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Surface modification of spherical magnesium oxide with ethylene glycol
Materials Letters 63 (2009) 1514–1516
Contents lists available at ScienceDirect
Materials Letters j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e / m a t l e t
Surface modification of spherical magnesium oxide with ethylene glycol Jing Jin a,b, Zhiping Zhang c, Huilian Ma a, Xianbo Lu a, Jiping Chen a,⁎, Qing Zhang a, Haijun Zhang a, Yuwen Ni a a b c
Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China Graduate University of Chinese Academy of Science, Beijing 100039, China Brigham Young University, Provo 84602, USA
a r t i c l e
i n f o
Article history: Received 12 March 2009 Accepted 1 April 2009 Available online 6 April 2009 Keywords: Spherical Magnesium oxide Modification Ethylene glycol Surface area Pore size
a b s t r a c t The surface of spherical magnesium oxide has been modified with ethylene glycol in the presence of basic aqueous solution. Fourier transform infrared spectra have shown the presence of the graft group ethylene glycol on the surface of spherical magnesium oxide. In addition, this conclusion can also be drawn from appearance of new diffraction peak in X-ray diffraction pattern. Although magnesium oxide microspheres can directly react with ethylene glycol in 373 K for 24 h, owing to Lewis acid and alkali interaction, product derived is colloidal and difficult to filter so that their morphology is easy to be destroyed. However, in the presence of basic aqueous solution, their morphology still retains. The modified magnesium oxide illustrates a specific surface area of 55.9 m2/g and a narrow pore size distribution centered at 8.96 nm. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Magnesium oxide (MgO) is one of the most useful ceramic materials. In recent years, it has received special attention because of its important applications in catalysis, toxic waste remediation, refractory materials, superconductors, or as additives in paint [1–4]. Different morphologies of MgO, such as flowerlike nanostructures [5], nanotube [6], nanoplate [7], and microsphere [8] and so on, have been prepared. However, there are few reports on the modification of MgO with different organic groups. For example, Jiang and Huang [9] investigated the radiation-induced graft polymerization of methyl methacrylate on MgO surface. Wang et al. reported the graft copolymerization of butyl acrylate on the surface of MgO by 60Co radiation [10]. Hu and Zheng studied the modification of MgO surface with sodium dodecylbenzenesulfonate, stearic acid, sodium lauryl sulfate and hexadecyltrimethyl ammonium bromide, and found that nanometer MgO can be well modified with stearic acid [11]. Although MgO surface has been modified with above different groups, it is still a great challenge to modify MgO with well-defined shape under mild conditions. In our recent report, monodisperse MgO microspheres have been synthesized by a facile seed-induced precipitation [8]. After investigation of their chromatographic properties, the particles illustrated a potential in the separation of polycyclic aromatic hydrocarbons and basic compounds as a packing material in normal-phase liquid chromatography (LC) [12]. Unfortunately, such MgO microspheres, ⁎ Corresponding author. Tel./fax: +86 411 84379562. E-mail address: [email protected] (J. Chen). 0167-577X/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2009.04.003
similar to other packing materials (e.g., silica, titania and zirconia), cannot be used a packing for reversed-phase before modification with organic groups. In this report, attempts have been made to modify these MgO microspheres with ethylene glycol on the basis of previous report [13]. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM) and nitrogen adsorption/desorption techniques are also used to characterize the obtained products. 2. Experimental The procedure for the preparation of spherical MgO was same as that in our recent report [12]. The process for the modification of
Fig. 1. FT-IR spectra of MgO and MgO–EG.
J. Jin et al. / Materials Letters 63 (2009) 1514–1516
Fig. 2. X-ray diffraction patterns of MgO and MgO–EG.
monodisperse MgO microspheres is as below. In a typical synthesis, 2 g of KOH was firstly dissolved into 10 mL of Milli-Q water, and then above solution was mixed with 135 mL of ethylene glycol. Under stirring, 3 g of the obtained MgO was added into the mixture. After maintaining at 373 K for 24 h under gently stirring, the obtained white powders were filtered, washed by water and ethanol for several times and then dried. The Fourier transform infrared (FT-IR) spectra were recorded using a Perkin-Elmer GS-II FT-IR spectrometer in the range of 4000–400 cm− 1, with a resolution of 4 cm− 1 and accumulation of 8 scans. The crystal structures of these products were characterized by XRD on a Philips CM1 diffractometer using Cu Kα radiation (λ = 0.1543 nm), and the operation voltage was 40 kV and the current was 40 mA. The SEM images were taken with a JSM-6360LV scanning electron microscope operated at 24 kV. Nitrogen adsorption isotherms were measured at 77 K on a NOVA 4000 nitrogen adsorption apparatus. Before measurements, the samples were out-gassed at 473 K for 5 h. 3. Results and discussion Prior to characterization, several factors are optimized, shown in Fig. S1–S3 of the Supporting information. On the one hand, lower temperature leads to lower reaction efficiency and higher tempera-
1515
ture leads to side reaction, decreasing reaction efficiency in the same way (Fig. S1); On the other hand, in order to gain stronger intensity of C–H stretching bands and weaker intensity of dissociative hydroxyl and also keep spherical morphology not to be destroyed (Fig. S2–S3), the optimized conditions are drawn as described in the Experimental section. In basic aqueous solution, presupposing the formation of brucite, not only MgO self react with ethylene glycol on the basis of Lewis acid and alkali interaction (Fig. S4), but also brucite deposited on the top of MgO as reported before [13]. Fig. 1 shows the FT-IR spectrum of spherical MgO and that of MgO–EG derived at optimized conditions. As can bee seen, not only some new absorption bands appear, but also absorption bands attributed to MgO shift in FT-IR spectrum of MgO– EG. These important information in the 2700–3000 cm− 1 and 1030– 1100 cm− 1 region of the FT-IR spectra forcefully proved ethylene glycol grafted MgO and brucite, similar to previous reports [13–15]. Fig. 2 exemplifies the XRD patterns for MgO and MgO–EG. The former is in agreement with the previous report [2]. By comparison, one can see that the patterns of two samples all consist of sharp diffraction peaks. In addition, it appears broad peaks at the 2θ = 10.9° and 59.4° for MgO–EG, attributed to the packing of brucite layers after grafting with EG, in agreement with the literatures [13,16]. Fig. 3 shows the SEM images of as-synthesized MgO microspheres and Mg–EG. Before modification, the products demonstrate well dispersed microspheres with a diameter of about 9.5 µm as given in Fig. 3(A), and their particles are self-assembled by nanosheets with a thickness of ca. 30–50 nm (Fig. 3(B)). After modifying these particles with ethylene glycol at 373 K for 24 h, the obtained particles still remain spherical structure as illustrated in Fig. 3(C). In contrast to the particles prior to modification, however, the surface for Mg–EG is covered by some gel-like products, and also becomes coarser, which is obvious in Fig. 3(D). The surface differences between them could be attributed to ethylene glycol grafted MgO and brucite. The typical nitrogen adsorption/desorption isotherms for MgO and MgO–EG, as well as their corresponding pore size distributions, are shown in Fig. 4. The nitrogen adsorption isotherm for MgO microspheres could be classified as type-IV with H3 hysteresis loop according to the IUPAC nomenclature, and the pore diameter is 15.8 nm. With the modification of these particles by ethylene glycol,
Fig. 3. SEM images of (A, B) MgO and (C, D) MgO–EG at low/high magnifications.
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J. Jin et al. / Materials Letters 63 (2009) 1514–1516
Fig. 4. (A) N2 adsorption/desorption isotherm plots of MgO and MgO–EG. (B) BJH pore size of distribution of MgO and MgO–EG.
the adsorption isotherm can also be assigned to type-IV, but the hysteresis loop changes to the one between H2 and H3. The narrower pore size distribution centered at 8.96 nm, to a certain extent, also demonstrates this type of hysteresis loop. The specific surface area of the obtained MgO–EG is 55.9 m2/g with corresponding total pore volumes of 0.1251 cm3/g. 4. Conclusions Monodisperse MgO microspheres have been successfully modified with ethylene glycol in basic aqueous solution system. Not only MgO self reacts with ethylene glycol by Lewis acid and alkali interaction, but also brucite covering MgO surface to some extent, producing pillars of EG between the brucite layers. The characteristics of MgO– EG such as regular shape and narrow pore size distribution, is expected to find a potential applications in separation, catalysis and other fields, and the relevant work is still in progress. Acknowledgement This research was supported by the National Natural Science Foundation of China (Grant No.20775081).
Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.matlet.2009.04.003. References [1] Li WC, Lu AH, Weidenthaler C, Schüth F. Chem Mater 2004;16:5676–81. [2] Makhluf S, Dror R, Nitzan Y, Abramovich Y, Jelinek R, Gedanken A. Adv Funct Mater 2005;18:1708–15. [3] Choudary BM, Mulukutla RS, Klabunde KJ. J Am Chem Soc 2003;125:2020–1. [4] Rajagopalan S, Koper O, Decker S, Klabunde KJ. Chem Eur J 2002;8:2602–7. [5] Bain SW, Ma Z, Cui ZM, Zhang LS, Niu F, Song WG. J Phys Chem, C 2008;112:11340–4. [6] Zhan J, Bando Y, Hu J, Golberg D. Inorg Chem 2004;43:2462–4. [7] Yu JC, Xu A, Zhang L, Song R, Wu L. J Phys Chem, B 2004;108:64–70. [8] Zhang ZP, Zheng YJ, Chen JP, Zhang Q, Ni YW, Liang XM. Adv Funct Mater 2007;17:2447–54. [9] Jiang B, Huang G. Radiat Phys Chem 2004;69:433–8. [10] Wang J, Cao G, Tang XH. J Jinan Univ Nat Sci Ed 2005;26:667–71 [Chinese]. [11] Hu ZW, Zheng LJ. J Anhui Univ Technol Sci 2006;21:4–7 [Chinese]. [12] Zhang ZP, Zheng YJ, Zhang JX, Chen JP, Liang XM. J Chromatogr, A 2007;1165:116–21. [13] Wypych F, Schreiner WH, Marangoni R. Colloid Interface Sci 2002;253:180–4. [14] Tunney J, Detelier C. Clays Clay Miner 1994;42:552. [15] Herreros B, Barr TL, Klinowski J. J Phys Chem 1994;98:738–41. [16] Clifford YT, Chia-Te T, Chang MH, Liu HS. Ind Eng Chem Res 2007;46:5536–41.
Contents lists available at ScienceDirect
Materials Letters j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e / m a t l e t
Surface modification of spherical magnesium oxide with ethylene glycol Jing Jin a,b, Zhiping Zhang c, Huilian Ma a, Xianbo Lu a, Jiping Chen a,⁎, Qing Zhang a, Haijun Zhang a, Yuwen Ni a a b c
Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China Graduate University of Chinese Academy of Science, Beijing 100039, China Brigham Young University, Provo 84602, USA
a r t i c l e
i n f o
Article history: Received 12 March 2009 Accepted 1 April 2009 Available online 6 April 2009 Keywords: Spherical Magnesium oxide Modification Ethylene glycol Surface area Pore size
a b s t r a c t The surface of spherical magnesium oxide has been modified with ethylene glycol in the presence of basic aqueous solution. Fourier transform infrared spectra have shown the presence of the graft group ethylene glycol on the surface of spherical magnesium oxide. In addition, this conclusion can also be drawn from appearance of new diffraction peak in X-ray diffraction pattern. Although magnesium oxide microspheres can directly react with ethylene glycol in 373 K for 24 h, owing to Lewis acid and alkali interaction, product derived is colloidal and difficult to filter so that their morphology is easy to be destroyed. However, in the presence of basic aqueous solution, their morphology still retains. The modified magnesium oxide illustrates a specific surface area of 55.9 m2/g and a narrow pore size distribution centered at 8.96 nm. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Magnesium oxide (MgO) is one of the most useful ceramic materials. In recent years, it has received special attention because of its important applications in catalysis, toxic waste remediation, refractory materials, superconductors, or as additives in paint [1–4]. Different morphologies of MgO, such as flowerlike nanostructures [5], nanotube [6], nanoplate [7], and microsphere [8] and so on, have been prepared. However, there are few reports on the modification of MgO with different organic groups. For example, Jiang and Huang [9] investigated the radiation-induced graft polymerization of methyl methacrylate on MgO surface. Wang et al. reported the graft copolymerization of butyl acrylate on the surface of MgO by 60Co radiation [10]. Hu and Zheng studied the modification of MgO surface with sodium dodecylbenzenesulfonate, stearic acid, sodium lauryl sulfate and hexadecyltrimethyl ammonium bromide, and found that nanometer MgO can be well modified with stearic acid [11]. Although MgO surface has been modified with above different groups, it is still a great challenge to modify MgO with well-defined shape under mild conditions. In our recent report, monodisperse MgO microspheres have been synthesized by a facile seed-induced precipitation [8]. After investigation of their chromatographic properties, the particles illustrated a potential in the separation of polycyclic aromatic hydrocarbons and basic compounds as a packing material in normal-phase liquid chromatography (LC) [12]. Unfortunately, such MgO microspheres, ⁎ Corresponding author. Tel./fax: +86 411 84379562. E-mail address: [email protected] (J. Chen). 0167-577X/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2009.04.003
similar to other packing materials (e.g., silica, titania and zirconia), cannot be used a packing for reversed-phase before modification with organic groups. In this report, attempts have been made to modify these MgO microspheres with ethylene glycol on the basis of previous report [13]. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM) and nitrogen adsorption/desorption techniques are also used to characterize the obtained products. 2. Experimental The procedure for the preparation of spherical MgO was same as that in our recent report [12]. The process for the modification of
Fig. 1. FT-IR spectra of MgO and MgO–EG.
J. Jin et al. / Materials Letters 63 (2009) 1514–1516
Fig. 2. X-ray diffraction patterns of MgO and MgO–EG.
monodisperse MgO microspheres is as below. In a typical synthesis, 2 g of KOH was firstly dissolved into 10 mL of Milli-Q water, and then above solution was mixed with 135 mL of ethylene glycol. Under stirring, 3 g of the obtained MgO was added into the mixture. After maintaining at 373 K for 24 h under gently stirring, the obtained white powders were filtered, washed by water and ethanol for several times and then dried. The Fourier transform infrared (FT-IR) spectra were recorded using a Perkin-Elmer GS-II FT-IR spectrometer in the range of 4000–400 cm− 1, with a resolution of 4 cm− 1 and accumulation of 8 scans. The crystal structures of these products were characterized by XRD on a Philips CM1 diffractometer using Cu Kα radiation (λ = 0.1543 nm), and the operation voltage was 40 kV and the current was 40 mA. The SEM images were taken with a JSM-6360LV scanning electron microscope operated at 24 kV. Nitrogen adsorption isotherms were measured at 77 K on a NOVA 4000 nitrogen adsorption apparatus. Before measurements, the samples were out-gassed at 473 K for 5 h. 3. Results and discussion Prior to characterization, several factors are optimized, shown in Fig. S1–S3 of the Supporting information. On the one hand, lower temperature leads to lower reaction efficiency and higher tempera-
1515
ture leads to side reaction, decreasing reaction efficiency in the same way (Fig. S1); On the other hand, in order to gain stronger intensity of C–H stretching bands and weaker intensity of dissociative hydroxyl and also keep spherical morphology not to be destroyed (Fig. S2–S3), the optimized conditions are drawn as described in the Experimental section. In basic aqueous solution, presupposing the formation of brucite, not only MgO self react with ethylene glycol on the basis of Lewis acid and alkali interaction (Fig. S4), but also brucite deposited on the top of MgO as reported before [13]. Fig. 1 shows the FT-IR spectrum of spherical MgO and that of MgO–EG derived at optimized conditions. As can bee seen, not only some new absorption bands appear, but also absorption bands attributed to MgO shift in FT-IR spectrum of MgO– EG. These important information in the 2700–3000 cm− 1 and 1030– 1100 cm− 1 region of the FT-IR spectra forcefully proved ethylene glycol grafted MgO and brucite, similar to previous reports [13–15]. Fig. 2 exemplifies the XRD patterns for MgO and MgO–EG. The former is in agreement with the previous report [2]. By comparison, one can see that the patterns of two samples all consist of sharp diffraction peaks. In addition, it appears broad peaks at the 2θ = 10.9° and 59.4° for MgO–EG, attributed to the packing of brucite layers after grafting with EG, in agreement with the literatures [13,16]. Fig. 3 shows the SEM images of as-synthesized MgO microspheres and Mg–EG. Before modification, the products demonstrate well dispersed microspheres with a diameter of about 9.5 µm as given in Fig. 3(A), and their particles are self-assembled by nanosheets with a thickness of ca. 30–50 nm (Fig. 3(B)). After modifying these particles with ethylene glycol at 373 K for 24 h, the obtained particles still remain spherical structure as illustrated in Fig. 3(C). In contrast to the particles prior to modification, however, the surface for Mg–EG is covered by some gel-like products, and also becomes coarser, which is obvious in Fig. 3(D). The surface differences between them could be attributed to ethylene glycol grafted MgO and brucite. The typical nitrogen adsorption/desorption isotherms for MgO and MgO–EG, as well as their corresponding pore size distributions, are shown in Fig. 4. The nitrogen adsorption isotherm for MgO microspheres could be classified as type-IV with H3 hysteresis loop according to the IUPAC nomenclature, and the pore diameter is 15.8 nm. With the modification of these particles by ethylene glycol,
Fig. 3. SEM images of (A, B) MgO and (C, D) MgO–EG at low/high magnifications.
1516
J. Jin et al. / Materials Letters 63 (2009) 1514–1516
Fig. 4. (A) N2 adsorption/desorption isotherm plots of MgO and MgO–EG. (B) BJH pore size of distribution of MgO and MgO–EG.
the adsorption isotherm can also be assigned to type-IV, but the hysteresis loop changes to the one between H2 and H3. The narrower pore size distribution centered at 8.96 nm, to a certain extent, also demonstrates this type of hysteresis loop. The specific surface area of the obtained MgO–EG is 55.9 m2/g with corresponding total pore volumes of 0.1251 cm3/g. 4. Conclusions Monodisperse MgO microspheres have been successfully modified with ethylene glycol in basic aqueous solution system. Not only MgO self reacts with ethylene glycol by Lewis acid and alkali interaction, but also brucite covering MgO surface to some extent, producing pillars of EG between the brucite layers. The characteristics of MgO– EG such as regular shape and narrow pore size distribution, is expected to find a potential applications in separation, catalysis and other fields, and the relevant work is still in progress. Acknowledgement This research was supported by the National Natural Science Foundation of China (Grant No.20775081).
Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.matlet.2009.04.003. References [1] Li WC, Lu AH, Weidenthaler C, Schüth F. Chem Mater 2004;16:5676–81. [2] Makhluf S, Dror R, Nitzan Y, Abramovich Y, Jelinek R, Gedanken A. Adv Funct Mater 2005;18:1708–15. [3] Choudary BM, Mulukutla RS, Klabunde KJ. J Am Chem Soc 2003;125:2020–1. [4] Rajagopalan S, Koper O, Decker S, Klabunde KJ. Chem Eur J 2002;8:2602–7. [5] Bain SW, Ma Z, Cui ZM, Zhang LS, Niu F, Song WG. J Phys Chem, C 2008;112:11340–4. [6] Zhan J, Bando Y, Hu J, Golberg D. Inorg Chem 2004;43:2462–4. [7] Yu JC, Xu A, Zhang L, Song R, Wu L. J Phys Chem, B 2004;108:64–70. [8] Zhang ZP, Zheng YJ, Chen JP, Zhang Q, Ni YW, Liang XM. Adv Funct Mater 2007;17:2447–54. [9] Jiang B, Huang G. Radiat Phys Chem 2004;69:433–8. [10] Wang J, Cao G, Tang XH. J Jinan Univ Nat Sci Ed 2005;26:667–71 [Chinese]. [11] Hu ZW, Zheng LJ. J Anhui Univ Technol Sci 2006;21:4–7 [Chinese]. [12] Zhang ZP, Zheng YJ, Zhang JX, Chen JP, Liang XM. J Chromatogr, A 2007;1165:116–21. [13] Wypych F, Schreiner WH, Marangoni R. Colloid Interface Sci 2002;253:180–4. [14] Tunney J, Detelier C. Clays Clay Miner 1994;42:552. [15] Herreros B, Barr TL, Klinowski J. J Phys Chem 1994;98:738–41. [16] Clifford YT, Chia-Te T, Chang MH, Liu HS. Ind Eng Chem Res 2007;46:5536–41.