Science & Technology Indonesia p-ISSN: 2580-4405 e-ISSN: 2580-4391 Sci. Technol. Indonesia 1 (2016) 16-19 Article http://sciencetechindonesia.com @2016 Published under the terms of the CC BY NC SA 4.0 license 16 Mg/Al DOUBLE LAYER HYDROXIDES: INTERCALATION WITH H3[α-PW12O40]•nH2O Yulizah Hanifah1,* and Neza Rahayu Palapa1 1Department of Chemistry, Faculty of Mathematic and Natural Sciences, Sriwijaya University *Corresponding Author e-mail : yulizahanifah@gmail.com ABSTRACT It has been done the intercalation of polyoxometalate H3[α-PW12O40]•nH2O on Mg-Al double layer hydroxide by comparison weight ratio of double layer hydroxides : polyoxometalate H3[α-PW12O40]•nH2O, i.e: 1:1, 1:2, 1:3 and 1: 4. The product of intercalated double layer hydroxide was characterized using FT-IR spectrophotometer, XRD, and TG-DTA analysis. The spectrophotometer results of FT-IR shown the process of intercalation was not optimum for every weight ratio. Characterization using XRD showed the process of intercalation was optimum at a ratio 2:1 that indicated at the area of 11,12o, 22,85o and 34,5o as double layer hydroxide and at the area of 60-63o showed the double layer hydroxide has intercalated with polyoxometalate. The characterization results using TG- DTA analysis at the comparison 2:1 showed loss of OH in the layer at 170 to 220°C and for the decomposition of polyoxometalate H3[α-PW12O40]•nH2O at 300 to 400°C. Keywords: Double Layer Hydroxide, Intercalation, Polyoxometalate H3[α-PW12O40]·nH2O INTRODUCTION Layered materials or clay of inorganic minerals are found in nature and can also be synthesized in the laboratory (Abderrazek et al, 2016). Layered material is used as a catalyst, adsorbent, sensor, membrane or ion exchange. As adsorbent, a layered material used for aditive adsorption on vegetable oil (Franchi et al, 1991) as well as its application for the control of contamination of metal ions or organic compounds in the environment. The advantages of this double layer hydroxide have a great anion exchange properties and can be exchanged for various other anions (Beaudot et al, 2004). The general formula for double layer hydroxide is [M2+(1-x)M3+x(OH)2](An-)x/n•nH2O which in that positive charges are balanced by the interlayer anions such as Cl-, NO3- and CO3 (Guo et al, 2014). However, The use of these layered materials still has small surface area constraints and narrow layer spacing due to the small exchange ions which are generally alkali and alkaline earth metal ions (Goodarzi et al, 2016). Double layer hydroxide still needs to be modified to increase its surface area and majority modifications made to this research are through intercalation of layered materials with atoms, molecules and complex compounds using ion exchange methods. The purpose of this intercalation process is expected to produce double layer hydroxide intercalated macro anion that automatically increasing interlayer so it can be used as adsorbent or catalyst. The macro anion is used Polyoxometalate Keggin type H3[α-PW12O40]·nH2O. The intercalated macro anion of double layer hydroxide causes the loss of the OH- anion that located on the layer so it is expected to increase the distance between layers of the double layer hydroxide. Article History Submitted: 2 June 2016 Accepted: 5 August 2016 DOI: 10.26554/sti.2016.1.1.16-19 In this research, synthesis and characterization of double layer hydroxide, polyoxometalate H3[α-PW12O40]·nH2O and double layer hydroxide intercalated polyoxometalate H3[α- PW12O40]·nH2O has been done. Characterization has been conducted using Fourier Transform Infra Red (FT-IR), X-Ray Diffractometer (XRD) and Thermo Gravimetric-Differential Thermal Analysis (TG-DTA). EXPERIMENTAL SECTION Material and Methods Double layer hydroxide intercalated with H3[α- PW12O40]·nH2O was performed by ion exchanged method. Characterization of the synthesized compounds was performed by different techniques such as FTIR, X-Ray Diffractometer (XRD). XRD was performed using Shimadzu Lab X-type 6000 to determine the surface area before and after intercalated. The TG-DTA analysis of double layer hydroxide intercalated Polyoxometalate H3[α-PW12O40]·nH2O was evaluated using Shimadzu TG / DTA 60A analyzer from 20°C to 800 °C. Preparation of Mg-Al LDH and H3[α-PW12O40]·nH2O composite Preparation of Mg-Al LDH Mg-Al LDH was synthesized by mixing 64.01 g of Mg(NO3)2.6H2O (2 mol) and 46.64 g of Al(NO3)3.9H2O (1 mol) were dissolved in 150 mL of aquadest (solution A). 10.00 g of NaOH and 26.62 g of NaCO3 was poured into 150 mL aquadest (solution B). Solution A is added to solution B and stirred gradually with the addition of aquadest of 100 mL and a pH adjusted from 9 to 10 to form sediment. The sediment is dried into oven at 80 °C and ready to be characterized using FT- IR spectroscopy and XRD analysis. Preparation of Polyoxometalate H3[α-PW12O40]·nH2O composites 125 g of sodium tungstate and 20 g of sodium phosphate were mixed with 187.5 ml of boiling water in 500 mL of a glass Hanifah et al. / Science and Technology Indonesia 1(1) 2016:16-19 @2016 Published under the terms of the CC BY NC SA 4.0 license 17 beaker. 100 ml of hydrochloric acid is added dropwise to the mixture and stirred using a magnetic stirrer. The stirring process is continuous until all the solid dissolve. The phosphotungstate acid will begin to separate when half of the hydrochloric acid is added then the resulting solution becomes clear and cooled. A 75 mL of diethyl ether cold solution was added and then extracted. After extraction process obtained three layers, the solution separated and taken from the bottom layer. The lowest layer was evaporate using a rotary evaporator to obtain white solid that is H3[α-PW12O40]·nH2O. Characterization of H3[α- PW12O40]·nH2O was performed using FT-IR spectrophotometer and XRD analysis. Intercalation of LDH-POM Intercalation process of double layer hydroxides by polyoxometalate H3[α-PW12O40]·nH2O by ion exchange method was carried out by preparing 1 g of H3[α-PW12O40]·nH2O (solution A) mixed with 50 mL of distilled water, and 2 g of double layer hydroxide was added with 25 mL NaOH 1 M (solution B). Solution A and solution B are then mixed rapidly under conditions given N2 gas for 24 hours. Then the suspension is cooled and the product is washed with water and dried at room temperature. Structural analysis, the thermal stability of the inserted product is carried out using XRD, FT- IR and TG-DTA. RESULTS AND DISCUSSION Characterization of LDH-POM Mg-Al LDH and LDH-POM using comparison 1:1, 1:2, 1:3 and 2:1. The characterization of the FT-IR spectra aims to identify the functional groups formed as shown in Figure1. Figure 1. FT-IR spectra of (A) double layer hydroxide (B) Polyoxometalate H3[α-PW12O40]·nH2O (C) Intercalation LDH- POM with a rasio 1: 1 (D) 1: 2 (E) 1: 3 (F) 2: 1. The FT-IR spectrum of LDH is presented in Figure 1. At 671 and 1381 cm-1 which are indicated nitrate bend and the symmetric stretch of nitrate (Handayani, 2013). On the other hand, the characteristic peak of LDH at 601, 408 cm-1 which are Al-O and Mg-O vibration. Figure 1B shows the peaks of the functional group of PolyoxometalateH3[α-PW12O40]·nH2O. The characteristic of Polyoxometalate is shown at 802, 894, 987 and 1080 cm-1 which are related to the W-Oc-W, W-Ob-W, W=O, and P-O. Figure 1C in comparison LDH-POM (1:1) shows the presence of a vibrational peak at 3479.5 cm-1 which are related to O-H group vibration. The absorption band at 1635.6 cm-1 is indicated buckling of the adsorbed O-H group on interlayer and absorbing bands at 1381 cm-1 showing symmetrical nitrate synthesis yield of double layer hydroxide. The three vertices of this vibration are also shown in the FT-IR spectrum of Figure 1D (1:2), 1E (1:3) and 1F (2:1). These three peaks indicate the presence of double layer hydroxide material. The differences presented based on the FT-IR spectrum in Figure 1 are shown by the presence of Polyoxometalate. Figure 1C show a vibration peak for a polyoxometalate at 663 cm-1 which is a vibration of W-Oc-W. Figure 1D shows the peak vibration of polyoxometalate at 887-810, 987 and 1080 cm-1 which are related to the W-Oc-W, W-O, and P-O vibration. In Figure 1E at 1018 and 786 cm-1 are related W-Oc-W and P-O vibration. Whereas in Figure 1 F shows the existence of polyoxometalate at 671 cm-1 is W-Oc-W vibration. Characterization of LDH, Polyoxometalate H3[α- PW12O40]·nH2O and Intercalation Result Using X-Ray Difraction Polyoxometalate H3[α-PW12O40]·nH2O characterization using XRD. The diffraction is shown in Figure 2. Figure 2. X-ray diffraction of polyoxometalate H3[α- PW12O40]·nH2O Figure 2 shows the X-ray diffraction patterns of H3[α- PW12O40]·nH2O with the principal regions of 2θ ie 6-10o, 15- 20o, 22-25o and 35-45o wherein those diffractions are characteristic for crystalline Polyoxometalate H3[α- PW12O40]·nH2O (Zhang et al, 2012). The results of the measurement analysis are known to have the largest peaks appear in regions 7o and 37–45o. The presence of diffraction patterns that appear in the 2θ region below 10o denotes the typical peak of the polyoxometalate MO6 where M is tungsten and has high crystallinity. Polyoxometalate H3[α- PW12O40]·nH2O are subsequently intercalated into a double layer hydroxide material which aims to increase the distance 2θ (Degree) Wavenumber (cm-1) T (% ) Hanifah et al. / Science and Technology Indonesia 1(1) 2016:16-19 @2016 Published under the terms of the CC BY NC SA 4.0 license 18 between the double layer hydroxide layers. The double layer hydroxide material and the intercalated double layer hydroxide are presented in Figure 3. From the Figure3A, Double layer hydroxide diffraction was showing the highest peak at 27o-29o which is demonstrated double layer hydroxide material. Figure 3B shows the interfraction pattern of double layer hydroxide material intercalated polyoxometalate with the ratio (1: 1) there is the highest diffraction peak that is in the area at 10,8o, 22,4o and 8,9o. Figure 3B shows diffraction peak at 10.8°, 22.4o and 34.1° are having relatively high crystallinity (Kloprogge et al 1999). According, to Wiyantoko (2015), these three diffraction shows the properties of double-layer hydroxide materials, which have layered structures with intensity are 340, 156 and 101. The regions appearing at 60-63o indicate the presence of anions in the interlayer of the layered material. Based on this data can be expressed comparison compared to the ratio in (1: 1), (1: 3) and (2: 1). Figure 3. Diffractogram XRD (A) Double layer hydroxide (B) Intercalation of Double Layered Hydroxide with Polyoxometalate with a rasio of 1: 1 (C) 1: 2 (D) 1: 3 (E) 2: 1. Figure 3C shows the different angles of the diffraction form showing the existence of double layer hydroxide material at 2θ = 10.9o. 22.88o and 34.4o and indicating the diffraction of the success of the anions, which is presented in a double layer hydroxide material at 60.4o and 61.7o with a relatively smaller intensity than the diffraction Fig (1: 1) and (2: 1). Figure 3 D (1:1) is successfully synthesized wherein the polyoxometalate enters the interlayer of the double layer hydroxide material. Figure 3E also shows the existence of double layer hydroxide material at 2θ = 11.12o, 22.85o and 34.5o which have greater intensity are 518, 192 and 133 than on comparison (1: 1), (1: 2) and (1: 3). The diffraction shows the success of intercalation process of double layer hydroxide material with polyoxometalate at 2θ=60,4o and 61,7o which has greater intensity than on (1: 1), (1: 2) and (1: 3) are 71 and 72. Characterization of LDH and LDH Intercalated Polyoxometalate H3[α-PW12O40]·nH2O Using TG-DTA Double layer hydroxide obtain was then characterized using TG-DTA analysis. The purpose of Thermogravimetric Analyzer (TGA) analysis was used to record changes in sample weight as a function of temperature and Differential Thermal Analyzer (DTA) to detect changes in the heat content. The TG-DTA analysis of the double layer hydroxide has a thermogram pattern as shown in Figure 4. Figure 4 shows the double layer hydroxide decomposed with the loss of water molecules at 77-102°C with weight loss about 23% (Xie, 2006). From the thermogram could be seen a sharp peak DTA at a temperature of 77-102°C. Figure 4. Termogram of Double Layer Hydroxide Material At 300-320°C, which is the decomposition of the OH group of the interlayer material of the double layer hydroxide material with a loss of weight is 15.22% indicated on the red line ie the weight loss. The endothermic peak at 308 °C indicates loss of carbonate (Li, et al. 2013). According to Yu (2009), dehydroxylation process and loss of Mg/Al-CO3- ions at the endothermic peak are seen at temperatures around 220oC. The endothermic peak at 650-750oC indicates a double layer hydroxide material decomposition in the presence of an endothermic peak marked by loss of carbonate ions attached to Mg2+ dan Al3+ with a weight loss about 22.89% (Lin et al, 2001). The intercalation of double layer hydroxide with polyoxometalate H3[α-PW12O40]·nH2O by weight ratio (2: 1) has a thermogram pattern as in Figure 5. Figure 5. Thermogram Intercalation Result of Double Hydroxy with Polyoxometalate H3[α-PW12O40]·nH2O Hanifah et al. / Science and Technology Indonesia 1(1) 2016:16-19 @2016 Published under the terms of the CC BY NC SA 4.0 license 19 Figure 5 shows the presence of three endothermic peaks. The first endothermic peak at a temperature of 20-90 oC is due to the loss of water molecules. At the second endothermic peak at temperatures of 170-220 oC is demonstrated the decomposition marked by the loss of the OH group present in the interlayer (Zhang et al, 2012). The third endothermic peak is at a temperature of 300-400 °C which is a decomposition of a polyoxometalate H3[α- PW12O40]·nH2O with loss of hydrogen bonds between H3[α- PW12O40]·nH2O with hydrogen ions (Khozhevnikov, 2012). 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