mixture was stirred at the same time. The reaction was performed at ambient reaction condition and controlled by the pH of the medium. The reaction was stopped when the final pH value of suspension reached about 7. The precipitates were separated from the mother liquid by filtration and rinsed three times with absolute ethanol to remove remaining oleic acid. The final product was dried for 1day in an oven at 100 °C. The morphology and particle size of the products were characterized by virtue of transmission electron micrograph (TEM). TEM measurement was carried out on a Hitachi 8100 IV at 100kV. The crystalline phase of the synthesized CaCO3 was characterized by X-ray diffraction (XRD) analysis with a Shimadju D/max-rA X-ray diffractometer with Cu Ka radiation (λ = 0.15418 nm), accelerating voltage being 40 kV, current 30 mA, and scanning rate 4 °/min. In order to study the surface characteristic, Fourier transform infrared spectroscopy (RT-IR) was recorded on an Ominic system 2000 with the KBr pellet method.
3. Results and discussion From Fig. 1a we could see that the spindle-like CaCO3 with the diameter of about 100nm (the ratio of diameter to length
a
b
2920 2853
2. Experimental
The effect of surface modification was evaluated by the relative contact angle and active ratio. The contact angle was measured at 25 °C with a FTÅ200 (USA) contact angle analyzer. On flat solid surfaces, the contact angle can be measured by the sessile drop technique. The powdery samples (1g) in 10MPa pressure were first pressed into thin pellet and then the water droplet was dropped onto the pellet. The contact angle against water on a horizontal surface of a pellet was obtained. The effect of surface modification was evaluated by the floating test [16]. 10 g of the final sample was put into 100ml of water. We measured the ratio of floated product to overall weight of sample after they was mixed in water and stirred vigorously. This ratio was called the active ratio. The higher the active ratio, the better the hydrophobic property was.
Transmittance
bonds of oleic acid makes the final products easily react with polymer matrix. Using this method, it is easy to synthesize hydrophobic CaCO3 particles in the presence of oleic acid at ambient reaction conditions and is potentially important for industrial process of biomineralization.
3500
3000
2500
2000
1500
1000
500
-1
Wavenumber (cm ) Fig. 2. FTIR spectra of calcium carbonate nucleated (a) in the absence of the solution of oleic acid, (b) in the presence of the solution of oleic acid.
44
C. Wang et al. / Materials Science and Engineering C 27 (2007) 42–45
100
The active ratio (%)
80
60
40
20
0
Fig. 3. The contact angle of CaCO3 products obtained in the presence of the solution of oleic acid.
0.0
0.5
1.0
1.5
2.0
2.5
3.0
The weight ratio of oleic acid to calcium carbonate (%)
about 1 : 4) were obtained in the absence of the solution of oleic acid. However, in the presence of the solution of oleic acid, the ellipse-like CaCO3 particles in the average diameter of about 50 nm were synthesized as showed in Fig. 1b. We could conclude that oleic acid not only controls the growth of CaCO3 and but also changes the shape of final particles. Fig. 2 shows IR spectrums of the CaCO3 particles nucleated in the absence of and in the presence of the solution of oleic acid, respectively. The oleic acid absorption occurred around 2920 and 2853 cm− 1 which are consistent with the appearance of the alkyl groups from the oleic acid. The interaction characteristics of the modified CaCO3 surface were measured by contact angle in Fig. 3. The contact angle of the modified CaCO3 was 108.77 which showed that CaCO3 particles were of good hydrophobic property. The contact angles of the pellets after drying at 100 °C for 24h were not changed, which indicates that no volatile compounds were present in the samples. From the floating test, the active ratio of the products obtained reached 100%. The characteristics of oleic acid covered CaCO3 are shown in Table 1. The dispersabilities of T1 in organic solvents were significantly improved compared with that prepared without the oleic acid. Fig. 4 shows the results of the active ratio of CaCO3 particles nucleated in the presence of different weight ratio of oleic acid to CaCO3. When the weight ratio of oleic acid to CaCO3 changed from 0.3 to 0.6wt.%, the active ratio was 0% and the product were hydrophilic. It means that such weight ratio had no influence on the surface property of final CaCO3. The active
Fig. 4. Effects of the weight ratio of oleic acid to CaCO3 on the active ratio of hydrophobic CaCO3.
ratio increased step by step from 21% to 99.6% when the weight ratio of oleic acid to CaCO3 reached to 2.4 wt.% ml from 0.6 wt. %. With the increasing of the weight ratio to 2.7 wt.% or more, the active ratio reached to 100% and the product changed to hydrophobic completely from hydrophilic. It is of interest to know that the optimum weight ratio of oleic acid to CaCO3 is 2.7wt.%. In our opinion, when the weight ratio of oleic acid to CaCO3 was less than 0.6 wt.% there was no enough hydrophilic site to react with Ca2+, and the most of CaCO3 was uncovered.
Table 1 Dispersibility of T0 and T1 in organic solvents Run
Solvent
1 2 3 4
Toluene Cyclohexane Hexane DOP
Sedimentation time/min a T0
T1
b1 5 1 10
120 85 135 150
The amount of the solution of oleic acid is T0: 0ml, T1: 18ml. a Sedimentation time was determined using a dispersed solution (10 wt.%) at room temperature.
Ca2+
CO32-
CH3(CH2)7CH:CH(CH2)7COOH Ca(CH3(CH2)7CH:CH(CH2)7COO)2 Fig. 5. Schematic illustration for interaction between the organic substrate and inorganic mineral in aqueous medium.
20
30
40
50
45
salt of Ca(C17H33COO)2. Then CO2 gas was introduced into the stirred mixture at room temperature to synthesize CaCO3. The hydrophobic properties of the final CaCO3 nanoparticles were attributed to the deposition of the resulted Ca(C17H33COO)2 onto the surface of CaCO3. Nucleation of calcite is induced by carboxylate functional groups because the tridentate arrangement simulates the oxygen positions of carbonate anions lying parallel to this crystal surface. 4. Conclusion
(211) (122) (1010)
(018) (116) (024)
(202)
(113)
(110)
(006)
(012)
Intensity (a.u.)
(104)
C. Wang et al. / Materials Science and Engineering C 27 (2007) 42–45
60
2 Theta (degrees) Fig. 6. XRD patterns of CaCO3 particles nucleated in the organic substrate.
In contrast, the active ratio increased slowly relatively if the weight ratio increased up to 1.8wt.%. When the weight ratio reached to 2.7wt.% or more, the intact organic structure was formed to cover the surface of CaCO3 and make CaCO3 nanoparticles hydrophobic completely. Fig. 5 reveals the schematic illustration of interaction between the organic substrate and inorganic mineral in aqueous medium. In Fig. 6, the XRD result reveals that CaCO3 crystal obtained is calcite. CaðOHÞ2 →Ca2þ þ 2OH−
ð1Þ
Ca2þ þ C17 H33 COOH→CaðC17 H33 COOÞ2 þ 2Hþ
ð2Þ
CO2 þ H2 O→H2 CO3
ð3Þ
þ H2 CO3 →CO2− 3 þ 2H
ð4Þ
2þ CO2− 3 þ Ca →CaCO3
ð5Þ
In the present work, the oleic acid solution was added to the Ca(OH)2 slurry using a mechanical stirrer. In this reaction, Ca2+ ions of Ca(OH)2 reacted with oleic acid to form a hydrophobic
We have succeeded in surface modification of CaCO3 particles in situ with oleic acid in aqueous solution at room temperature. The oleic acid solution was used in precipitation process to control the particle size and to modify the surface of CaCO3 particles simultaneously. In this study the ellipse-like CaCO3 particles in the average diameter of about 50 nm can be synthesized. High weight ratio of oleic acid to CaCO3 promotes the active ratio of CaCO3 particles and an optimal weight ratio for this reaction is 18ml. References [1] K. Premphet, P. Horanont, Polymer 41 (2000) 9283. [2] L.J. Broutman, R.H. Krock, Compos. Mater. 6 (1974) 5. [3] Z. Demjén, B. Pukánszky, E. FÖldes, J. Nagy, J. Colloid Interface Sci. 190 (1997) 427. [4] S.J. Monte, G. Sugernam, Am. Chem. Soc. (1976) 43. [5] A.G. Xyla, P.G. Koutsoukos, J. Chem. Soc., Faraday Trans. 183 (1987) 1477. [6] K. Naka, Y. Chujo, Chem. Mater. 13 (2001) 3245. [7] Y. Levi, S. Albeck, A. brack, S. Weiner, L. Addadi, Chem. Eur. J. 4 (1998) 389. [8] L.A. Gower, D.A. Tirrell, J. Cryst. Growth 191 (1998) 153. [9] K. Naka, Y. Tanaka, Y. Chujo, Y. Ito, Chem. Commun. (1999) 1931. [10] C. Geffroy, A. Foissy, J. Persello, B. Cabane, J. Colloid Interface Sci. 211 (1999) 45. [11] J.M. Didymus, P. Oliver, S. Mann, A.L. Devires, P.V. Hauschka, P. Westbroek, J. Chem. Soc., Faraday Trans. 89 (1993) 2891. [12] Y. Ota, S. Inui, T. Iwashita, T. Kasuga, Y. Abe, J. Am. Ceram. Soc. 78 (1995) 1983. [13] M.M. Reddy, G.H. Nancollas, J. Colloid Interface Sci. 36 (1971) 166. [14] V.A. Juvekar, M.M. Sharam, Chem. Eng. Sci. 28 (1973) 825. [15] W.Z. Wang, G.H. Wang, Y.K. Liu, C.L. Zheng, Y.J. Zhan, J. Mater. Chem. 11 (2001) 1752. [16] Y. Sheng, B. Zhou, J.Z. Zhao, N.N. Tao, K.F. Yu, Y.M. Tian, Z.C. Wang, J. Colloid Interface Sci. 272 (2004) 326.