Science and Technology Indonesia e-ISSN:2580-4391 p-ISSN:2580-4405 Vol. No. October 2019 Research Paper Intercalation Zn/Cr Layered Double Hydroxides with K3 . u-PW12 O40 ]nH2 O and K4 . u-SiW12 O40 ]nH2 O as Adsorbent of Rhodamine-B Jeri Rahmadan1 . Tarmizi Taher2 . Neza Rahayu Palapa1 * Aldes Lesbani1 . Risfidian Mohadi2 1 Department of Chemistry. Faculty of Mathematic and Natural Sciences. Universitas Sriwijaya. Jl. Palembang Prabumulih Km. 32 Ogan Ilir 30662. Indonesia 2 Environmental Science Study. Graduate Program. Universitas Sriwijaya. Jl. Padang Selasa Bukit Besar Palembang 30139. Indonesia *Corresponding author: nezarahayu@gmail. Abstract Synthesis of Zn-Cr layered double hydroxide intercalated with polyoxometalate K3 . u-PW12 O40 ]nH2 O and K4 . uSiW12 O40 ]nH2 O was conducted successfully. The characterization of layered double hydroxide intercalated was performed using XRD and FT-IR analyses. After that layered double hydroxide intercalated used as an adsorbent of rhodamine B (RhB) dye. The results show Rhodamine-B (RhB) more effective adsorbed using the Zn-Cr adsorbent K3 . u-PW12 O40 ]nH2 O than using an intercalated adsorbent K4 . u-SiW12 O40 ]nH2 O because the distance between the layers is smaller. Study of kinetics showed that the adsorption process is more fits with PSO than PFO based on coefficients correlation. The adsorption process described by Langmuir isotherm models for all adsorbent. The value of enthalpy and entropy shows that the adsorption process was endothermic and negative free energy value was indicated that the process was spontaneous. Keywords layered double hydroxides, intercalation. Keggin ion, rhodamine-B Received: 28 September 2019. Accepted: 25 October 2019 https://doi. org/10. 26554/sti. INTRODUCTION The rapid economic growth has caused environmental dis-order with huge pollution problems. The demand for water has increased tremendously in agricultural, industrial and domestic This has resulted in the generation of large amounts of wastewater containing a high number of contaminants. Many industries, such as textiles, paper, and plastic, use dyestuffs in order to color their products (Aljeboree et al. , 2. Dyes that are often used in the textile industry rhodamine B (RhB). Dyes are resistant to direct biodegradation and photolysis and many N-containing dyes can experience degradation of undergoing natural reductive anaerobic degradation to yield potentially carcinogenic aromatic amines (Laipan et al. , 2. If rhodamine B (RhB) dye accumulates in the human body it can cause some health problems in humans (Han et al. , 2. Many methods have been developed to remove dyes from wastewater including membrane filtration, precipitation, coagulation, flocculation, chemical oxidation, solvent extraction, biodegradation and adsorption (Taher et al. , 2. The adsorption method is an efficient technique to deal with the problems of domestic and industrial wastewater contamination because it can eliminate odors and reduce the level of the dye from the solution perfectly without turning it into a more dangerous com- pound (Gaini et al. , 2009. Palapa et al. , 2019. One process for removing dyes through the adsorption process uses porous and layered materials, for example, layered double hydroxide. Layered double hydroxide compounds are compounds which in structure occur partial substitution of trivalent metal with divalent metal. This substitution creates a positive charge in the hydroxide layers (Palapa et al. , 2019a. Tichit et al. , 2. The advantages of this double layer hydroxide have great anion exchange properties and can be exchanged for various other anions (Antonyraj et al. , 2010. Guo et al. , 2. The general formula for double layer hydroxide is [M2 . Oe. M3 x(OH)2 ](AnOe )x/n. nH2 O which in that positive charges are balanced by the interlayer anions such as ClAe. NO3Oe and CO3 (Antonyraj et al. , 2010. Palapa et al. , 2. 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 (Han et al. , 2. Layered double hydroxide still needs to be modified to increase itAos 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. In this research, synthesis, and characterization of layered double hydroxide, polyoxometalate K3 . u-PW12 O40 ]nH2 O and K4 . u-SiW12 O40 ]nH2 O and layered double hydroxide interca- Ramadhan et. lated polyoxometalate K3 . u-PW12 O40 ]nH2 O and K4 . u-SiW12 O40 ] nH2 O has been done. Characterization has been conducted using XRD and FT-IR. Zn-Cr layered double hydroxide intercalated polyoxometalate compound K3 . u-PW12 O40 ]nH2 O and K4 . u-SiW12 O40 ] nH2 O can be used as rhodamine B (RhB) dye The factors that influence the adsorption process to be studied in this study are the effects, adsorption time, concentration and temperature. The investigation of kinetic, thermodynamic and isotherm adsorption was discussed. EXPERIMENTAL SECTION 1 Chemicals and Instrumentation Layered double hydroxide intercalated with K3 . u-PW12 O40 ] nH2 O and K4 . u-SiW12 O40 ]nH2 O was performed by ion-exchange Characterization of the synthesized compounds was performed by different techniques such as FTIR and X-Ray Diffractometer (XRD) FTIR spectrophotometer was conducted using Shimadzu FTIR Prestige21 using KBr disk and scanning was performed at wavenumber 400-4000 cmOe1 . XRD was conducted using Rigaku Miniflex-600 and scanned at 0. 1 deg minOe1 . Analysis of rhodamine B (RhB) was used UV-Vis spectrophotometer double beam Biobase BK-UV 1800. 2 Preparation of Zn-Cr LDH Zn-Cr layered double hydroxides were synthesized by coprecipitation method at constant pH 10. Zn(NO. 2 A H2O . mL, 0. M) and Cr(NO. 3 A H2O . mL, 0. 25 M) with the molar ratio 2:1 were stirring for an hour. Then, 100 mL of sodium carbonate 5 M at 60 AC was added slowly. The solution was added with 25 mL of sodium hydroxides 3 M and the mixtures were slowly stirring at 60 AC for 24 hours. The solution kept at pH 10 to form gray solid bulky material. After that, the gray material was washed with water and kept overnight at 60 AC to obtain Zn-Cr layered double hydroxides. Characterization of Zn-Cr layered double hydroxides was performed using XRD powder analysis and IR spectroscopy (Oktriyanti et al. , 2. 3 Preparation of Polyoxometalate K3 . u-PW12 O40 ] nH2 O 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 beaker. 100 ml of hydrochloric acid is added dropwise to the mixture and stirred using a magnetic stirrer. The stirring process is continued until all the solids 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 the 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 a white solid that is K3 . uPW12 O40 . Characterization of K3 . u-PW12 O40 was performed using XRD and FT-IR spectrophotometer analysis. 4 Preparation of Polyoxometalate K4 . u-SiW12 O40 ]nH2 O 11 g of sodium metasilicate in 100 mL of water which is used as a 182 g of sodium tungstate is dissolved in 300 mL of hot A 2019 The Authors. Science and Technology Indonesia, 4 . 109-114 water and this solution is made as a solution B. 165 mL HCl 4 M was added dropwise for 5 minutes into solution B with strong stirring to dissolve the precipitate from tungstic acid. Then, solution A is added quickly to solution B followed by adding 50 mL of 4M HCl. The solution was maintained for 1 hour at 100 AC at a pH value of 5 to 6. 50 mL sodium tungstate concentrations of 1 M and 80 mL of 4M HCl were added to the solution quickly. This solution is filtered after being cooled at room temperature. The solution is used to obtain salt or yu-SiW12 O40 . The potassium salt is obtained by adjusting the solution at a pH value of 5 using 50 g of KCl quickly to obtain white deposits from potassium salts to form K4 . u-SiW12 O40 ]nH2 O. Characterization was performed using XRD and FT-IR spectrophotometer analysis. 5 Intercalation of LDH-POM Intercalation process of layered double hydroxide by polyoxometalate K3 . u-PW12 O40 ] nH2 O or K4 . u-SiW12 O40 ]nH2 O by ion exchange method was carried out by preparing 1 g of Polyoxometalate . olution A) mixed with 50 mL of distilled water, and 2 g of double layer hydroxide was added with 25 mL NaOH 1 M . olution 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 and FT-IR spectrophotometer analysis. 6 Adsorption Experiment Preparing rhodamine B (RhB) solution by 1 g of solid rhodamine B(RhB) powder with 1000 mL of water to obtain 1000 mg/L as dye stock solution. The standard solution prepared by diluting dye stock solution. To obtain a standard curve of the dyes solution, dyes were measured of each standard solution using spectrophotometer UV-Vis at the maximum wavelength, respectively. The adsorption of dyes was conducted in a batch system. An amount of adsorbent was added into 50 mL of dyes solution then mixture using horizontal shaker at 250 rpm at a constant temperature for any predeterminate time. The solution was filtered and measuring using UV-Vis spectrophotometer. In order to study the effect of time adsorption, the experiment set up as follow. 05 g of adsorbent was added to 50 mL of dyes solution then shake at a varying time with temperature 303 AK and the concentration of dyes solution was 45 mg/L. The thermodynamic parameters investigated based on two kinetic parameter models, pseudo-first-order and pseudosecond-order. The thermodynamics studied by varying initial concentration, the experiment set up as follow. 05 g of adsorbent added to 50 mL of varying concentration dyes solution. Then shake in varying temperature 303-343 AK. RESULTS AND DISCUSSION Fig. 1 shows the XRD patterns of the products. The pattern in Fig. 1a clearly indicates the layer structure of the Zn-Cr-K4 . uSiW12 O40 ] nH2 O LDHs with characteristic peaks . ssigned a. 35A, 34. 16A and 60. 02A with each basal spacing at 9. 45 yI, 4. Page 110 of 114 Science and Technology Indonesia, 4 . 109-114 Ramadhan et. yI, 2. 64 yI and 1. 53 yI was observed with low intensity, and Fig. 1b shows the interfraction pattern of layered double hydroxide material intercalated polyoxometalate K3 yu-PW12 O40 there is the highest diffraction peak that is in the area at 9. 36A, 23. 34A, 27. 98A and 60,17A with each basal spacing of 9. 38 yI, 3. 81 yI, 3. yI, 2. 71 yI and 1,54 yI. Estimated the best formation of ZnAeCrAe K4 yu-SiW12 O40 and Zn-Cr-K3 yu-PW12 O40 LDHs (Lafi et al. , 2. Table 1. Kinetics Parameters Adsorption of Dye Rhodamine B (RhB) by LDHs Kinetics Models Parameters PFO Qe Exp . Qe Calc . inOe1 ) Qe Exp . Qe Calc . inOe1 ) PSO Adsorbent Zn-Cr-PW Zn-Cr-SiW 0,031 0,913 Figure 1. XRD pattern of layered double hydroxides Figure 3. Time adsorption of dye rhodamine B (RhB) by LDHs Figure 2. FT-IR spectra of layered double hydroxides Fig. 2 shows the FT-IR spectra of the synthesized layered double hydroxide material intercalated polyoxometalate K3 . uPW12 O40 ] nH2 O and K4 . u-SiW12 O40 ]nH2 O . Fig. 2a-2b The intensity at wavenumber 3448 cmOe1 is assigned to the OH stretching vibration . Wavenumber at 1635 cmOe1 is assigned as OH bending in the interlayer water molecule. Wavenumber 9 cmOe1 and 848. 68 cmOe1 is assigned as Zn-O and Cr-O Wavenumber 840. 96 cmOe1 shows the presence of vibrations from Si-O. Wavenumber 1064,71 cmOe1 is assigned as P-O vibration. Wavenumber 1026,13 cmOe1 is assigned as W=O vibration. Wavenumber 516. 92 cmOe1 is assigned as W-Oc-W group vibration (Palapa et al. , 2019b. Oktriyanti et al. , 2. Wavenumber of 1381. 03 cmOe1 the width of the peak means that some nitrate anions have been replaced by anions . uSiW12O. 4Oe and . uPW12O. 4Oe . A 2019 The Authors. 1 Effect of Contact Time and Kinetic Parameters Effect of adsorption time of dye rhodamine B (RhB) by Layered double hydroxide intercalated shown in Fig. The adsorption of rhodamine B (RhB) on Zn-Cr-K3 . u-PW12 O40 ] nH2 O LDHs showed the adsorption faster than Zn-Cr-K4 . u-SiW12 O40 ]nH2 O. The maximum of adsorption time on rhodamine B (RhB) by Zn-Cr-K3 . u-PW12 O40 ] LDHs at 100 min with maximum uptake 26,099 mg/g whereas the maximum adsorption on rhodamine B (RhB) by Zn-Cr-K4 . u-SiW12 O40 ]nH2 O at 100 min with maximum uptake 24,501 mg/g. According to this research. use Zn-Cr-K3 . u-PW12 O40 ] LDHs basal spacing greater, because it is influenced by the distance between layers. the greater the distance between layers, the more adsorbates are adsorbed by the adsorbent because of the more active sites on the adsorbent bind to rhodamine B (RhB) dyes. LDHs is better to remove the anionic dyes (Aguiar et al. , 2013. Palapa et al. , 2. In order to identify the kinetics parameter adsorption process, two kinetic models i. Pseudo-first-order and pseudo-secondorder are applied. The kinetic parameters are calculated using the pseudo-first-order and pseudo-second-order equations as ycoycuyci. cEyce Oe ycEy. = ycoycuyciycEyceyco1 /. yc/ycEyc = . /yco2 ycEyce 2 ) . /ycEyc. Page 111 of 114 Science and Technology Indonesia, 4 . 109-114 Ramadhan et. Figure 4. Adsorption isotherm of rhodamine B (RhB) by Zn-Cr- PW LDHs . Zn-Cr- SiW LDHs . at several temperatures Figure 5. RL versus Ce Langmuir Isotherm Models by Zn-Cr- PW LDHs . Zn-Cr- SiW LDHs . Where qe and qt are capacities of adsorbed . at equilibrium and t is contact time . , k1 is the rate constant of PseudoFirst-Orde. Then, k2 is the rate constant of pseudo-second-order. He calculated kinetics parameters for rhodamine B (RhB) by Zn-Cr-PW and Zn-Cr-SiW LDHs are given in Table 1. It shows that of the two models kinetic equations, the PSO model is more fit than PFO based on the correction coefficient R2 . 2 Adsorption Isotherm and Thermodynamic Study Fig. 4 showed initial concentration vs concentration adsorbed with varying temperature of rhodamine B (RhB) adsorption by ZnAeCrAe SiW and Zn-Cr-PW LDHs. In Fig. Dyes adsorbed are higher at high temperature . K) its means the interaction of adsorbate-adsorbent is much stronger than solvent-adsorbent at adsorption sites. Fig. 4 when adding rhodamine B (RhB) concentration of 70, 90 and 100 . g / L) LDHs has reached its saturation point. This is indicated dyes adsorption capacity of the double layer hydroxy material not experiencing a significant increase in capacity. The adsorption isotherms were studied, as this provides information about the surface properties of adsorbent, the adsorption behavior and the design of adsorption systems. the process of rhodamine B (RhB) further investigated. The equilibrium isotherm adsorption explains how the adsorbent interacts with the adsorbate and Langmuir models. The Langmuir adsorption A 2019 The Authors. model is established on the following hypotheses, uniformly energetic adsorption sites, monolayer coverage, and no lateral interaction between adsorbed molecules. Therefore, at equilibrium, a saturation point is reached where no further adsorption can occur. The basic assumption is that sorption takes place at specific homogeneous sites within the adsorbent. Once a dye molecule occupies a site, no further adsorption can take place at that site (Abdellaoui et al. , 2017. Aguiar et al. , 2013. Laipan et al. Its used equation as follows: yayce/ycEyce = 1/. a yaycEycoycayc. /ycEycoycayc. where Ce is the concentration of adsorbate at equilibrium . g/L). Qe is the equilibrium adsorption capacity . qm is the maximum dye uptake for a complete monolayer . KL is the Langmuir constant (L/m. The basic features of the Langmuir equation can be expressed in terms of a separation factors RL which is a dimensionless constant defined as: ycIya = 1/. aya yayc. ) . where Ci is the initial concentration of rhodamine B (RhB) . g/L) and RL indicates the adsorption nature. When RL >1 the adsorption is unfavorable, while is linear if RL=1, favorable if Page 112 of 114 Science and Technology Indonesia, 4 . 109-114 Ramadhan et. Table 2. Langmuir Isotherm Models Parameter Langmuir Qmax . KL (L/m. T= 303 K Zn-Cr-PW T= 323 K Zn-Cr-SiW Zn-Cr-PW T= 343 K Zn-Cr-SiW 71,658 Zn-Cr-PW Zn-Cr-SiW Table 3. Values of Thermodynamic Parameters for The Adsorption of rhodamine B (RhB) T (K) Concentration . g/L) iS (J/mo. Zn-Cr-PW iH (J/mo. iG . J/mo. 0