Volume 27
Issue 3 September Article 7
9-25-2023
Isolation of Lignin from Sugarcane Bagasse as an Adsorbent for Isolation of Lignin from Sugarcane Bagasse as an Adsorbent for Chromium Ion
Chromium Ion
Nila Tanyela Berghuis
Department of Chemistry, Universitas Pertamina, South Jakarta City 12220, Indonesia, [email protected]
Nurul Fitri Novianti
Department of Chemistry, Universitas Pertamina, South Jakarta City 12220, Indonesia Paramita Jaya Ratri
Department of Chemistry, Universitas Pertamina, South Jakarta City 12220, Indonesia
Follow this and additional works at: https://scholarhub.ui.ac.id/science Part of the Earth Sciences Commons, and the Life Sciences Commons Recommended Citation
Recommended Citation
Berghuis, Nila Tanyela; Novianti, Nurul Fitri; and Ratri, Paramita Jaya (2023) "Isolation of Lignin from Sugarcane Bagasse as an Adsorbent for Chromium Ion," Makara Journal of Science: Vol. 27: Iss. 3, Article 7.
DOI: 10.7454/mss.v27i3.1446
Available at: https://scholarhub.ui.ac.id/science/vol27/iss3/7
This Article is brought to you for free and open access by the Universitas Indonesia at UI Scholars Hub. It has been accepted for inclusion in Makara Journal of Science by an authorized editor of UI Scholars Hub.
Makara Journal of Science, 27/3 (2023), 217−226 doi: 10.7454/mss.v27i3.1446
217 September 2023 Vol. 27 No. 3
Isolation of Lignin from Sugarcane Bagasse as an Adsorbent for Chromium Ion
Nila Tanyela Berghuis
*, Nurul Fitri Novianti, and Paramita Jaya Ratri
Department of Chemistry, Universitas Pertamina, South Jakarta City 12220, Indonesia
*E-mail: [email protected]
Received October 18, 2022 | Accepted July 3, 2023
Abstract
The waste generated in metal coating and leather tanning industries contribute to water pollution owing to the use of Cr metal in production processes. The utilization of lignin from natural base materials in the form of bagasse can reduce unwanted waste from production processes and adsorb Cr ion waste. In this study, lignin was successfully isolated from bagasse waste and then carbonized and applied in Cr metal absorption. Lignin and lignin carbon as an absorbent were characterized using Fourier-transform infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The ability of bagasse lignin and carbon lignin to absorb Cr ion waste was evaluated by monitoring mass fluctuation, contact time, and pH. The optimal conditions for adsorption were determined as follows: 0.015 g, 90 min, and pH 6. The adsorption isotherm followed the Freundlich model, and the adsorption kinetics followed the pseudo-first-order model.
Furthermore, adsorption thermodynamics showed that the reaction proceeded spontaneously, and the disorder degree increased in the adsorption system.
Keywords: adsorbent, bagasse lignin, chromium ion, lignin isolation, sugarcane bagasse
Introduction
Water is an essential resource for sustaining life, which has led to its increasing demand. According to BPS Indonesia data from 2010 to 2020, the population has increased from 237.64 million to 270.2 million. Water quality can be affected by environmental issues, such as industrial activity and industrial waste dumped into rivers, lakes, and seas [1]. Water pollution occurs because of the waste generated by the metal coating and leather tanning industries due to the use of Cr metal in their production processes. The leather tanning industry uses 60%–70% chromium sulfate. The huge amount of Cr metal used in the production process results in abundant Cr ion waste. Therefore, to mitigate water pollution, the need for natural materials that can absorb Cr ions is crucial [2].
Sugarcane is a natural resource that is widely available in Indonesia. As per the data, the sugarcane plantations spanned over 420.15 thousand hectares in 2017 [3]. The largest use of sugar cane is in the sugar manufacturing industry, which produces solid, gas, and liquid wastes [4]. Most of the waste generated is a solid in the form of bagasse [5]. However, bagasse waste is currently used only as animal feed, and its potential is underexplored.
The large volume of bagasse generated from the sugar manufacturing industry can be reused, and its composition includes 50% cellulose, 25% hemicellulose,
and 25% lignin [6]. One of the ways to optimize bagasse waste and increase its selling value is to utilize its lignin content as an adsorbent of heavy ions. Lignin is one of the natural polymers abundantly present in the cell walls of terrestrial plants and acts as a binding agent for various fibrous materials. Lignin treated as a waste product in return poses severe environmental problems, and its presence in wastewater produces a detrimental effect.
Structural analysis revealed that lignin has a high molecular weight and a surface area of 180 m2/g, making its three-dimensional polymer structure (which involves different functional groups of hydroxyl, methoxy, and phenolic) suitable for heavy metal removal from wastewater [7, 8]. Albadarin et al. 2011, reported the ad- sorption of toxic Cr (VI) in water by alkaline lignin [9];
the results showed that the saturated adsorption amount of Cr (VI) on lignin was 31.6 mg/g, and the adsorption proceeded through an ion-exchange mechanism. Wu et al. [10] reported a maximum adsorption amount of 17.97 mg/g for Cr (III) by an alkaline lignin isolated from black liquor, and the adsorption followed an ion-exchange mechanism. In their study the isolated lignin was carbonized and applied as a Cr metal adsorbent [10].
Materials and Methods
Materials. Sugarcane bagasse was obtained from PT Indolampung Perkasa, 15% NaOH (aq), H2SO4 (aq) 5N, 0.1M HCl (aq). K2Cr2O7 p.a (Merck KGaA). All other
chemicals and reagents were of analytical grade and used without further purification.
Instrumentation. Thermo Scientific Genesis 10S was used for UV-vis spectroscopy, Thermo Scientific Nicolet iS5 was applied for Fourier transform infrared (FTIR) spectroscopy in the range of 400–4000 cm−1, and a Phenom Pro X was utilized for scanning electron microscopy (SEM) at 20x magnification.
Procedure
Isolation of lignin from sugarcane bagasse. Bagasse was baked in an oven at 50 °C for 4 h, dissolved in 80 °C hot water for 2 h (with a ratio of 1:10), and centrifuged in a tube at 2000 rpm for 10 min. At 90 °C, the solid was dissolved in 15% NaOH for 2 h. The black liquor solution was filtered and acidified with 5N H2SO4 to pH 2, and a precipitate was formed. Centrifugation was carried out for 20 min at 4500 rpm. The lignin precipitate was washed with water, dried in the oven, and stored [11].
Sugarcane bagasse lignin carbonization. Bagasse lignin was placed in a porcelain cup and heated at 500 °C in a furnace for 1 h under normal air. The porcelain cup containing lignin was then removed from the furnace and stored in a desiccator. The bagasse lignin carbon (BLC) was transferred to a closed vial [12].
Characterization of lignin. Bagasse lignin (BL) and lignin carbon was studied using Fourier-transform infra- red spectroscopy (FTIR) and Scanning Electron Micros- copy (SEM). FTIR spectroscopy was performed using platinum KBr at 400–4000 cm−1, and SEM measurements were taken at a magnification of 20x to see the morphology.
Adsorption capability test under mass variations. In this study, 15, 30, 45, 60, 75, and 90 mg of lignin were placed in Erlenmeyer flasks and 10 mL of Cr-metal solution at 60 ppm was added to each of them. The mixture was stirred in an incubator shaker at a speed of 250 rpm for 30 min. UV-vis spectroscopy was performed at a wavelength of 440 nm to measure the solution after filtration. The optimum mass was established for different contact times. The measurements were recorded and analyzed.
Test of adsorption ability under contact time variations. Lignin was weighed according to the optimum mass and transferred to an Erlenmeyer flask, followed by the addition of 10 mL of Cr-metal solution at 60 ppm concentration. The mixture was stirred using an incubator shaker at 250 rpm for 15, 30, 45, 60, 75, and 90 min. After filtration, the solution was measured using UV-vis spectroscopy at a wavelength of 440 nm. For pH
variations, the optimum contact time was adopted. The measurements were recorded and examined.
Test of adsorption ability under pH variations. The pH of the Cr solution was adjusted to 1–8 by adding 0.1- M HCl or 0.1-M NaOH. The Cr-metal solution at each pH was pipetted into an Erlenmeyer flask containing lignin. Stirring was carried out using an incubator shaker at a speed of 250 rpm for the optimum contact time. After filtration, the solution was measured using UV-vis spectroscopy at a wavelength of 440 nm. The measurements were recorded and analyzed.
Results and Discussion
Isolation and carbonization of sugarcane bagasse lignin. Biomass lignin can be isolated from sugarcane waste biomass using the Björkman method (extraction), cellulolytic enzyme lignin method (enzymatic), and technical lignin isolation method (acid dissolution) [13].
Among these methods, the most effective is the technical lignin isolation method from the study by Saleh et.al., 2018. The obtained lignin was 3.051 g with a yield of 6.10%, almost consistent with the yields reported by Moubarik et al. in 2013 (6.2%) [14]. The carbonization or curing of bagasse lignin opens the pores in lignin and eliminates components other than carbon. This method of sugarcane bagasse lignin carbonization was adopted from the study by Gustan Pari et al. in 2006 [8]. Bagasse lignin (BL) was carbonized by heating lignin in the furnace at 500 °C for 1 h to produce bagasse lignin carbon (BLC);
500 °C was selected because lignin started to decompose at this temperature, resulting in a good charcoal structure.
Given that bagasse contains volatile components, water, carbon, and ash, high temperatures are not recommended for the carbonization of bagasse lignin [15].
Fourier transform infrared spectroscopic characterization. Based on the infrared absorption properties of the functional group, FTIR spectroscopy was conducted to evaluate the samples and determine their molecular structure. The presence of a hydroxyl alcohol group and a phenol hydroxyl group is characteristic of the monomer’s lignin. Figures 1 shows the FTIR characterization of bagasse lignin (BL).
FTIR spectrum analysis of BL showed the presence of several sharp peak, which are characteristic of BL compounds based on their constituent functional groups.
A broad valley was found at 3450 cm−1, indicating the stretching vibration of the O–H bond, a phenolic hydroxy group. Slightly sharp peak appeared at 2930, 1520, 1130, and 1050 cm−1, indicating the stretching vibration of the aliphatic C–H bond, aromatic C=C bond, C–O alcohol bond, and C–O ether bond, respectively.
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Figure 1. FTIR Spectra Isolation of Sugarcane Bagasse Lignin (BL)
Figure 2. FTIR Spectra of Sugarcane Bagasse Lignin (BL) and Standard Alkali Lignin
Lignin can be classified into four categories based on the isolation method: alkaline lignin/kraft lignin, lignosulfonate, organosolv lignin, and soda lignin. BL belongs to alkaline lignin/kraft lignin. Figure 2 shows a
comparison of the FTIR spectra between BL and commercial standard alkaline lignin, which demonstrates the same wavenumber absorption region for both lignins.
However, standard alkaline lignin had a sharper
absorption peak intensity than the isolated BL. The results showed that the isolated BL was classified as alkaline lignin because the isolation from bagasse biomass utilizes a solution of NaOH (good alkali) that forms a black liquid (black liquor).
FTIR characterization of BLC was carried out to determine the presence of functional groups resulting from the heating process at 500 °C for 1 h in the furnace.
Figure 3 shows a comparison of the FTIR spectra of BLC and BL. Differences were observed between BL and BLC, particularly at wave number 1114 cm−1 where a
slightly sharp valley was formed, indicating the symmetrical stretching vibrations of CH3 and CH2 bonds in BLC. In the absorption region, O–H phenol, aliphatic C–H, C–O alcohol, and C–O ether were no longer found in BLC. Heating at high temperatures caused the functional groups in bagasse lignin to evaporate, and only carbon functional groups remained. The absorption area of aromatic C=C in BLC was not found because carbonization rearranged the carbon atoms.
The difference occurred in five vibrations. Table 1 summarizes the analysis of the FTIR results.
Figure 3. FTIR Spectrum of Sugarcane Bagasse Lignin (BL) and Carbon Lignin (BLC)
Table 1. Results of FTIR Analysis of Sugarcane Bagasse Lignin (BL) and Aminated Lignin (LA)
Bonding Vibration Vibration Type Wave Number (cm−1)
Sugarcane Bagasse Lignin Carbon Lignin
O–H Phenol Stretch 3450 -
N-–H Amine Symmetry Stretch - -
C–H Aliphatic Stretch 2930 2940
C=C Aromatic Stretch 1520 -
C–N Amine Stretch - -
C–O Alcohol Stretch 1130 1150
C–O Ether Symmetry Stretch 1050 -
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Figure 4. SEM Morphology of Sugarcane Bagasse Lignin Surface (A), Sugarcane Bagasse Lignin Carbon (B), from Left-right (Zoom in 2000x)
Figure 5. Graph of the Relationship between Mass Variations of BL (ash), BLC (red), Adsorbents with 60-ppm Cr Ion Solution
Scanning electron microscope characterization. BL has an irregular granule-shaped structure with many voids as shown in the SEM results in Figure 4 A. This structure renders the surface open and not compact. The use of NaOH in BL isolation caused the microstructure of the bagasse to become coarse and stringy. [16]. The results are shown in Figure 4 B. The surface structure of BLC has coarse pores and uneven particle distribution.
Carbonization causes component evaporation, leaving some space and producing pores; as a result, the adsorbent exhibits a high surface area and increased adsorption capacity [17]. Carbonization roughened up the surface of lignin, thus increasing its surface area and adsorption capacity for heavy ion absorption. Figure 4 shows the SEM results.
Adsorption ability. The adsorption ability of BL and BLC for Cr ion solution was evaluated. Three variables, namely, adsorbent mass, contact time, and pH, were utilized to evaluate the adsorption ability. First, the mass of the two adsorbents was varied to determine their optimum mass for Cr ion adsorption. Figure 5 shows the correlation between the mass variation of bagasse carbon lignin and bagasse lignin as a Cr ion adsorbent.
On the basis of the experimental results for percent removal, the efficiency for the absorption of Cr metal ions is in the order BLC (red) > BL (ash). BLC exhibits higher absorption than BL. Carbonization opens the surface pores of lignin, thus increasing the surface area and promoting the absorption. The optimum mass for the
0,01 0,02 0,03 0,04 0,05 0,06 0,07 0,08
0 5 10 15 20 25 30
% Removal
Mass (gram)
Lignin Bagasse Furnance (LBF)
Lignin Bagasse (LB)
two types of lignin adsorbents (BL and BLC) was 0.015 g as indicated by the high percent removal. Further increasing the amount of adsorbent can increase the effect of aggregation (agglomeration) or the less-active sites that can be used. The optimum mass was used as a reference for testing other variations. Next, the contact time variation with the optimum mass was evaluated to
determine the optimal contact time between the two types of lignin adsorbents (BL and BLC) and Cr ion absorption.
The optimum contact time was selected from the highest percent removal rate. Figure 6 shows the results of the adsorption ability test using variations in contact time for the two types of lignin samples.
Figure 6. Graph of the Relationship of Contact Time Variations on BL (ash) and BLC (red) Adsorbents with 60-ppm Cr Ion Solution
Figure 7. Graph of the Relationship of Variations in pH to Adsorbents BL (ash), BLC (red), with 60 ppm Cr Ion Solution
The optimum contact time for the two types of lignin (BL and BLC) was 90 min. The longer the contact time, the greater the percent removal. According to the study published in 2011 by Isna Syauqiah et al. [18], the longer
the contact time, the longer the interaction between the adsorbate and adsorbent, resulting in increased adsorbent absorption or adsorption. For the three types of adsorbents, the percent removal continued to increase
15 30 45 60 75 90
0 5 10 15 20 25 30
% Removal
Contact Time (mins) Lignin Bagasse Furnance (LBF)
Lignin Bagasse (LB)
0 1 2 3 4 5 6 7 8 9
0 1 2 3 4 5 6 7 8
% Removal
pH
Lignin Bagasse Furnance (LBF)
Lignin Bagasse (LB)
Isolation of Lignin from Sugarcane Bagasse as an Adsorbent 223
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with the contact time from a predetermined duration of 90 min because the active sites in the three types of lignin (BL and BLC) have not reached saturation at 90 min.
In the pH variation test, the optimum adsorbent mass and contact duration achieved in the previous test were employed. This test was conducted to determine the optimum pH of the adsorbate or Cr ion solution because pH plays an essential role in the adsorption of heavy ions.
Figure 7 shows the results of the adsorption ability test for the two types of lignin samples under varying pH levels.
The absorption efficiency of heavy metal Cr ions was tested in the pH range of 1–8. The figure above shows that for the three types of adsorbents at pH 1–5, the percent removal continued to increase and the peak was completed at pH 6. Therefore, pH 6 was considered as the optimum pH for Cr ion adsorption. At neutral and alkaline pH levels, the percent removal value decreased again. This phenomenon occurred because at low pH, H3O+ ions with high concentrations compete with heavy ions such as Cr to occupy the active sites during adsorption [19]. In an acidic pH solution, the excess of protons causes a rejection between the surface of the adsorbent and heavy ions (adsorbate), so absorption or adsorption will decrease [20]. At neutral pH (pH 7), the absorption efficiency tends to decrease because the ions undergo hydrolysis, thereby making the situation unstable and reducing absorption. At alkaline pH, ions form metal hydroxide deposits, so absorption is hindered [21].
Adsorption kinetics. Adsorption kinetics is the adsorption rate of a fluid by the adsorbent in a certain period. The adsorption kinetics of a substance can be determined by measuring changes in the concentration of the adsorbed substance and analyzing the value of k (in the form of slope) and plotting it on a graph. The adsorption kinetics is influenced by the absorption reaction that occurs between the adsorbent and adsorbate and the transfer of ions to the active adsorption sites in the adsorbent. This study used two adsorption kinetics models, namely, the pseudo-first order kinetic model and the pseudo-second order kinetic model. The former
describes a reversible equilibrium between the liquid phase in the adsorbate and the solid phase in the adsorbent. The latter features a limiting adsorption rate by considering a chemical reaction that occurs, such as electrostatic interactions, complex formation, and chelation formation [22].
The type of adsorption kinetics model can be inferred from R2, which can be obtained from the linear straight- line equation plotted between log (Qe − Qt) against time (t) in the pseudo-first order kinetic model. Meanwhile, the pseudo-second order kinetic model can be obtained from the linear straight-line equation between t/Qt against time (t). From the two plots of the linear straight-line equation, the coefficient of determination R2 can be obtained. Table 2 summarizes the results of the adsorption kinetics test.
According to the adsorption kinetics model and the summary of R2 values above, the adsorption mechanism of Cr ions on the two types of lignin adsorbents (BL and BLC) followed the pseudo-first order adsorption kinetics model. Cr metal ions stick to the active site of the adsorbent and form an active complex compound [23].
The pseudo-first order adsorption kinetics model also explained that the reaction rate depends on one of the reacting substances.
Adsorption isotherm. The equation of the adsorption isotherm, which is a distribution process that occurs between a solid-phase adsorbent and a liquid-phase adsorbate, defines the adsorption process. The Freundlich adsorption isotherm and the Langmuir adsorption isotherm are the two most often utilized adsorption isotherms [24].
Table 3 lists several adsorption isotherm parameters.
Table 2. Summary of Adsorption Kinetics Test Results
BL BLC
Orde 1 R2 = 0,9345 R2 = 0,8664 Orde 2 R2 = 0,3301 R2 = 0,6533
Table 3. Parameter of Adsorption Isotherm of each Adsorbent Adsorbent Temperature
(°C)
Langmuir Freundlich
Qm (mg/g) KL (L/mg) R2 1/n KF R2
Lignin Bagasse
25 0,5509 289,31 0,8747 2,9232 1,67x10−5 0,9202
30 8,6050 2,25 0,8010 1,4359 1,49x10−2 0,9313
35 0,8181 144,39 0,7816 2,2922 1,74x10−4 0,9908
40 1,1507 68,34 0,8633 2,5766 1,04x10−4 0,9361
Lignin Bagasse Furnace
25 1,1922 60,76 0,8696 2,7160 7,53x10−5 0,9526
30 9,8717 1,48 0,9070 1,5178 1,55x10−2 0,9490
35 2,2242 19,77 0,9159 2,1633 7,00x10−4 0,9874
40 3,0921 10,11 0,9347 2,1616 1,00x10−3 0,9300
(a) (b)
Figure 8. Graph of Determination of Enthalpy and Entropy Values: (a) Lignin Bagasse and (b) Lignin Bagasse Carbon Table 4. Thermodynamic Parameters
Adsorbent Temperature (K) Thermodynamic Parameters
∆G° kJ/mol ∆H° kJ/mol ∆S° J/molK
Sugarcane Bagasse Lignin
298 −50,90
4,71 140,81
303 −39,52
308 −50,82
313 −49,70
Sugarcane Bagasse Lignin Carbon
298 −47,03
−78,16 2667,71
303 −38,46
308 −45,73
313 −44,73
Table 3 shows that the R2 value for the two types of adsorbents was close to 1, indicating the suitability of the Freundlich isotherm equation model. The Freundlich isotherm model of the adsorption of Cr ions on the two types of lignin adsorbents (BL and BLC) showed that adsorption occurs in multilayer and the surface is heterogeneous or each active group on the surface of the adsorbent has different binding energy [25]. In addition, the adsorbate can move freely so that adsorption takes place in many adsorption layers [26].
Adsorption thermodynamics. Thermodynamic parameters such as free energy change (Gº) and enthalpy change (Hº) and entropy change (Sº) were calculated to fully understand the nature of adsorption.
These thermodynamic parameters for the adsorption can be estimated by considering the equilibrium constants under several experimental conditions using the following equations [27, 28]:
Gibbs energy change ΔG° was calculated as follows:
∆G0 = −RT ln K (1)
A negative-Gibbs free energy value indicates the feasibility and spontaneous nature of the adsorption (27).
Distribution constant K can be expressed as (28):
K = Cad / Ce, (2) where Cad (mg/l) and Ce (mg/l) denote the concentration of solute adsorbed at equilibrium and the solute concentration in solution at equilibrium, respectively. R is the gas constant with a value of 8.314 Jmol−1 K−1, and T is the absolute temperature in Kelvin (K). The relationship of (ΔG°) to enthalpy change (ΔH°) and entropy change (ΔS°) of adsorption was expressed as:
ΔG0 = ΔH0 − TΔS0 (3) Substituting Equation 1 into Equation 3 yielded
ln K = −(ΔH0/RT) + (∆S0)/R (4) The values of ΔH° and ΔS° were determined from the slope and intercept of the linear plot of (ln K) versus (1/T) of Equation 4 (Figure 8).
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Makara J. Sci. September 2023 Vol. 27 No. 3
A positive value of change in enthalpy (ΔH°) indicates that the adsorption is endothermic, and a positive value of change in entropy (ΔS°) reflects the increased randomness at the solid/solution interface. From the graph of the linear curve, the equation of a straight line was obtained to determine the value of enthalpy (∆H°) and entropy (∆S°).
As shown in Table 4, the thermodynamics of Cr ion adsorption by the two types of lignin adsorbents (BL and BLC) exhibited negative Gibbs free energy (∆G°). This finding indicated that the reaction between the Cr ion and the lignin adsorbent occurred spontaneously. Meanwhile, the enthalpy value (∆H°) for the adsorbents BL and BLC was positive.
On the basis of their enthalpy values (below 40 kJ/mol), BL and BLC underwent endothermic adsorption by physisorption [28]. The entropy value (∆S°) for BL was positive, indicating the increased level of disorder in the solid liquid adsorption system between the adsorbent and adsorbate. The increase in the entropy value can be attributed to the number of water molecules transferred;
most of the entropy was translated rather than lost by Cr ions, resulting in increased randomness at the solid/solution interface [29]. The positive entropy value (∆S°) also indicated that the adsorption process is driven by entropy rather than enthalpy [28]. Meanwhile, BLC exhibited a negative entropy value, indicating that irregularities occurred during adsorption of Cr ions by BLC. As a result, the freedom, or the system became orderly.
Conclusions
Lignin was successfully isolated from bagasse with a yield of 6.102%. FTIR analysis showed that BL belongs to the type of synapcyl alcohol lignin. BLC only had symmetric stretching vibrations of CH3 and CH2 bonds (1114 cm−1), indicating that carbonization was successful. SEM characterization for both samples showed their rough and irregular surface morphology.
The ability of lignin adsorbents (BL and BLC) to adsorb Cr ions resulted in optimum conditions at an adsorbent mass of 0.015 g, a contact time of 90 min, and adsorbate- solution pH of 6. The adsorption capacity (Qm) of BL adsorbent was 8.6050 mg/g at 30 °C, and that of BLC was 9.8717 mg/g at 30 °C. The Cr ion adsorption followed the Freundlich isotherm model, showing that the adsorption occurs in multilayers. In addition, the surface is heterogeneous, or each active group on the adsorbent surface has a different binding energy. The Cr ion adsorption kinetics model followed the pseudo-first order kinetics. These findings suggested that Cr ions adhere to the adsorbent’s active site, forming an active complex molecule. The thermodynamics of Cr ion adsorption for BL revealed a spontaneous reaction at high temperatures.
Meanwhile, BLC exhibited a spontaneous reaction at low temperatures.
Acknowledgments and Grant
Thank you to PERTAMINA University for providing a laboratory for experiments.
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