Metal Pillared Bentonite Synthesis and Its Characteristics Using X-Ray Diffraction

Modification of bentonite by the Al/Fe metal oxide pillarization process was carried out with metal oxides. The bentonite pillars were successfully characterized using an X-Ray Diffraction (XRD) spectrophotometer. The re sults of XRD characterization showed the peak diffraction angle (2 θ ) in metal-pillared bentonite was 26.84° at 698.98 cps. Meanwhile, in thermally and chemically activated bentonite, the peak angles were marked at 20.64° and 26.7°. There is a shift in the peak angle after activation and pillarization. XRD patterns showed dioctahedral smectite and quartz accessory minerals.


INTRODUCTION
Natural bentonite is a lamellar aluminosilicate mesoporous material with a crystal structure in which the interlayer space in the structure is occupied by replaceable cations, for example, Na + , K + , and Ca +2 (Elfadly et al., 2017). Bentonite contains varying amounts of silica with montmorillonite as the base mineral and other minerals, such as quartz, calcite, and feldspar. The characteristics of bentonite depend on the amount of smectite. The properties of smectite, namely cation exchange capacity, particle size, pore structure, adsorption properties, surface area and catalytic activity, are strongly influenced by thermal treatment (Andrini et al., 2017). Bentonite from smectite, especially montmorillonite (80-90 wt%), can expand several times its original volume when they come into contact with water, (Kumar and Lingfa, 2020). Calcium bentonite proved to be a catalyst for the pyrolysis of plastics (Panda, 2018). Although the crystal structure is different, the chemical composition of clay, feldspar and zeolite minerals are close (Özgüven et al., 2019).
Bentonite, a natural clay mineral with a layered structure, contains exchangeable inorganic cations (Andrunik and Bajda, 2019). The cations that can be exchanged, found in the structure of the bentonite layer, in addition to having the ability to expand, are also widely found in Indonesia. This is why this material is suitable for applications as adsorbents and catalysts (Goodarzi et al., 2016). However, bentonite has one drawback: a small distance between layers and unreliable Metal Pillared Bentonite Synthesis and Its Characteristics Using X-Ray Diffraction Sisnayati 1 , Muhammad Said 2 , Nabila Aprianti 3 , Ria Komala 1 , Hendra Dwipayana 4 , Muhammad Faizal 3* porosity. Modified clays can be divided into pillared layered clays, organoclays, nanocomposites, acid and salt-induced, and thermally and mechanically-induced modified clays (Motawie et al., 2014). Pillarization involves the insertion of ions, molecules or compounds in the bentonite interlayer (Wijaya et al., 2021). In this work, Al/ Fe macro-anions were used as the insertion material. In addition to being in the bentonite, thus making the distance between the layers farther apart, metal oxides are also on the surface of the bentonite. This research aims to synthesize natural metal pillared bentonite and compare its characteristics with bentonite, which is activated by heating and chemical.

Materials
The bentonite used in this study was categorized as natural bentonite purchased from Loba Chemie Pvt Ltd. The chemicals used to synthesize metal pillared bentonite consisted of H 2 SO 4 , Al(NO 3 ) 3 ·9H 2 O, Fe(NO 3 ) 3 ·9H 2 O, NaOH, and aquades (H 2 O).

Purification and activation of natural bentonite through chemical process
The bentonite was cleaned and weighed 5 g, placed into a 250 mL beaker, added 200 mL of 5% H 2 SO 4 , and stirred using a magnetic stirrer for 8 h at room temperature. Then, the mixture was separated using centrifugation and washed with distilled water several times to remove the remaining SO 4 2anions. The bentonite solid was dried in an oven at 80 °C for 8 h.

Bentonite activation by thermal process
Natural bentonite is activated by calcination at a temperature range of dehydroxylation. Catalyst preparation was carried out by activating heating using a muffle furnace at a temperature of 400 °C with a heating rate of 5 °C/min for 3 hours calculated after the desired temperature was reached.

Preparation of Al/Fe pillar solution
Al/OH polyhydroxy pillaring solution was prepared by adding 80 mL of 0.5M Al(NO 3 ) 3 ·9H 2 O into a 240 mL 0.5 M NaOH solution mixed in a 500 mL beaker. The Fe/OH pillar solution was prepared by adding 40 mL of 0.5 M Fe(NO 3 ) 3 ·9H 2 O mixed in a 500 mL beaker into 240 mL of 0.5 M NaOH solution. The Al/Fe pillar solution mixture was stirred for 2 h and then allowed to stand for 2 days at room temperature.

Characterization
The structural changes were analyzed using the X-Ray diffraction (XRD) method using the Rigaku Miniflex 600 X-Ray diffractometer with CuK radiation at 30 kV and 10 mA. The analysis was carried out at a scanning speed of 10 °/min at 2θ with a range of 5-80°.

Aluminum nitrate [Al(NO 3 ) 3 ]
The XRD pattern of Al(NO 3 ) 3 is presented in

XRD of Fe(NO 3 ) 3
The diffraction pattern of Fe(NO 3 ) 3 is shown in Figure 2. The characteristic sharp peaks of Fe(NO 3 ) 3 are seen at the diffraction angles of 20.28°, 54.66°, and 79.27°. At a diffraction angle of 2θ 20.28°, the peak intensity is 376.805 cps, at a diffraction angle of 2θ 54.66°, the peak intensity is 620.22 cps, and at a diffraction angle of 2θ 79.27°, the peak intensity is 740.66 cps. The diffraction angle is a special characteristic of Fe(NO 3 ) 3 material which produces the distance between cells at the sharpest peak (54.66°) is 2.8 Å. This XRD pattern  Figure 3 shows the diffraction pattern of natural bentonite. Sharp peaks of natural bentonite are seen at diffraction angles of 20.28° and 26.76°. The diffraction angle is observed at 20.28° with peak intensity of 555.891 cps, and at a diffraction angle of 2θ 26.76°, the peak intensity is 858.903 cps. The diffraction angle is a special characteristic of bentonite material which shows the presence of anions between the natural bentonite layers and results in the distance between cells at the sharpest peak (26.76°) 4.26 Å. The initial XRD

Characteristics of thermal and chemical activated and Al/Fe pillared bentonite samples
The peak position values of natural bentonite and metal pillared bentonite samples were analyzed from the standard peak position values associated with the Joint Committee for Powder Diffraction Standards (JCPDS).

Characteristics of thermal activated natural bentonite
Thermally activated bentonite was characterized using XRD. The diffraction pattern is shown in Figure 4. The sharp peak characteristic of pure bentonite is seen at the diffraction angles of 20.64° and 26.68°. In the diffractogram, the diffraction angle of 2θ 20.64° shows a peak intensity of 484.69 cps, and at a diffraction angle of 2θ 26.68°, it offers a peak intensity of 777.77 cps. The diffraction angle is a special characteristic of

Characteristics of chemical activated bentonite
Chemically activated bentonite was characterized using XRD. The diffraction pattern is shown in Figure 5. The sharp peak characteristic of pure bentonite is seen at the diffraction angles of 20.84° and 26.7°. At a diffraction angle of 2θ 20.84°, the peak intensity is 425.93 cps; at a diffraction angle of 2θ 26.7°, the peak intensity is 901.69 cps. The diffraction angle is a special characteristic of bentonite material which shows the presence of anions present between the natural bentonite layers and produces the distance between cells at the sharpest peak (26.7°).

Characteristics of Al/Fe pillared bentonite
Natural and chemical-modified bentonite is used directly or as an industrial feedstock in many areas, depending on its physicochemical properties (Hasanudin et al., 2022;Kar et al., 2019;Komadel, 2016). Al/Fe-pillared bentonite was characterized using XRD, as shown in Figure 6. The sharp peaks characteristic of pure bentonite was seen at diffraction angles of 20.92°, 26.84°, and 35.56°. The diffraction angle of 2θ 20.92° shows a peak intensity of 606.803 cps. At a diffraction angle of 2θ 26.84°, the peak intensity is 698.98 cps, and at a diffraction angle of 2θ 35.56°, the peak intensity is 588 cps. The diffraction angle is a special characteristic of bentonite material which shows the presence of anions between the natural bentonite layers and produces the distance between cells at the sharpest peak (26.84°).

CONCLUSIONS
The bentonite pillars were successfully characterized using an XRD spectrophotometer. The results of XRD characterization showed the peak diffraction angle (2θ) in metal-pillared bentonite was 26.84° at 698.98 cps. Meanwhile, in thermally and chemically activated bentonite, the peak angles were marked at 20.64° and 26.7°. The peak angle shifts after the bentonite is thermally, chemically activated, and polarized. Bentonite shows the presence of dioctahedral smectite and quartz minerals.