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The effect of the divalent metal on the intercalation capacity of stearate anions into layered double hydroxide nanolayers
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JIEC 2101 1–7 Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx
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The effect of the divalent metal on the intercalation capacity of stearate anions into layered double hydroxide nanolayers Eili a,*, Kamyar Shameli b,**, Nor Azowa Ibrahim b, Mansor Bin Ahmad b, Wan Md Zin Wan Yunus c
Q1 Mahboobeh
a
Faculty of Basic Sciences and Advanced Technologies, University of Science and Culture, Park Avenue, Ashrafi Esfahani Boulevard, Tehran IR14536-33143, Iran b Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Serdang, Selangor 43400, Malaysia c Department of Chemistry, Centre for Defence Foundation Studies, National Defence University of Malaysia, Kuala Lumpur 57000, Malaysia
A R T I C L E I N F O
A B S T R A C T
Article history: Received 21 February 2014 Accepted 16 June 2014 Available online xxx
A comparison has been made of the intercalation capacity of the stearate anions into the two different anionic clays: magnesium aluminum layered double hydroxide (Mg3Al LDH) and zinc aluminum layered double hydroxide (Zn3Al LDH). The anionic clays Mg3Al LDH and Zn3Al LDH were firstly prepared by coprecipitation method from nitrate salts solution and then modified by stearate anions through an ion exchange reaction. The properties, morphologies and ion exchange ability of these two clays have been studied by XRD, TGA, SEM, TEM and CHNS that show the ability of Zn3Al LDH to capture stearate anions is greater than Mg3Al LDH. ß 2014 Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering Chemistry.
Keywords: Layered double hydroxide Comparison Intercalation capacity Elemental analysis Thermogravimetric analysis
10 11
Introduction
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Layered structure solids are very useful materials because of their wide potential applications in different fields such as catalysts [1], ion exchangers [2], sorbents [3], and electrochemistry [4]. They can divided into different groups, taking into account the charge excess within the layers, include negatively charged layers solids like montmorillonite, positively charged layers solids like layered double hydroxide (LDH) and neutrally charged layers such as mica and graphite [5]. Among these materials both phyllosilicate clays and LDHs have attracted an increasing amount of attention due to the presence of electrical charges within the layers and therefore their capability to ion-exchange that is an important property for different applications. However, LDHs present certain specific advantages, which are lacking in layered silicates type nanoclays such as their relative ease and low cost of synthesis, thermal and chemical stability, surface properties, nontoxicity, adjustability of their particle size and aspect ratio by changing the reaction conditions and the wide range of choice for surfactants like fatty acid salts, sulfonates,
* Corresponding author. ** Corresponding author. Tel.: +60 3 8946 6775; fax: +60 3 8943 5380. E-mail addresses: [email protected] (M. Eili), [email protected] (K. Shameli).
sulfates, phosphates, etc., that can intercalated between the layers for extensive applications in different fields [6–8]. Layered double hydroxides (LDHs) are anionic clays which can X be represented as ½MðIIÞ1X MðIIIÞX ðOHÞ2 Xþ ½An where X=n mH2 O M(II) and M(III) are divalent and trivalent cations, respectively, and An is an exchangeable anion [9,10]. LDHs are composed of octahedral M2+(OH)6 brucite-like layers which are positively charged by the partial substitution of M3+ for M2+. Thus, anions are intercalated into the interlayers in order to compensate the positive layer charges [11,12]. Every M(II) and M(III) ions which have similar ionic radius to accommodate in the holes of the close packed configuration of OH groups in the brucite-like layers can form LDH but depend on the nature of cations, the obtained LDH can have different physical characteristics such as surface basicity and ion exchange capacity [13,14]. LDHs with different cations, such as Mg, Mn, Fe, Co, Ni, Cu, and Zn for divalent cations and Al, Mn, Fe, Co, Ni, Cr, and Ga for trivalent cations have been studied, however, the most reported have been focused on using MgAl LDH and ZnAl LDH, since zinc, magnesium and aluminum yield more environmentally friendly materials [8,15–17]. Inorganic–organic nanocomposite materials with functional organic compounds immobilized into a layered inorganic matrix have potential to offer scientific and technological advantages, since the organized two-dimensional arrays of organic species between the interlayers can result in novel functions that are different to the typical functions of the individual organic species [18–23].
http://dx.doi.org/10.1016/j.jiec.2014.06.025 1226-086X/ß 2014 Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering Chemistry.
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The intercalation of organic anions such as carboxylate groups is an important aspect of layered double hydroxide (LDH) for further research into the development of interesting properties and potential application in the fields such as polymer/LDH nanocomposites [24–27] and drug delivery [28,29]. The intercalation of some short length chain fatty acids into different kinds of LDHs has been investigated [30]. However, apparently there is no report of comparison the intercalation capacity of the stearate anions into the Mg3Al LDH and Zn3Al LDH. In this study Mg3Al LDH and Zn3Al LDH matrices have been used for the intercalation of stearate anions to study the effect of divalent metal on the properties of pristine and modified LDHs.
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Materials and methods
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Materials
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Magnesium nitrate hexahydrate and aluminum nitrate nonahydrate were supplied by HmbG, Germany. Zinc nitrate hexahydrate was purchased from Bendosen Laboratory Chemicals, Malaysia. Sodium hydroxide pellets was obtained from Merck, Germany. Sodium stearate was purchased from R & M chemicals, U.K. Chloroform was purchased from Merck, Germany and polylactide resin 4042D was supplied by Nature Works LLC, U.S.A. All the above commercial chemicals were used as received.
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Synthesis of Mg3Al LDH
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The pristine Mg3Al LDH with NO3- as interlayer anion was prepared by first adding dropwise an aqueous solution of NaOH (1 M) into a 250 ml solution containing exactly weighted of 19.22 g Mg(NO3)26H2O and 9.38 g Al(NO3)39H2O (with the mol ratio of 3– 1 respectively) until pH 9 was obtained. During the co-precipitation process, nitrogen gas was bubbled throughout the reaction system to minimize the presence of CO32 in the solution. The resulting suspension was then shaken at 100 rpm and 70 8C for 16 h. The slurry was filtered, washed thoroughly with deionized water and then dried at 60 8C to obtain the Mg3Al LDH. The final product was ground and sieved using sieve to particles of less than 100 mm.
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Synthesis of Zn3Al LDH
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The original Zn3Al LDH with NO3- as interlayer anion was prepared by the same process of the synthesis of Mg3Al LDH. The details were as followed: 22.30 g Zn(NO3)26H2O and 9.38 g Al(NO3)39H2O were dissolved into 250 ml deionized water. The pH of the solution was adjusted by dropwise addition of 1 M aqueous solution of NaOH under the nitrogen environment until pH 7.0 was obtained. After shaking of the resulting suspension at 100 rpm at 70 8C for 16 h, the precipitate formed was collected and washed with deionized water and then dried at 60 8C to obtain the original Zn3Al LDH. The final product was ground and sieved using sieve with pore size of 100 mm.
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Preparation of stearate-Mg3Al LDH and stearate-Zn3Al LDH
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The stearate-modified LDHs were prepared by replacing the nitrate ions existing in the interlayers of the LDHs with stearate ions via ion exchange reaction using the following procedure. Exactly weighted of the dry Mg3Al LDH or Zn3Al LDH (1.00 g) was first transferred into 750 ml of a 0.003 M solution of sodium stearate and stirred for 24 h at room temperature for Mg3Al LDH, while for Zn3Al LDH the temperature was adjusted to 70 8C. The white solid obtained was then filtered, washed with deionized
water three times and dried in a vacuum desiccator at room temperature.
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Characterization techniques
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X-ray diffraction (XRD) patterns of the LDHs and composites were recorded using a Shidmadzu XRD 6000 Diffractometer at 30 kV and 30 mA with Cu-Ka radiation of the wavelength of 1.5405 nm in 2u range from 2 to 508. Fourier transform infrared (FTIR) spectra of the materials were recorded on a Perkin Elmer, FTI 1650 Spectrum BX, England Spectrometer. Spectra were recorded from 400 to 4000 cm1 using a KBr disk method. Scanning electron microscopy (SEM) images were obtained using a Philips XL30 environmental scanning electron microscope. The clean and dry samples were first coated with gold using a Bal-Tec SCD 005 sputter coater. The transmission electron microscopy (TEM) images were obtained by employing a transmission electron microscope Hitachi, H7100 with an accelerating voltage of 200 kV. The samples were dispersed in chloroform and diluted to the right concentration. The suspension was then dropped on to the TEM sample grid and allowed it to dry. The very thin layer on the grid was observed on the microscope. The percentage of carbon (C), hydrogen (H) and nitrogen (N) in the pristine and modified LDHs was determined by a LECO Corporation CHNS-932 Elemental Analyzer. The thermogravimetric analysis (TGA) of the samples was carried out by a Perkin Elmer Thermobalance TGA7. The samples were studied under a nitrogen gas atmosphere with a flow of 20 cm3 min1 using a scan rate of 10 8C min1.
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Results and discussion
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Characterization of Mg3Al LDH, Zn3Al LDH, stearate-Mg3Al LDH and stearate-Zn3Al LDH
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The XRD patterns in the range of 2u from 2 to 508 for the pristine and modified LDHs are shown in Figs. 1 and 2. It is apparent that both LDH and stearate-Mg3Al LDH are crystalline in nature with well-defined layered structure. The basal spacing (d) of the LDHs or stearate-LDHs is calculated from the first diffraction peak using Bragg’s equation, nl = 2d sin u, where n is equal to 1 for the h0 0 3i peak, l is the wave length of Cu-Ka radiation, and u is the half of the scattering angle. The intercalation of the stearate anions is clearly seen in each case by the significant increase in basal spacing (Table 1) compared with that in the nitrate precursor [31]. From the comparison of the basal spacing of stearate-Mg3Al LDH and stearate-Zn3Al LDH, it is apparent that the increment of the basal spacing in stearate-Zn3Al LDH is clearly more than that of
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Fig. 1. XRD pattern of (a) pristine Mg3Al LDH and (b) stearate-Mg3Al LDH.
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Fig. 2. XRD pattern of pristine Zn3Al LDH and stearate-Zn3Al LDH. Fig. 4. FTIR spectra for pristine Zn3Al LDH and stearate-Zn3Al LDH. Table 1 Basal spacing of LDHs and stearate-LDHs. LDH
2u (8)
Basal spacing (A˚)
Mg3Al LDH Stearate-Mg3Al LDH Zn3Al LDH Stearate-Zn3Al LDH
10.14 2.78 10.00 2.156
8.72 31.68 8.83 40.10
Fig. 3. FTIR spectra for pristine Mg3Al LDH and stearate-Mg3Al LDH.
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stearate-Mg3Al LDH might be related to the more intercalation of stearate anions between its layers. Figs. 3 and 4 show the FT-IR spectra of the original and modified LDHs. The original LDHs have a broad adsorption band at around 3500 cm1 due to O–H group stretching of both hydroxide layers and interlayer water molecules. The stretching vibration (H–OH) of the interlayer water can be observed at about 1600–1650 cm1. The lattice vibration bands of the M–O and O–M–O (M = Mg, Zn or Al) bondings appear at below 800 cm1 region. The pristine LDHs also show an intense band at 1384 cm1 which can be associated with the asymmetric stretching vibration of the nitrate anions [32]. Meanwhile the stearate-Mg3Al LDH and stearate-Zn3Al LDH spectra show absorption bands at 2800–3000 cm1 (Figs. 3(b) and 4(b)), which are the characteristic adsorptions of the C–H stretching vibration due to the presence of the –CH3 and –CH2 groups of long chain stearate anions [20]. It also indicates two strong absorption peaks of the carboxylate asymmetric and symmetric stretching are at around 1532 and 1398 cm1, respectively [12].
Table 2 The carbon, nitrogen and hydrogen content of pristine and modified LDHs. LDH
%C
%N
%H
Mg3Al LDH Stearate-Mg3Al LDH Zn3Al LDH Stearate-Zn3Al LDH
0.00 36.520 0.00 41.058
3.559 1.175 2.209 0.000
3.588 6.933 2.384 7.658
Surface morphology of the pristine and modified stearate-LDH particles is shown in Figs. 5 and 6. As shown by the figures, the clays are obtained as porous particles in the presence of the organic anions. Table 2 shows the weight percentage of carbon, nitrogen and hydrogen in the pristine and modified LDHs obtained by elemental analysis. Th replacement of nitrate anion in LDHs with the stearate anion causes the number of nitrogen content in the modified LDHs to decrease. The increase of the carbon content confirmed the presence of the stearate anions in the modified LDHs. The percentage of carbon in stearate-Zn3Al LDH is 5.538% more than the amount of carbon in stearate-Mg3Al LDH, this shows that the ion exchange capacity of Zn3Al LDH for stearate ions are higher than that of Mg3Al LDH. The calculated amount of stearate anions in the modified LDHs were found to be 169.07 mmol stearate/100 g Mg3Al LDH and 190.08 mmol stearate/100 g Zn3Al LDH based on carbon. The thermogravimetric analysis (TGA) and differential thermogravimetric (DTG) thermograms for pristine and modified stearate-LDH particles are shown in Figs. 7 and 8. A two-stage decomposition process can be considered for thermal decomposition of unmodified LDHs. The first step below about 225 8C is related to removal of adsorbed and elimination of the interlayer water. The next decomposition stage occurs around 225–500 8C that is due to the loss of interlayer nitrate and dehydroxylation of the metal hydroxide layer. During this stage the hydroxide layers are decomposed into metal oxide and water vapor [33–35]. However the second stage decomposition for Mg3Al LDH appear at around 1808 higher than that of Zn3Al LDH (Figs. 7 and 8), which resemble to the more thermally stability of Mg3Al LDH, because The rate of dehydroxylation has been used as a measure of the thermal stability of the hydrotalcite structure, where a delay in dehydroxylation indicates a more thermally stable hydrotalcite [35]. In the modified LDHs, the presence of the stearate anions influence the thermal behavior of the samples significantly, especially the second stage of the decomposition process, which
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Fig. 5. Scanning electron micrographs of (a) Mg3Al LDH and (b) stearate-Mg3Al LDH.
Fig. 6. Scanning electron micrographs of (a) Zn3Al LDH and (b) stearate-Zn3Al LDH.
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leads to a complete collapse of the structure [33]. The weight loss up to about 225 8C of the modified samples is due to the loss of interlayer water that is comparable to the unmodified LDH and the second stage of the decomposition process is attributed to the decomposition of the stearate anions and also the loss of the remaining nitrate and dehydroxylation of the host layers. A comparison of Figs. 7 and 8 shows that stearate-Zn3Al LDH is suffering much more weight loss relative to its original LDH (around 29.84) compared to the stearate-Mg3Al LDH (around 23.38). This indicates that in stearate-Zn3Al LDH much more
stearate anions are accommodated in the interlayer region, which is also reflected in by the basal spacing and elemental analysis as discussed above. The ability of Zn3Al LDH to accommodate more stearate anions compared to the Mg3Al LDH may be attributed to the larger ionic radius of zinc. The ionic radius of magnesium (0.65 A˚) is smaller than zinc (0.74 A˚) and hence its charge density is larger [36]. The higher charge density makes it more difficult to separate the layers and intercalation of stearate anions. The TEM images of the pristine and modified LDHs are shown in Figs. 9–12. It can be seen that unmodified LDHs have large
Fig. 7. (a) TGA and (b) DTG thermograms of Mg3Al LDH and stearate-Mg3Al LDH.
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Fig. 8. (a) TGA and (b) DTG thermograms of Zn3Al LDH and stearate-Zn3Al LDH.
Fig. 9. TEM images of Mg3Al LDH at different magnifications.
Fig. 10. TEM images of stearate-Mg3Al LDH at different magnifications.
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Fig. 11. TEM images of Zn3Al LDH at different magnifications.
Fig. 12. TEM images of stearate-Zn3Al LDH at different magnifications.
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agglomerated of clay platelets with a branchy structure while both stearate-Mg3Al LDH and stearate-Zn3Al LDH show expanded thin layers caused by the stearate intercalation into the interlayer space of LDHs. Although there are morphological changes due to the interlayer expansion, the layered structure is preserved perfectly [37]. A comparison of Figs. 9 and 12 shows that the expansion of layers in stearate-Zn3Al LDH is larger related to stearate-Mg3Al LDH which is in good accordance to the basal spacing of 31.68 A˚ for stearate-Mg3Al LDH and 40.1 A˚ in stearate-Zn3Al LDH obtained from XRD analysis [37].
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Conclusions
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Anionic clays Mg3Al LDH and Zn3Al LDH were firstly prepared by a co-precipitation method from nitrate salts solution and then modified by stearate anions through an ion exchange reaction. The successful incorporation of the stearate anions was confirmed by increasing in d003 basal spacing of the obtained products in comparison with Mg3Al LDH and Zn3Al LDH precursors. The presence of the stearate ions in the organomodified LDHs was confirmed by FTIR spectra of the organoclays. The TGA showed that decomposition process of LDHs occurs during different stages. A
comparison of decomposition thermograms of modified LDHs showed that stearate-Zn3Al LDH is suffering much more weight loss relative to its original LDH (around 29.84%) compared to the stearate-Mg3Al LDH (around 23.38%). This might be indicates that in stearate-Zn3Al LDH much more stearate anions are accommodated in the interlayer region, which is also reflected in by the basal spacing and elemental analysis. SEM micrograph revealed the presence of stearate anions in the interlayer changed the compact and massive curve plates of the LDHs into porous particles. The amount of stearate anions present in stearate-Mg3Al LDH and stearate-Zn3Al LDH were 169.07 and 190.08 mmol/100 g, respectively, as shown by CHNS elemental analysis. The TEM images of pristine and modified LDHs showed that the layers of Mg3Al LDH and Zn3Al LDH were separated after the modification process because of intercalation of stearate anions into the interlayer space of unmodified LDHs.
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Acknowledgment
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The authors thank the staff at the Institute of Bioscience Universiti Putra Malaysia for their support with SEM and TEM instruments.
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References
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[1] E. Li, Z.P. Xu, V. Rudolph, Appl. Catal. B 88 (2009) 42–49. [2] E. Coronado, C. Martı´-Gastaldo, E. Navarro-Moratalla, A. Ribera, Appl. Clay Sci. 48 (2009) 228–234. [3] K.S. Triantafyllidis, E.N. Peleka, V.G. Komvokis, P.P. Mavros, J. Colloid Interface Sci. 342 (2009) 427–436. [4] B. Schwenzer, J.R. Neilson, K. Sivula, C. Woo, J.M.J. Fre´chet, D.E. Morse, Thin Solid Films 517 (2009) 5722–5727. [5] R. Rojas Delgado, M. Arandigoyen Vidaurre, C.P. De Pauli, M.A. Ulibarri, M.J. Avena, J. Colloid Interface Sci. 280 (2004) 431–441. [6] L.F. Da Silva, J. Tronto, H.P. Oliveira, J.B. Valim, J. Incl. Phenom. Macrocycl. Chem. 46 (2003) 187–193. [7] C. Forano, T. Hibino, F. Leroux, C. Taviot-Gue´ho, Dev. Clay Sci. 1 (2006) 1021–1095. [8] F.B.D. Saiah, B.L. Su, N. Bettahar, J. Hazard. Mater. 165 (2009) 206–217. [9] K.A. Carrado, A. Kostapapas, S.L. Suib, Solid State Ionics 26 (1988) 77–86. [10] R.V. Prikhod’ko, M.V. Sychev, I.M. Astrelin, K. Erdmann, A. Mangel, R.A. Van Santen, Russ. J. Appl. Chem. 74 (2001) 1621–1626. [11] M. Eili, K. Shameli, N.A. Ibrahim, W.M.Z. Wan Yunus, Int. J. Mol. Sci. 13 (2012) 7938–7951. [12] H.B. Hsueh, C.Y. Chen, Polymer 44 (2003) 1151–1161. [13] L.P. Cardoso, J.B. Valim, J. Phys. Chem. Solids 67 (2006) 987–993. [14] C.Mousty, O.Kaftan,V.Prevot,C.Forano,Sens.ActuatorsB:Chem.133(2008)442–448. [15] J. Das, B. Sairam Patra, N. Baliarsingh, K.M. Parida, J. Colloid Interface Sci. 316 (2007) 216–223. [16] C. Manzi-Nshuti, P. Songtipya, E. Manias, M.M. Jimenez-Gasco, J.M. Hossenlopp, C.A. Wilkie, Polymer 50 (2009) 3564–3574. [17] G.S. Thomas, P.V. Kamath, Solid State Sci. 8 (2006) 1181–1186. [18] K. Shameli, M.B. Ahmad, S.D. Jazayeri, P. Shabanzadeh, P. Sangpour, H. Jahangirian, Chem. Cent. J. 6 (1) (2012) 1–10.
7
[19] Y.L. Pak, M.B. Ahmad, K. Shameli, W.M.Z. Wan Yunus, N.A. Ibrahim, N. Zainuddin, J. 299 Nanomater. (2013) 1–9. , http://dx.doi.org/10.1155/2013/621097. 300 [20] M.B. Ahmad, J.J. Lim, K. Shameli, N.A. Ibrahim, M.Y. Tay, B.W. Chieng, Chem. Cent. 301 J. 6 (1) (2012) 1–9. 302 [21] M.B. Ahmad, J.J. Lim, K. Shameli, N.A. Ibrahim, M.Y. Tay, Molecules 16 (9) (2011) 303 7237–7248. 304 [22] Y.L. Pak, M.B. Ahmad, K. Shameli, W.M.Z. Wan Yunus, N.A. Ibrahim, N. Zainuddin, 305 Dig. J. Nanomater. Biostruct. 8 (4) (2013) 1395–1403. 306 [23] C.P. Liau, M.B. Ahmad, K. Shameli, W.M.Z. Wan Yunus, N.A. Ibrahim, N. Zainuddin, 307 Y.Y. Then, Sci. World J. (2013) 1–22 (in press). Q2308 [24] D. Basu, A. Das, K.W. Stockelhuber, U. Wagenknecht, G. Heinrich, Prog. Polym. Sci. 309 (2013) 1–33. , http://dx.doi.org/10.1016/j.progpolymsci.2013.07.011. 310 [25] Y. Kameshima, H. Yoshizaki, A. Nakajima, K. Okada, J. Colloid Interface Sci. 298 311 (2006) 624–628. 312 [26] J. Liu, G. Chen, J. Yang, Polymer 49 (2008) 3923–3927. 313 [27] Z.P. Xu, P.S. Braterman, Appl. Clay Sci. 48 (2009) 235–242. 314 [28] M.L. Hans, A.M. Lowman, Curr. Opin. Solid State Mater. Sci. 6 (2002) 319–327. 315 [29] M.J.S. Ortega, T. Stauner, B. Loretz, J.L. Ortega-Vinuesa, D. Bastos-Gonza´lez, G. 316 Wenz, U.F. Schaefer, C.M. Lehr, J. Control. Release 141 (2010) 85–92. 317 [30] J. Zhang, F. Zhang, L. Ren, D.G. Evans, X. Duan, Mater. Chem. Phys. 85 (2004) 318 207–214. 319 [31] S. Pradhan, F.R. Costa, U. Wagenknecht, D. Jehnichen, A.K. Bhowmick, G. Heinrich, 320 Eur. Polym. J. 44 (2008) 3122–3132. 321 [32] Y. Ding, Z. Gui, J. Zhu, Y. Hu, Z. Wang, Mater. Res. Bull. 43 (2008) 3212–3220. 322 [33] F.R. Costa, A. Leuteritz, U. Wagenknecht, D. Jehnichen, L. Ha¨ußler, G. Heinrich, 323 Appl. Clay Sci. 38 (2008) 153–164. 324 [34] Z. Ni, F. Xing, P. Wang, G. Cao, Appl. Clay Sci. 40 (2008) 72–80. 325 [35] S.J. Palmer, R.L. Frost, T. Nguyen, Coord. Chem. Rev. 253 (2009) 250–267. 326 [36] F. Cavani, F. Trifiro`, A. Vaccari, Catal. Today 11 (1991) 173–301. 327 [37] J. Plank, Z. Dai, P.R. Andres, Mater. Lett. 60 (2006) 3614–3617. 328
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JIEC 2101 1–7 Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx
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The effect of the divalent metal on the intercalation capacity of stearate anions into layered double hydroxide nanolayers Eili a,*, Kamyar Shameli b,**, Nor Azowa Ibrahim b, Mansor Bin Ahmad b, Wan Md Zin Wan Yunus c
Q1 Mahboobeh
a
Faculty of Basic Sciences and Advanced Technologies, University of Science and Culture, Park Avenue, Ashrafi Esfahani Boulevard, Tehran IR14536-33143, Iran b Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Serdang, Selangor 43400, Malaysia c Department of Chemistry, Centre for Defence Foundation Studies, National Defence University of Malaysia, Kuala Lumpur 57000, Malaysia
A R T I C L E I N F O
A B S T R A C T
Article history: Received 21 February 2014 Accepted 16 June 2014 Available online xxx
A comparison has been made of the intercalation capacity of the stearate anions into the two different anionic clays: magnesium aluminum layered double hydroxide (Mg3Al LDH) and zinc aluminum layered double hydroxide (Zn3Al LDH). The anionic clays Mg3Al LDH and Zn3Al LDH were firstly prepared by coprecipitation method from nitrate salts solution and then modified by stearate anions through an ion exchange reaction. The properties, morphologies and ion exchange ability of these two clays have been studied by XRD, TGA, SEM, TEM and CHNS that show the ability of Zn3Al LDH to capture stearate anions is greater than Mg3Al LDH. ß 2014 Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering Chemistry.
Keywords: Layered double hydroxide Comparison Intercalation capacity Elemental analysis Thermogravimetric analysis
10 11
Introduction
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Layered structure solids are very useful materials because of their wide potential applications in different fields such as catalysts [1], ion exchangers [2], sorbents [3], and electrochemistry [4]. They can divided into different groups, taking into account the charge excess within the layers, include negatively charged layers solids like montmorillonite, positively charged layers solids like layered double hydroxide (LDH) and neutrally charged layers such as mica and graphite [5]. Among these materials both phyllosilicate clays and LDHs have attracted an increasing amount of attention due to the presence of electrical charges within the layers and therefore their capability to ion-exchange that is an important property for different applications. However, LDHs present certain specific advantages, which are lacking in layered silicates type nanoclays such as their relative ease and low cost of synthesis, thermal and chemical stability, surface properties, nontoxicity, adjustability of their particle size and aspect ratio by changing the reaction conditions and the wide range of choice for surfactants like fatty acid salts, sulfonates,
* Corresponding author. ** Corresponding author. Tel.: +60 3 8946 6775; fax: +60 3 8943 5380. E-mail addresses: [email protected] (M. Eili), [email protected] (K. Shameli).
sulfates, phosphates, etc., that can intercalated between the layers for extensive applications in different fields [6–8]. Layered double hydroxides (LDHs) are anionic clays which can X be represented as ½MðIIÞ1X MðIIIÞX ðOHÞ2 Xþ ½An where X=n mH2 O M(II) and M(III) are divalent and trivalent cations, respectively, and An is an exchangeable anion [9,10]. LDHs are composed of octahedral M2+(OH)6 brucite-like layers which are positively charged by the partial substitution of M3+ for M2+. Thus, anions are intercalated into the interlayers in order to compensate the positive layer charges [11,12]. Every M(II) and M(III) ions which have similar ionic radius to accommodate in the holes of the close packed configuration of OH groups in the brucite-like layers can form LDH but depend on the nature of cations, the obtained LDH can have different physical characteristics such as surface basicity and ion exchange capacity [13,14]. LDHs with different cations, such as Mg, Mn, Fe, Co, Ni, Cu, and Zn for divalent cations and Al, Mn, Fe, Co, Ni, Cr, and Ga for trivalent cations have been studied, however, the most reported have been focused on using MgAl LDH and ZnAl LDH, since zinc, magnesium and aluminum yield more environmentally friendly materials [8,15–17]. Inorganic–organic nanocomposite materials with functional organic compounds immobilized into a layered inorganic matrix have potential to offer scientific and technological advantages, since the organized two-dimensional arrays of organic species between the interlayers can result in novel functions that are different to the typical functions of the individual organic species [18–23].
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The intercalation of organic anions such as carboxylate groups is an important aspect of layered double hydroxide (LDH) for further research into the development of interesting properties and potential application in the fields such as polymer/LDH nanocomposites [24–27] and drug delivery [28,29]. The intercalation of some short length chain fatty acids into different kinds of LDHs has been investigated [30]. However, apparently there is no report of comparison the intercalation capacity of the stearate anions into the Mg3Al LDH and Zn3Al LDH. In this study Mg3Al LDH and Zn3Al LDH matrices have been used for the intercalation of stearate anions to study the effect of divalent metal on the properties of pristine and modified LDHs.
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Materials and methods
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Materials
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Magnesium nitrate hexahydrate and aluminum nitrate nonahydrate were supplied by HmbG, Germany. Zinc nitrate hexahydrate was purchased from Bendosen Laboratory Chemicals, Malaysia. Sodium hydroxide pellets was obtained from Merck, Germany. Sodium stearate was purchased from R & M chemicals, U.K. Chloroform was purchased from Merck, Germany and polylactide resin 4042D was supplied by Nature Works LLC, U.S.A. All the above commercial chemicals were used as received.
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Synthesis of Mg3Al LDH
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The pristine Mg3Al LDH with NO3- as interlayer anion was prepared by first adding dropwise an aqueous solution of NaOH (1 M) into a 250 ml solution containing exactly weighted of 19.22 g Mg(NO3)26H2O and 9.38 g Al(NO3)39H2O (with the mol ratio of 3– 1 respectively) until pH 9 was obtained. During the co-precipitation process, nitrogen gas was bubbled throughout the reaction system to minimize the presence of CO32 in the solution. The resulting suspension was then shaken at 100 rpm and 70 8C for 16 h. The slurry was filtered, washed thoroughly with deionized water and then dried at 60 8C to obtain the Mg3Al LDH. The final product was ground and sieved using sieve to particles of less than 100 mm.
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Synthesis of Zn3Al LDH
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The original Zn3Al LDH with NO3- as interlayer anion was prepared by the same process of the synthesis of Mg3Al LDH. The details were as followed: 22.30 g Zn(NO3)26H2O and 9.38 g Al(NO3)39H2O were dissolved into 250 ml deionized water. The pH of the solution was adjusted by dropwise addition of 1 M aqueous solution of NaOH under the nitrogen environment until pH 7.0 was obtained. After shaking of the resulting suspension at 100 rpm at 70 8C for 16 h, the precipitate formed was collected and washed with deionized water and then dried at 60 8C to obtain the original Zn3Al LDH. The final product was ground and sieved using sieve with pore size of 100 mm.
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Preparation of stearate-Mg3Al LDH and stearate-Zn3Al LDH
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The stearate-modified LDHs were prepared by replacing the nitrate ions existing in the interlayers of the LDHs with stearate ions via ion exchange reaction using the following procedure. Exactly weighted of the dry Mg3Al LDH or Zn3Al LDH (1.00 g) was first transferred into 750 ml of a 0.003 M solution of sodium stearate and stirred for 24 h at room temperature for Mg3Al LDH, while for Zn3Al LDH the temperature was adjusted to 70 8C. The white solid obtained was then filtered, washed with deionized
water three times and dried in a vacuum desiccator at room temperature.
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Characterization techniques
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X-ray diffraction (XRD) patterns of the LDHs and composites were recorded using a Shidmadzu XRD 6000 Diffractometer at 30 kV and 30 mA with Cu-Ka radiation of the wavelength of 1.5405 nm in 2u range from 2 to 508. Fourier transform infrared (FTIR) spectra of the materials were recorded on a Perkin Elmer, FTI 1650 Spectrum BX, England Spectrometer. Spectra were recorded from 400 to 4000 cm1 using a KBr disk method. Scanning electron microscopy (SEM) images were obtained using a Philips XL30 environmental scanning electron microscope. The clean and dry samples were first coated with gold using a Bal-Tec SCD 005 sputter coater. The transmission electron microscopy (TEM) images were obtained by employing a transmission electron microscope Hitachi, H7100 with an accelerating voltage of 200 kV. The samples were dispersed in chloroform and diluted to the right concentration. The suspension was then dropped on to the TEM sample grid and allowed it to dry. The very thin layer on the grid was observed on the microscope. The percentage of carbon (C), hydrogen (H) and nitrogen (N) in the pristine and modified LDHs was determined by a LECO Corporation CHNS-932 Elemental Analyzer. The thermogravimetric analysis (TGA) of the samples was carried out by a Perkin Elmer Thermobalance TGA7. The samples were studied under a nitrogen gas atmosphere with a flow of 20 cm3 min1 using a scan rate of 10 8C min1.
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Results and discussion
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Characterization of Mg3Al LDH, Zn3Al LDH, stearate-Mg3Al LDH and stearate-Zn3Al LDH
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The XRD patterns in the range of 2u from 2 to 508 for the pristine and modified LDHs are shown in Figs. 1 and 2. It is apparent that both LDH and stearate-Mg3Al LDH are crystalline in nature with well-defined layered structure. The basal spacing (d) of the LDHs or stearate-LDHs is calculated from the first diffraction peak using Bragg’s equation, nl = 2d sin u, where n is equal to 1 for the h0 0 3i peak, l is the wave length of Cu-Ka radiation, and u is the half of the scattering angle. The intercalation of the stearate anions is clearly seen in each case by the significant increase in basal spacing (Table 1) compared with that in the nitrate precursor [31]. From the comparison of the basal spacing of stearate-Mg3Al LDH and stearate-Zn3Al LDH, it is apparent that the increment of the basal spacing in stearate-Zn3Al LDH is clearly more than that of
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Fig. 1. XRD pattern of (a) pristine Mg3Al LDH and (b) stearate-Mg3Al LDH.
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Fig. 2. XRD pattern of pristine Zn3Al LDH and stearate-Zn3Al LDH. Fig. 4. FTIR spectra for pristine Zn3Al LDH and stearate-Zn3Al LDH. Table 1 Basal spacing of LDHs and stearate-LDHs. LDH
2u (8)
Basal spacing (A˚)
Mg3Al LDH Stearate-Mg3Al LDH Zn3Al LDH Stearate-Zn3Al LDH
10.14 2.78 10.00 2.156
8.72 31.68 8.83 40.10
Fig. 3. FTIR spectra for pristine Mg3Al LDH and stearate-Mg3Al LDH.
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stearate-Mg3Al LDH might be related to the more intercalation of stearate anions between its layers. Figs. 3 and 4 show the FT-IR spectra of the original and modified LDHs. The original LDHs have a broad adsorption band at around 3500 cm1 due to O–H group stretching of both hydroxide layers and interlayer water molecules. The stretching vibration (H–OH) of the interlayer water can be observed at about 1600–1650 cm1. The lattice vibration bands of the M–O and O–M–O (M = Mg, Zn or Al) bondings appear at below 800 cm1 region. The pristine LDHs also show an intense band at 1384 cm1 which can be associated with the asymmetric stretching vibration of the nitrate anions [32]. Meanwhile the stearate-Mg3Al LDH and stearate-Zn3Al LDH spectra show absorption bands at 2800–3000 cm1 (Figs. 3(b) and 4(b)), which are the characteristic adsorptions of the C–H stretching vibration due to the presence of the –CH3 and –CH2 groups of long chain stearate anions [20]. It also indicates two strong absorption peaks of the carboxylate asymmetric and symmetric stretching are at around 1532 and 1398 cm1, respectively [12].
Table 2 The carbon, nitrogen and hydrogen content of pristine and modified LDHs. LDH
%C
%N
%H
Mg3Al LDH Stearate-Mg3Al LDH Zn3Al LDH Stearate-Zn3Al LDH
0.00 36.520 0.00 41.058
3.559 1.175 2.209 0.000
3.588 6.933 2.384 7.658
Surface morphology of the pristine and modified stearate-LDH particles is shown in Figs. 5 and 6. As shown by the figures, the clays are obtained as porous particles in the presence of the organic anions. Table 2 shows the weight percentage of carbon, nitrogen and hydrogen in the pristine and modified LDHs obtained by elemental analysis. Th replacement of nitrate anion in LDHs with the stearate anion causes the number of nitrogen content in the modified LDHs to decrease. The increase of the carbon content confirmed the presence of the stearate anions in the modified LDHs. The percentage of carbon in stearate-Zn3Al LDH is 5.538% more than the amount of carbon in stearate-Mg3Al LDH, this shows that the ion exchange capacity of Zn3Al LDH for stearate ions are higher than that of Mg3Al LDH. The calculated amount of stearate anions in the modified LDHs were found to be 169.07 mmol stearate/100 g Mg3Al LDH and 190.08 mmol stearate/100 g Zn3Al LDH based on carbon. The thermogravimetric analysis (TGA) and differential thermogravimetric (DTG) thermograms for pristine and modified stearate-LDH particles are shown in Figs. 7 and 8. A two-stage decomposition process can be considered for thermal decomposition of unmodified LDHs. The first step below about 225 8C is related to removal of adsorbed and elimination of the interlayer water. The next decomposition stage occurs around 225–500 8C that is due to the loss of interlayer nitrate and dehydroxylation of the metal hydroxide layer. During this stage the hydroxide layers are decomposed into metal oxide and water vapor [33–35]. However the second stage decomposition for Mg3Al LDH appear at around 1808 higher than that of Zn3Al LDH (Figs. 7 and 8), which resemble to the more thermally stability of Mg3Al LDH, because The rate of dehydroxylation has been used as a measure of the thermal stability of the hydrotalcite structure, where a delay in dehydroxylation indicates a more thermally stable hydrotalcite [35]. In the modified LDHs, the presence of the stearate anions influence the thermal behavior of the samples significantly, especially the second stage of the decomposition process, which
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Fig. 5. Scanning electron micrographs of (a) Mg3Al LDH and (b) stearate-Mg3Al LDH.
Fig. 6. Scanning electron micrographs of (a) Zn3Al LDH and (b) stearate-Zn3Al LDH.
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leads to a complete collapse of the structure [33]. The weight loss up to about 225 8C of the modified samples is due to the loss of interlayer water that is comparable to the unmodified LDH and the second stage of the decomposition process is attributed to the decomposition of the stearate anions and also the loss of the remaining nitrate and dehydroxylation of the host layers. A comparison of Figs. 7 and 8 shows that stearate-Zn3Al LDH is suffering much more weight loss relative to its original LDH (around 29.84) compared to the stearate-Mg3Al LDH (around 23.38). This indicates that in stearate-Zn3Al LDH much more
stearate anions are accommodated in the interlayer region, which is also reflected in by the basal spacing and elemental analysis as discussed above. The ability of Zn3Al LDH to accommodate more stearate anions compared to the Mg3Al LDH may be attributed to the larger ionic radius of zinc. The ionic radius of magnesium (0.65 A˚) is smaller than zinc (0.74 A˚) and hence its charge density is larger [36]. The higher charge density makes it more difficult to separate the layers and intercalation of stearate anions. The TEM images of the pristine and modified LDHs are shown in Figs. 9–12. It can be seen that unmodified LDHs have large
Fig. 7. (a) TGA and (b) DTG thermograms of Mg3Al LDH and stearate-Mg3Al LDH.
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Fig. 8. (a) TGA and (b) DTG thermograms of Zn3Al LDH and stearate-Zn3Al LDH.
Fig. 9. TEM images of Mg3Al LDH at different magnifications.
Fig. 10. TEM images of stearate-Mg3Al LDH at different magnifications.
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Fig. 11. TEM images of Zn3Al LDH at different magnifications.
Fig. 12. TEM images of stearate-Zn3Al LDH at different magnifications.
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agglomerated of clay platelets with a branchy structure while both stearate-Mg3Al LDH and stearate-Zn3Al LDH show expanded thin layers caused by the stearate intercalation into the interlayer space of LDHs. Although there are morphological changes due to the interlayer expansion, the layered structure is preserved perfectly [37]. A comparison of Figs. 9 and 12 shows that the expansion of layers in stearate-Zn3Al LDH is larger related to stearate-Mg3Al LDH which is in good accordance to the basal spacing of 31.68 A˚ for stearate-Mg3Al LDH and 40.1 A˚ in stearate-Zn3Al LDH obtained from XRD analysis [37].
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Conclusions
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Anionic clays Mg3Al LDH and Zn3Al LDH were firstly prepared by a co-precipitation method from nitrate salts solution and then modified by stearate anions through an ion exchange reaction. The successful incorporation of the stearate anions was confirmed by increasing in d003 basal spacing of the obtained products in comparison with Mg3Al LDH and Zn3Al LDH precursors. The presence of the stearate ions in the organomodified LDHs was confirmed by FTIR spectra of the organoclays. The TGA showed that decomposition process of LDHs occurs during different stages. A
comparison of decomposition thermograms of modified LDHs showed that stearate-Zn3Al LDH is suffering much more weight loss relative to its original LDH (around 29.84%) compared to the stearate-Mg3Al LDH (around 23.38%). This might be indicates that in stearate-Zn3Al LDH much more stearate anions are accommodated in the interlayer region, which is also reflected in by the basal spacing and elemental analysis. SEM micrograph revealed the presence of stearate anions in the interlayer changed the compact and massive curve plates of the LDHs into porous particles. The amount of stearate anions present in stearate-Mg3Al LDH and stearate-Zn3Al LDH were 169.07 and 190.08 mmol/100 g, respectively, as shown by CHNS elemental analysis. The TEM images of pristine and modified LDHs showed that the layers of Mg3Al LDH and Zn3Al LDH were separated after the modification process because of intercalation of stearate anions into the interlayer space of unmodified LDHs.
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Acknowledgment
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The authors thank the staff at the Institute of Bioscience Universiti Putra Malaysia for their support with SEM and TEM instruments.
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References
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[1] E. Li, Z.P. Xu, V. Rudolph, Appl. Catal. B 88 (2009) 42–49. [2] E. Coronado, C. Martı´-Gastaldo, E. Navarro-Moratalla, A. Ribera, Appl. Clay Sci. 48 (2009) 228–234. [3] K.S. Triantafyllidis, E.N. Peleka, V.G. Komvokis, P.P. Mavros, J. Colloid Interface Sci. 342 (2009) 427–436. [4] B. Schwenzer, J.R. Neilson, K. Sivula, C. Woo, J.M.J. Fre´chet, D.E. Morse, Thin Solid Films 517 (2009) 5722–5727. [5] R. Rojas Delgado, M. Arandigoyen Vidaurre, C.P. De Pauli, M.A. Ulibarri, M.J. Avena, J. Colloid Interface Sci. 280 (2004) 431–441. [6] L.F. Da Silva, J. Tronto, H.P. Oliveira, J.B. Valim, J. Incl. Phenom. Macrocycl. Chem. 46 (2003) 187–193. [7] C. Forano, T. Hibino, F. Leroux, C. Taviot-Gue´ho, Dev. Clay Sci. 1 (2006) 1021–1095. [8] F.B.D. Saiah, B.L. Su, N. Bettahar, J. Hazard. Mater. 165 (2009) 206–217. [9] K.A. Carrado, A. Kostapapas, S.L. Suib, Solid State Ionics 26 (1988) 77–86. [10] R.V. Prikhod’ko, M.V. Sychev, I.M. Astrelin, K. Erdmann, A. Mangel, R.A. Van Santen, Russ. J. Appl. Chem. 74 (2001) 1621–1626. [11] M. Eili, K. Shameli, N.A. Ibrahim, W.M.Z. Wan Yunus, Int. J. Mol. Sci. 13 (2012) 7938–7951. [12] H.B. Hsueh, C.Y. Chen, Polymer 44 (2003) 1151–1161. [13] L.P. Cardoso, J.B. Valim, J. Phys. Chem. Solids 67 (2006) 987–993. [14] C.Mousty, O.Kaftan,V.Prevot,C.Forano,Sens.ActuatorsB:Chem.133(2008)442–448. [15] J. Das, B. Sairam Patra, N. Baliarsingh, K.M. Parida, J. Colloid Interface Sci. 316 (2007) 216–223. [16] C. Manzi-Nshuti, P. Songtipya, E. Manias, M.M. Jimenez-Gasco, J.M. Hossenlopp, C.A. Wilkie, Polymer 50 (2009) 3564–3574. [17] G.S. Thomas, P.V. Kamath, Solid State Sci. 8 (2006) 1181–1186. [18] K. Shameli, M.B. Ahmad, S.D. Jazayeri, P. Shabanzadeh, P. Sangpour, H. Jahangirian, Chem. Cent. J. 6 (1) (2012) 1–10.
7
[19] Y.L. Pak, M.B. Ahmad, K. Shameli, W.M.Z. Wan Yunus, N.A. Ibrahim, N. Zainuddin, J. 299 Nanomater. (2013) 1–9. , http://dx.doi.org/10.1155/2013/621097. 300 [20] M.B. Ahmad, J.J. Lim, K. Shameli, N.A. Ibrahim, M.Y. Tay, B.W. Chieng, Chem. Cent. 301 J. 6 (1) (2012) 1–9. 302 [21] M.B. Ahmad, J.J. Lim, K. Shameli, N.A. Ibrahim, M.Y. Tay, Molecules 16 (9) (2011) 303 7237–7248. 304 [22] Y.L. Pak, M.B. Ahmad, K. Shameli, W.M.Z. Wan Yunus, N.A. Ibrahim, N. Zainuddin, 305 Dig. J. Nanomater. Biostruct. 8 (4) (2013) 1395–1403. 306 [23] C.P. Liau, M.B. Ahmad, K. Shameli, W.M.Z. Wan Yunus, N.A. Ibrahim, N. Zainuddin, 307 Y.Y. Then, Sci. World J. (2013) 1–22 (in press). Q2308 [24] D. Basu, A. Das, K.W. Stockelhuber, U. Wagenknecht, G. Heinrich, Prog. Polym. Sci. 309 (2013) 1–33. , http://dx.doi.org/10.1016/j.progpolymsci.2013.07.011. 310 [25] Y. Kameshima, H. Yoshizaki, A. Nakajima, K. Okada, J. Colloid Interface Sci. 298 311 (2006) 624–628. 312 [26] J. Liu, G. Chen, J. Yang, Polymer 49 (2008) 3923–3927. 313 [27] Z.P. Xu, P.S. Braterman, Appl. Clay Sci. 48 (2009) 235–242. 314 [28] M.L. Hans, A.M. Lowman, Curr. Opin. Solid State Mater. Sci. 6 (2002) 319–327. 315 [29] M.J.S. Ortega, T. Stauner, B. Loretz, J.L. Ortega-Vinuesa, D. Bastos-Gonza´lez, G. 316 Wenz, U.F. Schaefer, C.M. Lehr, J. Control. Release 141 (2010) 85–92. 317 [30] J. Zhang, F. Zhang, L. Ren, D.G. Evans, X. Duan, Mater. Chem. Phys. 85 (2004) 318 207–214. 319 [31] S. Pradhan, F.R. Costa, U. Wagenknecht, D. Jehnichen, A.K. Bhowmick, G. Heinrich, 320 Eur. Polym. J. 44 (2008) 3122–3132. 321 [32] Y. Ding, Z. Gui, J. Zhu, Y. Hu, Z. Wang, Mater. Res. Bull. 43 (2008) 3212–3220. 322 [33] F.R. Costa, A. Leuteritz, U. Wagenknecht, D. Jehnichen, L. Ha¨ußler, G. Heinrich, 323 Appl. Clay Sci. 38 (2008) 153–164. 324 [34] Z. Ni, F. Xing, P. Wang, G. Cao, Appl. Clay Sci. 40 (2008) 72–80. 325 [35] S.J. Palmer, R.L. Frost, T. Nguyen, Coord. Chem. Rev. 253 (2009) 250–267. 326 [36] F. Cavani, F. Trifiro`, A. Vaccari, Catal. Today 11 (1991) 173–301. 327 [37] J. Plank, Z. Dai, P.R. Andres, Mater. Lett. 60 (2006) 3614–3617. 328
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