Ammonium-Assisted Intercalation of Java Bentonite as Effective of Cationic Dye Removal

Modification of Java bentonite assists by the multi-step intercalation of sodium and ammonium ions under low-temperature preparation. The adsorbent was examined to remove rhodamine B and methylene blue dyes in an aqueous solvent. The analysis of structural changes conducted by XRD analysis showed the peak shifting from 19.89° to 16.1° and specific peak spectra FTIR of 2846.93 cm -1 due to increase basal spacing from ammonium intercalation. The total capacities of NH-bentonite, Na-bentonite, and Natural Bentonite adsorption to rhodamine B were 192.308 mg/g, 136.936 mg/g, and 116.279 mg/g, respectively, under acidic conditions. Furthermore, the total capacities of NH-bentonite, Na-bentonite, and Natural Bentonite adsorption to methylene blue were 270.27 mg/g, 158.73 mg/g, and 136.986 mg/g, respectively, under alkaline conditions. The adsorption mechanism described that the rhodamine B and methylene blue removal occurred endothermically, was feasible, and adhered to the kinetics model of pseudo-second-order and Langmuir isotherm. It concluded that the modified Java Bentonite from multi-step intercalation is affordable and effective as wastewater treatment .


INTRODUCTION
Contamination of the aquatic ecosystem has become an urgent concern due to the accumulation of pollutant inside it. Dye waste plays a large role in product coloring which pollutes in wide-area of the aquatic ecosystem due to annually discharged without proper treatment by industries (Tkaczyk et al., 2020). The complex structure of dye waste triggers accumulation in the environment and is difficult to degrade with traditional treatment (Khattab et al., 2020; Mahmoudabadi et al., 2019). The cationic dyes are extensively used in the coloringneeded industry, especially rhodamine B (RhB) and methylene blue (MB) with the structure shown in Figure 1 (Gupta et al., 2004;Rochkind et al., 2014). Naturally, the group of cationic dyes that classes to thiazine (for RhB) and xanthate (for MB) are considered more toxic due to their positive charge that easily interacts with organic life cells (Gillman, 2011;Inyinbor et al., 2015).
Nowadays, innovations in treatment techniques and materials include cation/anion exchange (Pai et al., 2021), biodegradation (Varjani et al., 2020), chemical coagulation (Iwuozor, 2019), catalyst reduction (Menon et al., 2021), adsorption (Rápó et al., 2020), and hybrid materials are proposed (Imgharn et al., 2022). Adsorption was established as a favorable technique because of its simplicity, low cost, and effectiveness (Crini, 2006;Yang et al., 2022). Popular adsorbents that are generally used include activated carbon, graphene, zeolites, polymers, layered double hydroxides, and clay-bentonite (Funes et  Natural material improvement has been raised as an urgent research topic for obtaining an eco-friendly material for wastewater treatment. Recently, raw materials from household wastes, agricultural products, industrial waste, marine materials, and soil are transformed to obtain an effective adsorbent (Pourhakkak et al., 2021). Bentonite is included in the clay mineral in the soil structure and is abundant in nature. Clay minerals are classified based on their minerals, including sepiolite (Gao et al., 2022), palygorskite (Câmara et al., 2020), zeolite (Sudibandriyo & Putri, 2020), kaolinite (Şenol et al., 2022), and bentonite . Bentonite is a type of smectite multilayer of octahedra alumina-silica tetrahedra which consist of montmorillonite mineral and others. The space between the layers contains exchangeable cations, including Cu 2+ , Mg + , Na + , K + , and others, thus usually improving into multifunctional material, especially adsorbent ( This work focused on bentonite modification by multi-step intercalation under low temperatures preparation assisted by sodium and ammonium ions. Bentonite-modified was examined as dyes waste removal in the case of RhB and MB. The mechanism of adsorption was analyzed by the following parameters: the pH effect, adsorption time, kinetics, isotherm, and thermodynamics adsorption. Furthermore, the conformed bentonite adsorbent prepared and modified based on the natural ambiance was proposed as an economical adsorbent in wastewater management.

Chemical and instrumentation
The specific Java Bentonite was purchased from Bentonit Makmur Sentosa Company in East Java of Indonesia with further treatment (sundried for 1 hour and filter-sieved in 200 mesh). The chemicals are Sigma Aldrich production in pure grade used without prior purification: sodium chloride (NaCl), ammonium chloride (NH 4 Cl), hydrochloric acid (HCl), sodium hydroxide (NaOH), distilled water, rhodamine B, and methylene blue. The characterization was conducted by using X-Ray Rigaku Miniflex-600 Diffractometer, FT-IR Spectrophotometer type Shimadzu Prestige-21, and UV-Visible Bio-base Spectrophotometer BKUV1800PC.

Bentonite intercalation
The Java Bentonite intercalated was prepared in steps: 100 g of bentonite was homogenized in 333 mL of saturated NaCl at 25 °C for 120 minutes, then dissolved in aqua solvent (the ratio of the mixture and solvent is 1:2, respectively) for 10 minutes. The mixture was filtered; then, the bentonite was re-homogenized in 333 mL of saturated NaCl at 25 °C for 120 minutes. The bentonite residue was washed using boiled water three times, then oven-dried at 200 °C for 12 hours. The product was named Na-bentonite.
In further steps, the 50 g of Na-bentonite was homogenized in 165 mL of saturated NH 4 Cl at 25 °C for 120 minutes and dissolved with aqua solvent (the ratio of the mixture and solvent is 1:2, respectively) for 10 minutes. The deposits were filtered and re-homogenized in 165 mL of saturated NH 4 Cl at 25 °C for 120 minutes. The deposit materials were washed three times using boiled water and oven-dried at 200 °C for 12 hours. The product was named NH-bentonite.

Adsorption work
Several parameters were examined as the effect of pH variation and the adsorption time by varying the pH adsorbate of 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11, then the adsorption time of 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, and 150 minutes. The adsorption process was started by mixing 50 mg/L dye solution with 0.02 g adsorbent in the beaker. The sample concentration after adsorption was analyzed by UV-Visible spectrophotometer using the specific wavelength of RhB at 555 nm and MB at 665 nm. Furthermore, the effects of temperature and initial concentration of adsorption were studied by varying the temperature of 30, 40, 50, 60, and 70 ℃, then the initial concentration for RhB of 50, 75, 100, 125, and 150 mg/L and for MB of 250, 255, 260, 265, and 270 mg/L (the different range due to effectiveness dye adsorption according to the preliminary trial).

Mechanism adsorption analysis
The quantity of RhB and MB adsorbed is calculated by the formula: where: q t -the total of sample adsorbed at a specific time (mg/g); C 0 and C t -sample concentration at initial and specific time adsorption (mg/L); v -the volume of sample adsorption (mL); m -the amount of adsorbent (g).
The kinetic adsorption was analyzed by pseudofirst-order (PFO) (2) and pseudo-second-order (PSO) (3) models that were determined by the formula: where: q t and q e -the total of sample adsorbed at a specific time and equilibrium phase (mg/g); K 1 -the adsorption rate constant of the PFO models (min -1 ); K 2 -the adsorption rate constant of the PSO models (min -1 ).
The isotherm adsorption models were conducted to Langmuir (4) and Freundlich (5) models that were determined by the formula: where: C e -the sample concentration in the equilibrium phase (mg/L); q e and q max -the total of sample adsorbed at the equilibrium phase and maximum condition (mg/g); K L -the constant of Langmuir adsorption (mg/L); K f (L/g) and n -the constant of Freundlich adsorption.
The thermodynamic adsorption was measured by the formula: where: K d -the adsorption distribution coefficient; C t -sample concentration at the equilibrium phase (mg/L); q e -the quantity of sample adsorbed at the equilibrium phase (mg/g); R and T -the gas constants and absolute temperature (K).

RESULT AND DISCUSSION
The Bentonite-intercalated diffraction patterns displayed in Figure 2 showed that intercalation has changed the structure of Java Bentonite. Bentonite belongs to the smectite group with dominancy of montmorillonite minerals, which is confirmed by the reflections of 2θ around 5°, 20°, 35°, and 62° (Mao et al., 2021;Taher et al., 2018). Furthermore, the quartz minerals were detected at 26°, then feldspar reflections at 28° (Kumar & Lingfa, 2020).
The decreased impurities from quartz minerals are indicated by the decreased peak of 26° due to the different binding forces of NH 4 + intercalant at NHbentonite in Figure 2c    The pH dyes were controlled by the range of 2-11 to achieve the optimum condition. On the basis of Figure 4, the equilibrium adsorption    Figure 6. The trend of initial concentration and temperature variation on the adsorption of RhB (a, b, and c, respectively) and MB (d, e, and f, respectively) Using Natural Bentonite, Na-bentonite, and NH-bentonite on Natural Bentonite, Na-bentonite, and NHbentonite are compared to the pure dye concentration before adsorption with the optimum pH adsorption on RhB 2, 2, and 3, respectively, then the optimum pH adsorption on MB 9, 8, and 11, respectively. According to Ribeiro dos The time variation was analyzed to determine the equilibrium state of the kinetics adsorption models. Figure 5 shows the kinetic adsorption parameter of Natural Bentonite, Na-bentonite, and NH-bentonite on adsorption of RhB (a, b, and c) and MB (d, e, and f), the equilibrium state of the adsorption occurs at 100 minutes. The analysis of kinetics adsorption models was supported by the data in Table 1 and it can be concluded that the adsorption process of bentonite-intercalated adsorbent the pseudo-second-order (PSO) model  indicated by the value of R 2 which is closer to 1.
The pseudo-second-order models describe that adsorption occurs due to the interaction of adsorbent and adsorbates by chemisorption mechanism (Shattar & Foo, 2022; Toor & Jin, 2012). Furthermore, Figure 6 shows the data support of the removal ability by the adsorbent based on the data variation of temperature and concentration.
On the basis of the data of initial concentration and temperature variation on the adsorption of RhB and MB, it was confirmed that increasing temperature adsorption generated an increase in concentration adsorption. The highest adsorption capacity occurs at the temperature of 70 °C. Table 2 explained the analysis of isotherm adsorption parameters, the highest adsorption capacity of RhB and MB were reached by NH-bentonite with the value 192.308 mg/g and 270.270 mg/g, respectively. The adsorption process has adhered to the Langmuir isotherm equation, confirmed by the R 2 value being closer to 1 (Chopra et al., 2012;Siregar et al., 2021). The Langmuir model described that the adsorption process was triggered by specific interaction between active site adsorbent to adsorbate and occurs in monolayer adsorption (Jović-Jovičić et al., 2008).
The analysis of thermodynamic adsorption of RhB and MB are shown in Tables 3 and 4, respectively. The adsorption using Natural Bentonite, Na-bentonite, and NH-bentonite was generated in the spontaneous condition that was indicated by negative values of Gibbs energy  This work is a proposed innovation to obtain a bentonite-based adsorbent that is effective on cationic dyes removal. Herethe comparison between the adsorption capacity of this work's adsorbent and another work's adsorbent is shown in Table 5. Table 5 confirms that the maximum adsorption capacity of NH-bentonite to RhB and MB in this study is greater than that of the adsorbents shown in Table 5.

CONCLUSIONS
The Java Bentonite modified by multi-step intercalation assisted by sodium and ammonium ions as intercalant under low-temperature preparation increased the basal spacing supports by the XRD analysis of increased basal spacing indicated by a shift of 2θ from 19.89° to 16.1°. Under the optimum conditions of the acidic pH, the capacity of NH-bentonite, Na-bentonite, and Natural Bentonite adsorption to RhB reach 192.308 mg/g, 136.936 mg/g, and 116.279 mg/g, respectively, then under the alkaline conditions, the capacity of NH-bentonite, Na-bentonite, Natural Bentonite adsorption to MB reach 270.27 mg/g, 158.73 mg/g, and 136.986 mg/g, respectively.