Title Science and Technology Indonesia e-ISSN:2580-4391 p-ISSN:2580-4405 Vol. 7, No. 2, April 2022 Research Paper Mg/Al-chitosan as a Selective Adsorbent in The Removal of Methylene Blue from Aqueous Solutions Patimah Mega Syah Bahar Nur Siregar1, Aldes Lesbani2, Risfidian Mohadi3* 1Magister Programme Graduate School of Mathematics and Natural Sciences, Sriwijaya University, Palembang, 30139, Indonesia2Research Center of Inorganic Materials and Complexes, Faculty of Mathematics and Natural Sciences, Sriwijaya University, Palembang, 30139, Indonesia3Graduate School of Faculty Mathematics and Natural Sciences, Sriwijaya University, Palembang, 30139, Indonesia *Corresponding author: risfidian.mohadi@unsri.ac.id AbstractThe use of dyes in the textile industry is detrimental to aquatic biota and humans. Pollution caused by dye waste can be overcomeby adsorption methods using adsorbents such as LDH. LDH is known as an adsorbent that is often found in the process of removingdye waste, but repeated use is not effective. This can be overcome by the LDH modification process using a supporting material suchas chitosan. Modification of LDH can be done using coprecipitation or precipitation simultaneously at pH 10. XRD analysis where thepeaks that appear in Mg/Al-chitosan are similar to the typical peaks of the constituent materials, namely Mg/Al and chitosan. This isconfirmed by FTIR analysis where the spectrum that appears in Mg/Al-chitosan is similar to the spectrum in Mg/Al and chitosan. Aswell as BET analysis where there is an increase in the surface area of Mg/Al after being modified to Mg/Al-chitosan from 5.845 m2/gto 24.556 m2/g. In this study, the selectivity process for the dye mixture was carried out first with the most selective dye for theMg/Al-chitosan adsorbent was methylene blue. Methylene blue was continued for adsorption processes such as isotherm adsorptionkinetics and adsorption thermodynamics as well as adsorbent regeneration studies. The results showed that at 90 minutes theadsorption reached equilibrium. The adsorption capacity of Mg/Al increased after modification using chitosan from 84.746 mg/gto 108.696 mg/g. The adsorption process follows the Langmuir isotherm type where adsorption occurs chemically (monolayer).Regeneration studies show that Mg/Al-chitosan is an adsorbent that can be used repeatedly with stable adsorption effectivenessuntil the fifth cycle. KeywordsAdsorption, Selectivity, Methylene Blue, Regeneration Received: 4 November 2021, Accepted: 23 February 2022 https://doi.org/10.26554/sti.2022.7.2.170-178 1. INTRODUCTION Theincreasinguseofdyes invarious industries suchas foodand textiles can cause serious environmental problems. Disposal of large volumes of waste into the environment causes adverse eects on aquatic ecosystems and human life. This pollution will reduce the quality of the waters so that the biota living in the aquatic environment will also be threatened. This problem is getting worse because the dye is biologically dicult to de- compose, so the polluted dye must be reduced in concentration and removed from the aquatic environment (El-Mekkawi et al., 2016). One of the synthetic dyes that are harmful to health is methylene blue. Methylene blue (MB) is a basic dye that is relatively cheap compared to other dyes, so it is often used in chemistry, biology, medicine, and the coloring industry (Sagita et al., 2021). Methylene blue (Figure 1) is a cationic dye that is soluble in water. These dyes may cause eye irritation and skin, systemic eects including blood changes. In addition, exposure to methylene blue at certain levels can cause vomiting, nausea, diarrhea, dizziness, excessive sweating, and digestive inammation (Wei et al., 2015). Figure 1. Methylene Blue (MB) The negative impact of the use of dyes resulted in dye https://crossmark.crossref.org/dialog/?doi=10.26554/sti.2022.7.2.170-178&domain=pdf https://doi.org/10.26554/sti.2022.7.2.170-178 Siregar et. al. Science and Technology Indonesia, 7 (2022) 170-178 waste being processed rst before being discharged into the environment (Kulkarni and Kaware, 2014). Wastewater treat- ment aims to eliminate or reduce the content of dissolved and dispersed pollutants in the wastewater solution. One way that can be done to treat wastewater is by adsorption (Alagha et al., 2020). Adsorption is a physical method that is widely used to treat waste because it is easy, ecient, and can use various types of adsorbents (Xu et al., 2021). One of the adsorbents that can be used to absorb dyes is layered double hydroxide (LDH) (Zubair et al., 2018). LDH is a material consisting of a positively charged layer of 2-dimensional (2D) brucite. The presence of a network of hydrogen bonds between LDH layers results in the accumu- lation of layers, resulting in LDH in bulk form which has a 3-dimensional (3D) character. LDH has unique characteristics such as being easy to synthesize, having anions between layers that are easily exchanged, and having a large surface area (Xu et al., 2021). LDH also has a positive total charge so it is often used as an adsorbent (Benicio et al., 2015). LDH have the general formula: [M2+1-xM3+x(OH)2]x+(An-)x/n.nH2O where M2+ and M3+ are two and three valent metals, n is the mole fraction M3+/(M3++M2+) and A are balancing anions between layers (Karami et al., 2019). The coprecipitation method can be used in the LDH synthesis process. The ratio used is 3:1 (M2+:M3+) because LDH is known as a hydrotalcite material. The eectiveness and eciency of the material are the ba- sis for selecting the use of a particular material. Besides the abundance of quality products, there is also a large buildup of chemical waste. The need to reuse and recycle materials such as composites is one of the best solutions. LDH has poor structural stability so it is necessary to modify LDH to produce composites. Modication of LDH can be done using graphene (Vinsiah et al., 2020), humic acid (Li et al., 2020a), biochar (Huangetal.,2019),hydrochar(Jungetal.,2021), andchitosan (Siregar et al., 2021a). Chitosan is a derivative of chitin with the structure [𝛽- (1→4)-2-amine-2-deoxy-D-glucose] (Zeng et al., 2015). Chi- tosan is a type of cationic polysaccharide biosorbent (Zhang et al., 2020). LDH has a less than optimal ability in the ab- sorption process of cationic species so it is necessary to modify LDH with chitosan. The advantages of chitosan such as hav- ing NH2 and OH functional groups that can help increase the absorption of cationic species because there will be interac- tions between the functional groups in chitosan and functional groups in cationic species such as methylene blue. Siregar et al. (2021a) reported thatMg/Al-chitosanwasable toadsorbcongo red dye with a maximum capacity of 344.828 mg/g. Research conducted byKhalili et al. (2021) reported that MnFe/chitosan showed a non signicant decrease for four consecutive cycles of sunset yellow (SY) dye removal of 94.23%, 85.87%, 79.26%, and 61.98%, respectively. In this study, modication of LDH using chitosan aims to increase the surface area of the material so that the adsorp- tion capacity obtained also increases, that the structure of the material is more stable so that it can be used repeatedly in the process of removing methylene blue dye in water. The synthesized materials were characterized using XRD, FTIR, and BET analysis. In this study, the selectivity of a mixture of various dyes was carried out to determine the most selective dyestu. The most selective dyes for each adsorbent will be subjected to adsorption studies including kinetic, isotherms, and thermodynamics, as well as adsorbent regeneration studies. 2. EXPERIMENTAL SECTION 2.1 Chemicals and Instrumentation The materials used in this study were Mg(NO3)2.6H2O (EM- SURE r), Al(NO3)3.9H2O (Sigma-Aldrich), chitosan extract ed from shrimp shells, NaOH, distilled water, nitrogen, rhoda mine-B (Rh-B), malachite green (MG), and methylene blue (MB). The synthesized material was characterized using X- Ray Rigaku Miniex-6000, FTIR by Shimadzu Prestige-21, and Adsorption–desorption N2 analysis was performed using a Quantachrome Micromeritics ASAP surface area and poros- ity analyzer, as well as adsorption analysis using UV-Visible Bio-Base spectrophotometer BK-UV1800. 2.2 Synthesis of Mg/Al The coprecipitation method with molar ratio (3:1) was used in the synthesis of Mg/Al-NO3 LDH. Mg(NO3)2.6H2O (19.230 g, 100 mL) and Al(NO3)3.9H2O (9.378 g, 100 mL) were mixed and the pH was adjusted to 10 using 2 M NaOH. The mixture was stirred at 80°C for 17 hours and was used in at- mospheric nitrogen conditions to minimize the formation of Mg/Al-CO3 in the synthesis process. After 17 hours, the pre- cipitate was ltered, rinsed, and dried. Materials were charac- terized using XRD, FTIR, and BET analysis. 2.3 Extraction of Chitosan Demineralization and deproteination processes were carried out to extract shrimp shells. Shrimp shells were crushed and put into a beaker, then 1 M HCl was added in a ratio of 1:10 (w/v). The mixture was stirred at 60°C for 3 hours. After the stirring is complete, the precipitate is ltered and dried. After the demineralization process is complete, it is followed by the deproteination process. The residue from the demineralization process was put into a beaker and 0.1 M NaOH was added in a ratio of 1:10 (w/v). The mixture was stirred at 60°C for 1 hour. After 1 hour, the precipitate was ltered and dried in the oven. The chitosan obtained was characterized using XRD, FTIR, and BET to prove the success of extracting chitosan from shrimp shells. 2.4 Preparation of Mg/Al-chitosan 60mLofamixtureofMg(NO3)2.6H2OandAl(NO3)3.9H2O solutions were stirred for 1 hour and the pH was adjusted to 10 using NaOH. After 1 hour, 3 g of chitosan was added to the mixture. Stirring was continued for up to 72 hours at 80°C. After completion, the precipitate was ltered, rinsed, and dried for characterization using XRD, FTIR, and BET analysis. © 2022 The Authors. Page 171 of 178 Siregar et. al. Science and Technology Indonesia, 7 (2022) 170-178 2.5 Selectivity Dyes (Rhodamine-B, Malachite Green, and Methylene Blue) 20 mg/L of each dye as much as 20 mL was added with 0.02 g of adsorbent. The mixture is stirred according to the predeter- mined contact variation. After the stirring was completed, the ltrate was measured at 500-700 nm using a UV-Visible spec- trophotometer. The dye with the largest adsorption capacity is used in the next adsorption process. 2.6 Eect of Adsorption Contact Time 100 mg/L methylene blue (20 mL, 0.02 g adsorbent) adjusted the pH according to the optimum pH of methylene blue. The mixture was stirred according to variations in contact time (0, 5, 20, 30, 60, 90, 120, 150, 180, and 200 minutes) and the ltrate was measured using a UV-Visible spectrophotometer. 2.7 Eect of Concentration and Temperature Variations in the initial concentration of methylene blue and variations in adsorption temperature were carried out to see the eect of isotherm and adsorption thermodynamics. The initial concentration variations (60, 70, 80, 90, and 100 mg/L) were 20 mL and 0.02 g of adsorbent was added. The mixture was stirred for 2 hours and using various temperatures (30, 40, 50, and 60°C). After 2 hours, the ltrate was measured using a UV-Visible spectrophotometer at a wavelength of methylene blue (664 nm). 2.8 Regeneration of Adsorbent The regeneration process was carried out by adsorption of MB dye (100 mg/L, 25 mL) and adding 0.1 g of adsorbent. The solution was stirred and the ltrate was measured using a UV-Visible spectrophotometer. The adsorbate bound to the adsorbent will be released by a desorption process using an ultrasonic system, then the adsorbent is dried using an oven. The same treatment was carried out for the next cycle. 3. RESULTS AND DISCUSSION Figure 2(a) shows the diraction pattern of Mg/Al where peaks appear at angles 11.47°(003), 22.86°(006), 34.69°(009), and 61.62°(110), the results obtained are similar to JCPDS data No. 22-700. Figure 2(b) shows the diraction pattern of chitosan where peaks appear at an angle of 7.93°(003) and 19.35°(002) as reported by Mohadi et al. (2022) that the diraction pattern of chitosan appears at an angle of 9.49°(001) and 19.59°(002). Peaks that appear at angles 10.83°(003), 19.52°(006), and 60.6°(110) indicates that Mg/Al-chitosan has a characteris- tic peak from each of its constituent materials, namely LDH and chitosan. This indicates that the Mg/Al-chitosan synthesis process was successful (Figure 2(c)). Figure 3(a) shows the results of the FTIR analysis of Mg/Al which appears at 3500 cm−1 indicatingOH vibrations from wa- ter molecules and at 1635 cm−1 stretching vibrations from OH occur. The N-O group from nitrate appears at a wavenumber of 1381 cm−1. The peak that appears at 748 cm−1 indicates the presence of M-O vibrations. Figure 3(b) shows the spectrum Figure 2. XRD Patterns of Mg/Al (a), Chitosan (b), and Mg/Al-chitosan (c) Figure 3. FTIR Spectra for Mg/Al (a), Chitosan (b), and Mg/Al-chitosan (c) of chitosan, where the strain vibrations of the NH2 and OH groups occur at 3447 cm−1. Spectrums that appeared at 1652 cm−1 and 1566 cm−1 indicated the presence of CONH2 and NH2 from chitosan. Figure 3(c) shows the results of Mg/Al- chitosan where the spectrum that appears at 1381 cm−1 is the vibration of the nitrate anion from LDH and the spectrum at 3447 cm−1 shows the strain of NH2 and OH groups from chitosan (Mohadi et al., 2022). Important factors aecting the quality of the adsorbent are surface area, pore volume, and pore size. Analysis to determine surface area, pore volume, and pore size can be done using the BET method. BET theory is based on the adsorption process using the principle of adsorption isotherm (Langmuir © 2022 The Authors. Page 172 of 178 Siregar et. al. Science and Technology Indonesia, 7 (2022) 170-178 Table 1. BET Analysis of Materials Materials Surface Area Pore Volume Pore Size (m2/g) (cm2/g) BJH (nm), BJH Mg/Al 5.845 0.017 17.057 Chitosan 8.558 0.018 16.983 Mg/Al-chitosan 24.556 0.031 3.169 Table 2. Kinetic Parameter Adsorbent Initial Concentration Qeexp PFO PSO (mg/L) (mg/g) Qecalc (mg/g) R 2 k1 Qecalc (mg/g) R 2 k2 Mg/Al 100.608 40.919 10.044 0.901 0.032 41.322 0.999 0.012 Chitosan 100.608 45.421 1.262 0.901 0.023 45.455 0.999 0.057 Mg/Al- chitosan 100.608 46.877 2.757 0.922 0.037 46.948 0.999 0.029 Figure 4. BET Prole of Mg/Al (a), Chitosan (b), and Mg/Al-chitosan (c) theory). In the adsorption process, the system that occurs is gas- solid. Gases are adsorbed (adsorbate) and solids are adsorbents (adsorbent). The pore size of the adsorbent will be determined bythe amount of gas absorbed. Based on the results of the BET analysis, the data obtained are as shown in Table 1. The surface area of Mg/Al is 5.845 m2/g, the surface area of chitosan is 8.558 m2/g, and the surface area of Mg/Al-chitosan has increased to 24.556 m2/g. Figure 4 shows the adsorption- desorption pattern of each adsorbent following Type IV where the adsorption isotherm on mesoporous adsorbents with strong and weak anities (Siregar et al., 2021b). Figure 5 shows the selectivity of a mixture of rhodamine-B (Rh-B), malachite green (MG), and methylene blue (MB) dyes. In Figure 5, it can be seen that the longer the time used, the more signicant the decrease in absorbance for MB dye. At Figure 5. Selectivity of Rh-B, MG, and MB onto Mg/Al (a), Chitosan (b), and Mg/Al-chitosan (c) 90-120 minutes it shows that there is an insignicant decrease in MB, this indicates that at 90-120 minutes MB has been in equilibrium. Figure 6 shows a graph of the eect of contact time on the adsorption of methylene blue by the adsorbent, where the longer the adsorption contact time, the greater the methylene blue adsorbed. The results showed that each adsorbent opti- mally adsorbed methylene blue at 90 minutes, but if it is too long it can reduce the absorption rate. The longer the contact time can also lead to desorption, namely the release of dye © 2022 The Authors. Page 173 of 178 Siregar et. al. Science and Technology Indonesia, 7 (2022) 170-178 Table 3. Isotherm Adsorption Adsorbent Adsorption Adsorption 303KIsotherm Constant Mg/Al Langmuir Qmax 84.746 kL 0.017 R2 0.7454 Freundlich n 2.05 kF 13.527 R2 0.6056 Chitosan Langmuir Qmax 89.286 kL 0.018 R2 0.9862 Freundlich n 1.458 kF 7.525 R2 0.5047 Mg/Al-chitosan Langmuir Qmax 108.696 kL 0.36 R2 0.8959 Freundlich n 2.181 kF 18.655 R2 0.6207 Figure 6. Variation of Adsorption Contact Time that has been bound by the adsorbent. Bernard and Jimoh (2013) showed that after the adsorption reached equilibrium at the optimum contact time, the further addition of contact time between the adsorbent and the adsorbate did not have a signicant eect on the absorption of the dye. The determination of the equilibrium model depends on the value of the correlation coecient (R2). A suitable equi- librium model is an equilibrium model with a value of (R2) that is higher or closer to 1 (Seedao et al., 2018; Juleanti et al., 2021). The value of the correlation coecient (R2) of the sec- Figure 7. Eect of Initial Concentration and Adsorption Temperature of Mg/Al (a), Chitosan (b), and Mg/Al-chitosan (c) ond order is closer to one (1) than the rst order. If the value of (R2) in pseudo rst order (PFO) is greater and closer to the value of 1 then the adsorption involves a physical reaction and if the value of (R2) in the pseudo second order (PSO) is greater and closer to the value of 1 then the adsorption involves © 2022 The Authors. Page 174 of 178 Siregar et. al. Science and Technology Indonesia, 7 (2022) 170-178 Table 4. Thermodynamic Adsorption Adsorbent T (K) Qe ΔH ΔS ΔG (mg/g) (kJ/mol) (J/mol K) (kJ/mol) Mg/Al 303 41.416 16.487 0.061 -1.873 313 43.053 -2.479 323 45.237 -3.085 333 48.208 -3.691 Chitosan 303 44.6 12.669 0.05 -2.558 313 45.843 -3.06 323 47.238 -3.563 333 49.36 -4.065 Mg/Al-chitosan 303 49.572 31.703 0.117 -3.694 313 51.756 -4.862 323 54.211 -6.03 333 56.394 -7.198 Table 5. Adsorption Capacity using Several Adsorbents Adsorbent Adsorption ReferenceCapacity (mg/g) Chitosan/zeolite Composite 24.51 (Dehghani et al., 2017) H2SO4 Cross-linked Magnetic 20.41 (Rahmi and Mustafa, 2019) Chitosan Nanocomposite Beads Fe3O4 Activated Montmorillonite 106.4 (Chang et al., 2016) Nanocomposite Chitosan Resin 11.3 (Buaphean et al., 2017) Chitosan 11.04 (Moosa et al., 2016) Activated Lignin Chitosan 36.25 (Albadarin et al., 2017) N,O-carboxymethyl Chitosan 1.14 (Sulizi and Mobarak, 2020) Ultrasonic Surface Modied Chitin 26.69 (Dotto et al., 2015) Carbon Physical Activation 15.553 (Khuluk, 2019) Dried Cactus (DC) 14.045 (Sakr et al., 2020) Natural Cactus (NC) 3.435 (Sakr et al., 2020) Chitosan/organic Rectorite-Fe3O4 24.69 (Zeng et al., 2015) Natural Zeolite 21.189 (Ngapa and Gago, 2021) Micro Cellulose Fibrils 54.9 (Kankilic and Metin, 2020) Rice Husk 25 (Patil et al., 2017) Mg/Al 84.746 This Work Chitosan 89.286 This Work Mg/Al-chitosan 108.696 This Work a chemical reaction (Wang et al., 2013). The adsorption rate data in Table 2 shows that the PSO model provides a more presentable model of the adsorption rate, the second-order equation is based on the assumption that adsorption involves a chemical process between the adsorbent and the adsorbate (Hamzezadeh et al., 2022). The adsorption isotherm was determined to determine the relationship between the concentration of the adsorbed sub- stance (adsorbate) and the amount absorbed at a constant tem- perature. There are two types of isotherms commonly used to determine the type of adsorption, namely the Langmuir isotherm and the Freundlich isotherm (Seedao et al., 2018). The determination of the Langmuir isotherm is done by mak- ing a relationship curve between Ce and Ce/Qe, so that the Ce versus Ce/Qe curve is obtained. While the determination of the Freundlich isotherm is done by making a curve of the relationship between log Ce and log Qe (Amtul et al., 2018). Figure 7 shows a linearization graph for the adsorption of each adsorbent on methylene blue. This is indicated by the value of the linear regression coecient (R2) on the Langmuir © 2022 The Authors. Page 175 of 178 Siregar et. al. Science and Technology Indonesia, 7 (2022) 170-178 isotherm is greater than the Freundlich isotherm so that the adsorption pattern that occurs on each adsorbent with methy- lene blue dye is monolayer with the Langmuir isotherm model (Zhang et al., 2020). The adsorption capacities of Mg/Al, chi- tosan, and Mg/Al-chitosan were 84.7466 mg/g, 89.286 mg/g, and 108.696 mg/g as shown in Table 3. The results showed that Mg/Al-chitosan was the most eective adsorbent to absorb MB. Figure 8. Regeneration of Mg/Al (a), Chitosan (b), and Mg/Al-chitosan (c) Figure 9. Adsorption Mechanism of Methylene Blue using Mg/Al-chitosan Thermodynamic parameters are needed to provide infor- mation related to the direction and changes in internal energy that occur during the adsorption process of methylene blue with the adsorbent including the enthalpy change (ΔH) (Ge and Du, 2020), the entropy change (ΔS) (Ali et al., 2020), and the Gibbs free energy change (ΔG) (Zhu et al., 2012; Mohadi et al., 2022). Based on Table 4, it can be seen that the energy released during the methylene blue adsorption process is highly dependent on the type of adsorbent interaction. The positive enthalpy parameter value (ΔH) stated in Table 4 indicates that the adsorption process of methylene blue occurs endothermic where the adsorption capacity at the same initial concentra- tion increases with increasing temperature (Li et al., 2020b). The small entropy value (ΔS) indicates that the distribution of methylene blue on the adsorbent surface is very regular with a small entropy value (Patil et al., 2017). The value of Gibbs free energy (ΔG) is negative, indicating that the adsorption process of methylene blue takes place spontaneously (Wang et al., 2013). The regeneration process of the adsorbent aims to see the ability to reuse the adsorbent which will be used for the re- adsorption process. Regeneration aims to restore the function of the active site of the adsorbent so that it can bind the ad- sorbate again and there is a rearrangement of the groups of the adsorbent that have been used in the adsorption process. Figure 8 shows that Mg/Al and chitosan decreased drastically from cycles 3-5, while Mg/Al-chitosan showed an insigni- cant decrease in adsorption capacity from cycles 1 to 5. This indicates that Mg/Al-chitosan is an eective adsorbent used repeatedly in the process of removing MB dye from water. TheadsorptionmechanismofmethyleneblueusingMg/Al- chitosan is shown in Figure 9. Figure 9 shows the presence of functional groups of chitosan in the form of NH2 and OH bonded to methylene blue, thus the dye tends to bind more strongly to the OH group of chitosan, so that the binding of methylene blue on the adsorbent is more dominant in chem- ical adsorption, which is supported by the data. adsorption isotherm. A comparison of the adsorption capacity of methylene blue using various adsorbents is shown in Table 5. Table 5 shows that Mg/Al-chitosan in this study was able to adsorb methy- lene blue with the largest capacity compared to others, namely 108.696 mg/g. 4. CONCLUSION This study aims to modify the LDH using chitosan, as evi- denced by XRD analysis where the peaks that appear in Mg/Al- chitosan are similar to the typical peaks of the constituent mate- rials, namely Mg/Al and chitosan. This is conrmed by FTIR analysis where the spectrum that appears in Mg/Al-chitosan is similar to the spectrum in Mg/Al and chitosan. As well as BET analysis where there is an increase in the surface area of Mg/Al after being modied to Mg/Al-chitosan from 5.845 m2/g to 24.556 m2/g. In the dye selectivity process, MB tends to be more easily absorbed than Rh-B and MG. In this study, the adsorption process followed the Langmuir isotherm equation. The thermodynamic data showed that the adsorption process was endothermic, regular, and spontaneous. The regeneration processconrmedthatMg/Al-chitosan isaneectiveadsorbent for repeated use in the MB adsorption process. 5. ACKNOWLEDGEMENT All authors thanks to the Laboratory of Inorganic Materials and Complexes of the Faculty of Mathematics and Natural Sciences, Sriwijaya University for support of this research. © 2022 The Authors. Page 176 of 178 Siregar et. al. Science and Technology Indonesia, 7 (2022) 170-178 REFERENCES Alagha, O., M. S. 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Starch NiFe Layered Double Hydroxide Composites: Ecient Removal of Methyl Or- ange from Aqueous Phase. Journal of Molecular Liquids, 249; 254–264 © 2022 The Authors. Page 178 of 178 INTRODUCTION EXPERIMENTAL SECTION Chemicals and Instrumentation Synthesis of Mg/Al Extraction of Chitosan Preparation of Mg/Al-chitosan Selectivity Dyes (Rhodamine-B, Malachite Green, and Methylene Blue) Effect of Adsorption Contact Time Effect of Concentration and Temperature Regeneration of Adsorbent RESULTS AND DISCUSSION CONCLUSION ACKNOWLEDGEMENT