Science & Technology Indonesia p-ISSN: 2580-4405 e-ISSN: 2580-4391 Sci. Technol. Indonesia 1 (2016) 25-28 Article http://sciencetechindonesia.com @2016 Published under the terms of the CC BY NC SA 4.0 license 25 KEGGIN TYPE POLYOXOMETALATE H4[αSiW12O40].nH2O AS INTERCALANT FOR HYDROTALCITE Neza Rahayu Palapa1,*, Muhammad Said1 1Department of Chemistry, Faculty of Mathematic and Natural Sciences, Sriwijaya University *Corresponding Author e-mail: nezarahayu@gmail.com ABSTRACT The synthesis of hydrotalcite and polyoxometalate H4[αSiW12O40].nH2O with the ratio (2:1), (1:1), (1:2) and (1:3) has been done. The product of intercalation was characterized using FT-IR spectrophotometer, XRD, and TG-DTA. Polyoxometalate H4[αSiW12O40].nH2O intercalated layered double hydroxide was optimised to use as adsorbent Congo red dye. Characterization using FT-IR was not showing the optimal insertion process. The result using XRD characterization was showed successful of polyoxometalate H4[αSiW12O40].nH2O inserted layered double hydroxide with a ratio (1:1) which the basal spacing was expanded from 7,8 Ȧ to 9,81 Ȧ. Furthermore, the thermal analysis was performed using TG-DTA. The result show that the decomposition of polyoxometalate H4[αSiW12O40].nH2O intercalated hydrotalcite with ratio (1:1) was occured at 80oC to 400oC with a loss of OH in the layer at 150oC to 220oC, and then the decomposition of the compound polyoxometalate H4[αSiW12O40].nH2O at 350oC to 420oC. Keywords: Hydrotalcite, Layered Double Hydroxide, Polyoxometalate, Intercalation INTRODUCTION The layered material based on its existence is divided into layered material found in nature and synthesized. Hydrotalcite is a class of synthetic anionic clays whose represented by the general formula [M2+(1-x)M3+x(OH)2](An-)x/n•nH2O with the identities of M2+ and M3+ are divalent and trivalent metal cation and An is interlayer anion (Zhao et al, 2011). Hydrotalcite is modified to aim the increasing the interlayer so that it can be more effectively used. Hydrotalcite modification was done by intercalation anion macro. The macro anion used is polyoxometalate Keggin type, i.e. H4[α- SiW12O40].nH2O. Hydrotalcite intercalation by polyoxometalate used ion exchanged method. The anion macro intercalated in the hydrotalcite causes the loss of the OH- and was located on the interlayer so it can be expected to increase the distance between the layers of the hydrotalcite. In this research, synthesis and characterization of hydrotalcite, polyoxometalate H4[α-SiW12O40].nH2O and hydrotalcite intercalated by polyoxometalte H4[α- SiW12O40].nH2O to know the functional group and the success of intercalation process used Fourier characterization Transform Infra Red (FT-IR), X-Ray Diffractometer (XRD) and Thermo Gravimetric-Differential Thermal Analysis (TG- DTA). EXPERIMENTAL SECTION Materials The chemicals used are qualified materials such as sodium metasilica, sodium tungstate, hydrochoric acid, pottasium hydroxide, pottasium chloride, diethyl ether, sodium hydroxide, sodium carbonate, magnesium nitrate and aquadest. Article History Submitted: 29 March 2016 Accepted: 24 April 2016 DOI: 10.26554/sti.2016.1.1.25-28 Methods Synthesis Hydrotalcite Hydrotalcite was synthesized in a solution with a concentration of 50 mL of Mg(NO3)2 1M and 20 mL of Al(NO3)3 1M wa s added by rapidly stirring into 250 mL of distilled water at pH value 10 of 5 mL of NaOH 2M at teazmperature 40 ̊C. The reaction was maintained at a pH value of 10 then simultaneously added 20 mL of Na2CO3 2M and 10 mL of NaOH 2M. The product obtained is white suspension and is still stirred for 3 hours at 40 ̊C and left at 70 ̊C for 40 hours. The obtained product is filtered, washed with aqua dest and dried at room temperature. The structure, term stability and product texture of hydrotalcite were characterized by FT-IR Spectrophotometer, XRD, and TG-DTA. Polyoxometalat H4[α-SiW12O40]•nH2O Polyoxometalat H4[α-SiW12O40]•nH2O was synthesized by dissolving methanolic sodium as much 2,75 grams into 25 mL of aqua dest was used as solution A. 45,5 grams of sodium tungstate dissolve into 75 mL of boiled aqua dest and this solution becomes B solution. 41,25 mL of HCl 4M was added slowly for 5 minutes with strong stirring to dissolve the precipitate of tungstic acid. Then, solution A was added rapidly into solution B with an addition of 12,5 mL of HCl 4M. The solution was kept for an hour at 100 ̊C at pH value of 5 to 6. 12.5 mL of sodium tungstate and 20 mL of HCl 4M are added to the solution rapidly. This solution is filtrated after cooling at room temperature. The solution is used to obtain a salt or α- [SiW12O40]4- acid. Potassium salt was obtained by adjusting the solution to a pH value of 2 using a KCl of 12.5 grams rapidly to obtain a white sediment from potassium salt to form K4[α- SiW12O40]. To obtain H4[α-SiW13O40] polyoxometalate acid by extraction of a white sediment from potassium salt to form K4[α-SiW12O40] using 20 mL diethyl ether and 30 mL of diethyl ether and concentrated hydrochloric acid (1: 1) which had mailto:nezarahayu@gmail.com Palapa et al. / Science and Technology Indonesia 1(1) 2016:25-28 @2016 Published under the terms of the CC BY NC SA 4.0 license 26 previously been cooled to Temperature 0 ̊C. The bottom layer is taken and concentrated to obtain white crystals which are recrystallized using quads so as to obtain polyoxometalate acid H4[α-SiW12O40]•nH2O. The characteristic of H4[α-SiW13O40] was performed using FT-IR spectroscopy and XR analysis. Preparation of Hydrotalcite intercalated by Polyoxometalate H4[αSiW12O40]•nH2O Intercalated hydrotalcite by polyoxometalate H4[α- SiW13O40] used ion exchanged method with weight variation ratio of each hydrotalcite : polyoxometalate (2:1), (1:1), (1:2) and (1:3) is by preparing a solution of 1 grams polyoxometalate H4[α-SiW13O40] 1 M distilled with 50 mL of aqua dest and 1 grams hydrotalcite was added to 25 mL of NaOH 1M.. Solution A and solution B were mixed rapidly under conditions of N2 gas sterilized for 24 hours. The suspension is cooled and the product is washed with water and dried at room temperature. The structural analysis and the thermal stability of intercalated product are identifed using XRD, FT-IR, and TG-DTA. RESULTS AND DISCUSSION Characterization of Hydrotalcite and Polyoxometalate H4[α-SiW12O40]•nH2O and the result using FT-IR Spectrophotometer The FT-IR spectrum of hydrotalcite is presented in Figure 1a. It is seen that the widespread vibration peak between the wave number 3800-3300 cm-1 is the vibration of the OH group within the hydrotalcite structure. The presence of a detected peak at the 1635 cm-1 is a bending OH vibration. In the wave number 1381 cm-1, there is a vibration which is an asymmetrical stretch of nitrate and a nitrate bend at wave number 671 cm-1. Vibration Al-O and Mg-O are at wave numbers 601 cm-1 dan 408 cm-1 (Handayani, et al.2014) Polyoxometalate H4[α-SiW12O40]•nH2O has the vibration at 3448 cm-1. In Figure 1b, identifies the presence of H2O contained in the polyoxometalate H4[αSiW12O4t0].nH2O. characteristic of polyoxometalate H4[αSiW12O40].nH2O has shown in the wave number 925 cm-1 for Si-O vibration and wave number 794 cm-1 for W-O-W vibration. Hydrotalcite intercalated by polyoxometalate H4[α- SiW12O40].nH2O ratio 2:1; 1:1; 1:2; and 1:3 is presented in Fig. 1c, d, e, and f. Hydrotalcite intercalated by polyoxometalate H4[α-SiW12O40].nH2O ratio 2:1; 1:1; and 1:2 did not show the characteristic of polyoxometalate H4[α-SiW12O40].nH2O wherein 3 peaks at wave number 980-770 cm-1, but only the widespread nitrate bending of wavenumber 820-550 cm-1 was shown. As for hydrotalcite intercalated by polyoxometalate ratio 1:3, the FT-IR spectra shown the vibration at wavenumber 833 cm-1 indicated the presence of polyoxometalate H4[α- SiW12O40].nH2O and then more identified using X-ray Diffraction. Characterization of Hydrotalcite and Polyoxometalate H4[αSiW12O40]•nH2O and The Intercalation Result Using X-ray Difraction Polyoxometalate H4[α-SiW12O40].nH2O was characterized using XRD. The pattern is shown in Fig. 2. Polyoxometalate H4[α-SiW12O40]•nH2O has a diffraction at 2θ is 8, 9, 18 and 27o. Distractions for polyoxometalate is generally present at 6-10°, 15-20°, 22-25° and 35-40° (Yang et al, 2011). Hydrotalcite and Hydrotalcite intercalated by polyoxometalate are shown in Fig 3. Hydrotalcite pattern of XRD has shown the layered structure is located at the diffraction at 2θ is 11o intensity 106 and the basal spacing is 7,4 Ȧ and the peak in the diffraction pattern 2θ of 60o indicates that the presence of anions on the interlayer (Dolidovich and Palkovits, 2015). Figure 1. FT-IR Spectra a) Hydrotalcite, b) polyoxometalate H4[αSiW12O40]•nH2O, c) hydrotalcite intercalated by polyoxometalate H4[αSiW12O40]•nH2O 2:1, d) 1:1, e) 1:2 dan f) 1:3. Figure 2. Pattern of polyoxometalat H4[αSiW12O40]•nH2O Hydrotalcite intercalated by polyoxometalate H4[αSiW12O40]•nH2O with ratio 2:1; 1:1; 1:2; and 1:3 have been characterized and the result is shown in Fig 3. The diffraction at 2θ is 11,2o intensity 265 and basal spacing 7,87 Ȧ. The presence of a new diffraction peak occurring in the region of 22.9o denotes the typical peak of polyoxometalate H4[α- SiW12O40].nH2O intensity 116 and basal spacing 3,8 Ȧ is shown Fig 3a. In addition, Fig 3b has explained the highest diffraction at 2θ is 10,8̊, intensity is 342 and basal spacing is 9,81 Ȧ, and diffraction at 22,5̊ which is the diffraction peak of a polyoxometalate intensity 141 and basal spacing 3,6 Ȧ. Fig 3c and 3d were showing the same diffraction as hydrotalcite. This Palapa et al. / Science and Technology Indonesia 1(1) 2016:25-28 @2016 Published under the terms of the CC BY NC SA 4.0 license 27 condition shows that hydrotalcite intercalated by polyoxometalate H4[αSiW12O40].nH2O ratio 1:1 more better than others because this ratio has the better diffraction and the highest basal spacing which shown polyoxometalate H4[α- SiW12O40].nH2O has intercalated into hydrotalcite and caused increased the basal spacing. Figure 3. XRD Pattern a) Hydrotalcite, , b) Hydrotalcite intercalated by polyoxometalate H4[αSiW12O40]•nH2O 2:1, c) 1:1, d) 1:2 dan e) 1:3. Characterization of Hydrotalcite and Hydrotalcite intercalated by Polyoxometalate H4[αSiW12O40]•nH2O Usi ng TG-DTA Hydrotalcite and Hydrotalcite intercalated by Polyoxometalate H4[α-SiW12O40]•nH2O has characterized using TG-DTA analysis by program temperature starting from 25oC to 950oC using N2 gas yielding thermogram pattern as presented in Figure 4 and Figure 5 . Figure 4. Thermogram of Hydrotalcite Figure 4 shows that the hydrotalcite decomposes with the loss of water molecules with an endothermic peak at temperatures of 50-100°C with a mass loss of 23%. (Xie, 2006). At temperature 200-320oC has showing decomposes OH- of hydrotalcite at interlayer was marked widening endothermic peak along loss the carbon dioxide at temperature 270-330 oC a total lost mass is 15,21%. The results of this TG-DTA measurements show similarities with the research conducted by Frost et al (2005) which shows the loss of OH groups in the interlayer layer along with the loss of CO2 at temperature 300- 400oC. At temperature 650-770oC, there is a decomposition of hydrotalcite in the presence of an endothermic peak marked by loss of carbonate anion attached to chemically bonded Mg2+ and Al3+ is 22,89 % (Lin et al, 2001). Figure 5 shows the decomposition at temperature 150- 220oC with the loss OH in interlayer (Zhang et al, 2012). According to Khozhevnikov (2002), thermogram pattern has shown decomposition at 350-420oC is decomposition of polyoxometalate H4[α-SiW12O40]•nH2O with the loss hydrogen bonding of polyoxometalate H4[α-SiW12O40]•nH2O of ion hydroxide. Figure 5. Thermogram Hydrotalcite intercalated by polyoxometalate H4[αSiW12O40]•nH2O ratio (1:1). CONCLUSION Hydrotalcite has been successfully intercalated by polyoxometalate H4[αSiW12O40]•nH2O ratio of mass hydrotalcite: polyoxometalate H4[αSiW12O40]•nH2O which optimum is ratio 1:1. Hydrotalcite intercalated by Polyoxometalate H4[αSiW12O40]•nH2O, with mass ratio 1:1 has characterization using FT-IR spectrophotometer, XRD, and TG-DTA. The result of FT-IR spectrophotometer have not shown the optimal intercalated process, characterization of XRD was shown that the diffraction at 2θ is 10,8̊ with intensity 342 dan basal spacing is 9,81 Ȧ, and diffraction at 22,5̊ is characterized of polyoxometalate H4[αSiW12O40]•nH2O. the thermal analysis was carried out using TG-DTA into hydrotalcite intercalated by polyoxometalate H4[αSiW12O40]•nH2O was decomposition at 80oC until 400oC with loss OH in interlayer at 150-220oC while for decomposition of polyoxometalate H4[αSiW12O40]•nH2O at temperature 350-420oC. 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