Next Article in Journal
A Study of the Structure and Physicochemical Properties of the Mixed Basicity Iron Ore Sinter
Previous Article in Journal
Comparative Study of Magnetic Properties of (Mn1−xAxIV)Bi2Te4 AIV = Ge, Pb, Sn
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:

Surface Modifications of Superparamagnetic Iron Oxide Nanoparticles with Polyvinyl Alcohol and Activated Charcoal as Methylene Blue Adsorbents

Department of Chemical Engineering, International University—Vietnam National University, Ho Chi Minh City 70000, Vietnam
School of Chemical and Environmental Engineering, International University—Vietnam National University, Ho Chi Minh City 70000, Vietnam
Nanomaterials Engineering Research & Development (NERD) Laboratory, International University—Vietnam National University, Ho Chi Minh City 70000, Vietnam
Magnetochemistry 2023, 9(9), 211;
Submission received: 4 August 2023 / Revised: 7 September 2023 / Accepted: 18 September 2023 / Published: 20 September 2023
(This article belongs to the Section Applications of Magnetism and Magnetic Materials)


As novel methylene blue adsorbents, polyvinyl alcohol and activated charcoal were used to modify the surface of superparamagnetic iron oxide nanoparticles. The adsorption capacity after 69 h was 26.50 ± 0.99–40.21 ± 1.30 mg/g, depending on the temperature (333.15, 310.15, and 298.15 K) and the initial concentration of methylene blue, which was between 0.017 and 0.020 mg/mL. Based on thermodynamics parameters, the adsorption process can be considered to be spontaneous endothermic physisorption. Kinetics studies show that the pseudo-second-order model was the best-fitted model. Adsorption isotherm studies show that the best-fitted models were the Langmuir, Langmuir, and Temkin and Pyzhev isotherm models when adsorbing MB at 333.15, 310.15, and 298.15 K, respectively.

Graphical Abstract

1. Introduction

Although magnetic nanoparticles have various applications [1], water treatment is one of the most common applications [2,3,4,5]. The magnetic property makes the separation processes easier, especially in solid–liquid phases [6], leading to their application in water treatment. Hence, magnetic separation processes are receiving more attention from researchers globally. Magnetic properties can be obtained from various magnetic nanoparticles (i.e., iron oxide nanoparticles—IONPs). IONPs have different types, including magnetite, superparamagnetic iron oxide nanoparticles, and Fe3O4 (SPION). SPION, a hydrophobic material, can be synthesized via multiple methods, of which co-precipitation is the most rapid, with the highest yield of magnetite and a facile synthesis method due to the suppression of maghemite, despite several disadvantages such as agglomeration [1,7,8,9]. This might be caused by kinetic factors while crystals are growing during the nucleation and oxidation processes [1,7,8,9].
In water treatment, the presence of SPION can ease the separation process when removing synthetic dyes from water due to their magnetic properties [6]. While SPION nanoparticles have a large surface area, the adsorption capacity of synthetic dyes (i.e., methyl orange, Congo red, and methylene blue—MB) can be enhanced significantly when carbon-based materials are introduced (i.e., activated charcoal (AC), graphene oxide, and carbon nanotubes) due to their larger surface area, chemical structure (i.e., porosity), and superior adsorption capabilities [2,10,11,12,13,14,15,16,17,18,19,20]. For instance, the adsorption capacity of SPION is only 45.43 mg/g, while SPION/MWCNT, SPION@Carbon sheets, SPION/graphene oxide, and SPION/expanded graphite have adsorption capacities of 48.06, 95, 280.26, and 76.2 mg/g, respectively [21,22,23,24,25]. Recently, as an MB adsorbent, SPION has been modified using PVA and graphite, yielding SPION/PVA/GR [26]. However, one of the more inexpensive carbon-based materials is activated charcoal (AC). Commercial AC, one of the most used adsorbents due to its high pore value, huge surface area, high surface reactivity, and suitable pore distribution caused by the carbonization activation processes, can be produced from multiple sources of agricultural waste [27,28,29]. Hence, to improve the adsorption process of MB, which is a carcinogenic and toxic synthetic textile dye associated with cancer, skin disease, and mutations, modifying SPION with activated charcoal is necessary [30,31,32]. Removing methylene blue from wastewater is necessary to protect the environment and human health [32].
Even though the phase separation process between solid and liquid can be easy when using magnetic activated charcoal as an MB adsorbent, to enhance the rate of degradation of the pollutants and alter the physical form of the adsorbents (i.e., to a membrane or thin film), polymers such as polyvinylpyrrolidone, polyacrylonitrile, or especially polyvinyl alcohol (PVA) can be introduced into the composite [33,34,35,36,37,38]. Polymers can also affect the adsorption capacity of SPION-based MB adsorbents. For instance, SPION/chitosan/graphene oxide and SPION/PVA/chitosan/graphene oxide can have adsorption capacities of 30.01 and 36.4 mg/g, respectively [39,40].
This present study focuses on evaluating the potential of adsorbing MB onto SPION/PVA/AC materials, which can be synthesized via simple, environmentally friendly, and inexpensive methods. Moreover, using SPION/PVA/AC, there is a potential to make a magnetic thin film composite adsorb MB. Additionally, this work chose a very low initial concentration of MB to test the possibility of removing MB from diluted MB wastewater at 298.15–333.15 K. In this study, the characterization of SPION/PVA/AC and the quantitative method for adsorption experiments were adapted without any modifications similar to previous literature [26,40]. However, the surface charge of SPION was determined using zeta potential measurements. Additionally, by adapting the same methods and calculations without any modifications, as in previous publications, the adsorption kinetics (pseudo-first and pseudo-second-order, simplified Elovich), adsorption isotherm (Langmuir, Dubinin–Raduskevich, Halsey, Tempkin and Pyzhev, and Halsey), and thermodynamic properties were evaluated [26,40].

2. Material and Methods

2.1. Materials

From Xilong Scientific Co., Ltd. (Shantou, China), activated charcoal (AC) was bought. The remaining chemicals were used without any purification after being purchased from the same batch and companies as in the previous publication [26].

2.2. Synthesis

Solution A1—SPION synthesis: The synthesis process was adapted without any modifications from the previous publication [26].
Solution A2—SPION solution: Without any modifications, the SPION solution was prepared as in the previous publication [26].
Solution B—PVA solution: Without any modifications, the PVA solution was prepared as in the previous publication [26].
Solution C—AC solution: In 250 mL of deionized water, 12 g of dried AC was mixed for 1 h using sonication.
Solution D—SPION/PVA synthesis: Without any modifications, the SPION/PVA solution was prepared as in the previous publication [26].
Solution E—SPION/PVA/AC synthesis: To synthesize SPION/PVA/AC, solution C was initially mixed with solution D for 1 h. Then, the product was dried at 80 °C for 24 h.
Solution G—Methylene blue stock solution: Without any modifications, the MB solution was prepared as in the previous publication [26].
Solution H—Methylene blue diluted solution: Without any modifications, this step was adapted from the previous literature [26].

2.3. Adsorption/Loading Experiment

The adsorption/loading experiment was adapted from previous literature [26], except the aliquot was analyzed after every 25, 48, and 69 h. The adsorption experimental data were used to determine the loading/adsorption amount at equilibrium ( Q e , mg MB (g particles)−1), the loading/adsorption capacity (%LC), the entrapment efficiency (%EE), adsorption kinetics (pseudo-first-order linear/nonlinear, pseudo-second-order linear/nonlinear, simplified Elovich), adsorption isotherm (Langmuir, Tempkin and Pyzhev, Freundlich, Halsey, and Dubinin–Raduskevich), and thermodynamics properties using equations published in the previous literature [26,40,41].

3. Results and Discussion

3.1. Characterization of Adsorbent

Adapting from previous publications, after synthesizing SPION/PVA/AC, the FE-SEM, FTIR, XRD, BET, BJH, and VSM were used to characterize the adsorbents [26,40]. Additionally, the zeta potential can determine the type of surface charge of SPION.

3.1.1. FE-SEM

As shown in Figure 1a, adapting from previous publications [26,40], the morphology of IONPs (iron oxide nanoparticles) was evaluated. The IONPs seem to be aggregated, which is similar to previous publications [1,26,40].
Using ImageJ software v.1.53t, as shown in Figure 1b, IONPs have the mean particle size of 23.3 ± 2.4 nm. The average IONPs size matched the results of previous publications [1,26].
As shown in Figure 2a, using FE-SEM, the adsorbents, which are IONPs/PVA/AC (3:4:12 w/w/w), were characterized.
As shown in Figure 2a, while IONPs seem to be invisible, at the 5 μm scale, AC was clearly visible. However, as the magnification increased, in Figure 2b,c, the IONPs, which are on the surface of AC, were clearly visible. With some findings, in the area that was heavily concentrated with IONPs at 500 nm, as shown in Figure 2c, the IONPs were aggregated. This phenomenon can be explained by PVA coating the outer surface of IONPs, as demonstrated in Figure 2d. However, the aggregation can also be caused by the infamous disadvantage of the synthesis method (co-precipitation). Hence, XRD and FTIR were used to confirm Figure 2d.

3.1.2. XRD Analysis

To confirm whether IONPs were SPION, XRD analysis was performed [26]. As shown in Figure 3a, the peaks at 2θ positions of 18.28°, 30.17°, 35.51°, 43.17°, 53.65°, 57.16°, and 62.75° confirm that IONPs are magnetite—SPION [42]. Moreover, the hkl indices that correspond to these 2θ positions are (220), (311), (400), (422), (511), and (440), which is similar to the literature [43,44,45].
Based on Figure 3a, using the Scherrer equation at a reflective peak 2θ of 35.51° [46], the shape factor of 0.89, and the SPION size were determined to be 23.2 nm. This result corresponds to the FE-SEM analysis. As shown in Figure 3b, the peaks of SPION/PVA/AC have all the characteristic 2θ positions of SPION combining with the high-intensity peaks of AC and PVA, which indicated that SPION/PVA/AC was successfully constructed similar to Figure 2d.

3.1.3. FTIR

To determine types of bonds exists in the adsorbent, FTIR was used. The FTIR spectra were analyzed using the same instrument as the previous publication [26,40]. As seen in Figure 4, IONP were confirmed to be SPIONs due to the distinctive peaks at 584 and 446 cm−1 [26,40,47]. Additionally, as shown in Figure 4a, the wavelengths of 3419 and 1627 cm−1 also appear. These peaks were similar to previous publications [1,26,40,48,49,50].
Additionally, as shown in Figure 3 and Figure 4a, combining with the synthesis method similar to the literature, the IONPs that were used in this research can be considered as SPION [51,52,53,54]. As shown in Figure 4a, the PVA has peaks at 851, 1097, 1378, 1443, 1653, 1737, 2941, and 3418 cm−1, which correspond to the C-C stretching vibration, C=O stretching, C-H dormation vibration, CH2 bending, C=O carbonyl stretch, C=O stretching vibrational band, CH2 asymmetric stretching vibration, and O-H stretching vibration, respectively [26,55,56,57,58]. As shown in Figure 4a, the AC has peaks at 1634, and 3427 cm−1, which correspond to the C=O stretching vibration and the O-H stretching vibration [59]. In Figure 4a, SPION/PVA/AC has peaks at 3421, 2921, 1617, 1058, 677, 598, and 442 cm−1. These peaks were similar to the peaks of SPION, PVA, and AC. Hence, Figure 2d can be considered to be the morphology of SPION/PVA/AC.

3.1.4. Zeta Potential

To evaluate one of the nanoparticles’ physical properties, the zeta potential can be considered. By providing the electrical state of charged interfaces between dispersed particles, the electrostatic interaction can be measured using zeta potential [60]. The average zeta potential of SPION was 18.67 ± 6.16 mV at pH = 4–5, which was similar to other publications [61,62,63,64,65,66], and the nanoparticles were not stable in the colloid suspension [67]. However, the relationship between the zeta potential and the colloidal stability of nanoparticles in dispersion is conflicting in the literature [60]. However, based on the zeta potential reported above, the net charge of SPION nanoparticles was positive.

3.1.5. BJH Analysis

The adsorption–desorption isotherm in Figure 4b shows that starting at 0.1 p/po, the volume of the adsorbate uptake increases to a higher p/po.
From Figure 4b, a type IV isotherm can be seen. This can be interpreted that the adsorbent has a small amount of micropores (with a size between 2 and 50 nm) in its mesoporous structure [68,69]. Additionally, the hysteresis loop can be considered H3 type, indicating that the adsorbents have a wide pore size distribution [41]. As shown in Table 1, the SPION/PVA/AC’s average pore diameter was shown.
In addition to determining the surface area of 751 m2/g, Table 1 also determines the total pore volume of the adsorbent to be 0.38 cm3/g and the average pore diameter of the SPION/PVA/AC to be 10 Å.

3.1.6. VSM Analysis

As shown in Figure 4c, consistent with the literature, the saturation magnetization (Ms) was found to be 69.7 emu/g. This value was similar to the literature, indicating that IONPs have superparamagnetic properties [26,51,70,71,72,73,74].
Based on the shape of the hysteresis loop in Figure 4c, the SPION/PVA/AC can be concluded to have superparamagnetic properties as well, even though the magnetization magnitude decreases significantly compared to bare SPION from 69.7 to 10.5 emu/g. This phenomenon can be explained similar to the FE-SEM results for PVA-coated SPION [75]. From the FE-SEM, FTIR, and VSM analyses, as shown in Figure 2d, the structure of the adsorbent was proposed.

3.2. Loading Capacity of SPION/PVA/AC and Modelling

Using the same settings and instruments of UV-Vis spectrometry as in the literature, the MB concentration was quantified [26,40]. As shown in Table 2, the measured MB concentration, Qt, %LC, and %EE of the adsorption process at 273.15, 303.15, and 333.15 K can be calculated.
From Table 2, comparing to Table 1, SPION/PVA/AC has an adsorption capacity 3% higher than SPION/PVA/CS/GO [40] and SPION/CS/GO [39]. However, SPION/PVA/AC has slightly lower adsorption capacities than SPION (17.5%) [21], SPION/MWCNT (22%) [22], and SPION@Graphene (17.2%) [76]. Despite these small changes in adsorption capacity, SPION/PVA/AC consists of cheaper materials compared to SPION/CS/GO, SPION/MWCNT, and SPION@Graphene. Hence, the benefits of low cost can outweigh the slight decreases in the adsorption capacities. When compared to SPION, despite its more expensive and smaller adsorption capacities, SPION/PVA/AC consists of PVA, which can further modify the physical form of the adsorbents (i.e., thin film). Additionally, after 24 h, at 333.15 K, in four different concentrations, at least 85% methylene blue was adsorbed, while only 55% methylene blue was adsorbed at 298.15 K. This shows that as the temperature increases, the loading amount, loading capacity, and entrapment efficiency increase significantly after 24 h. Hence, temperature has significant effects on adsorption capacity.
Due to the effect of temperature, the thermodynamic parameters were calculated and are given in Table 3.
As shown in Table 3, a feasible and spontaneous adsorption process can be interpreted by G < 0 [77,78,79,80,81]. To further interpret the G value, as the temperature increases, G becomes more negative. This indicates that physical forces are the main factor in the adsorption process, and adsorption is more favorable at higher temperatures [77,82]. In addition, the value of S , which is greater than zero, indicates that during the adsorption process, the surface randomness increases and the MB and SPION/PVA/AC internal structures change [77,78,79,80,81]. Additionally, H > 0 indicates that the adsorption process was endothermic, there was an occurrence of monolayer adsorption, and weak chemical forces between the adsorbents and MB exist [77,78,79,80,81]. The endothermic adsorption process means that the adsorption degree increases as the temperature increases [80]. The endothermic adsorption can be explained by the interaction between pre-adsorbed water and SPION/PVA/AC, which is stronger than the interaction between MB and SPION/PVA/AC [83]. Hence, MB molecules have to compete for the active sites of SPION/PVA/AC against water molecules, resulting in the simultaneous adsorption–desorption of MB and water, yielding H > 0 [84,85]. The adsorption process can be considered to be physisorption if the H > 40 kJ/mol [77,80]. As shown in Table 3, as the indicator, the H < 20 kJ/mol shows that Van der Waals forces dominate the physisorption interaction [86]. Additionally, this value also indicates that the electrostatic interactions and forces of attraction were weak and the bonding between MB and the adsorbents was loose [87,88,89]. After determining the relationship between temperature and adsorption capacities, the relationship between time and adsorption capacities were investigated (as shown in Table 4).
As shown in Table 4, the adsorption capacity increased as the temperature increases from 298.15 to 310.15 K, indicating an endothermic process, which is in accord with H > 0 [77,78]. However, the adsorption capacity decreased insignificantly as the temperature reached 333.15 K. This phenomenon might be due to the decrease in adsorption forces between the active sites of SPION/PVA/AC and MB [90,91] and the increase in mobility of MB ions [92]. When increasing the initial MB concentration, the driving force of mass transfer is higher, leading to an increase in adsorption/loading capacity [93]. After 25 h, at a temperature of 333.15 K, the loading capacity did not deviate much. This phenomenon can be caused by a decreased ratio between the free methylene blue molecules and the abundant free adsorption sites available [92,94]. From Table 4, to have the highest adsorption capacities, SPION/PVA/AC must be in contact with MB solution at the concentration of 0.02 mg/mL for 69 h at 310.15 K. After adsorbing almost all the methylene blue (%EE was close to 100%), values of loading amount (Qt) and time (t) were used to calculate the adsorption kinetics using multiple kinetics models.
As shown in Table 5 and Figure 5, at different adsorption conditions (i.e., temperature, time, and MB concentration), the pseudo-second-order and simplified Elovich kinetic model can determine the adsorption rate and the loading amount at equilibrium.
As shown in Table 5, at 333.15, 310.15, and 273.15 K, out of all the mentioned kinetics models, the pseudo-second order can be considered to be the most fitted for SPION/PVA/AC due to the small χ2 and R2 values. The pseudo-second-order kinetic model, which is shown in Table 5, indicates that the adsorption mechanism is involved in chemisorption via electrons transferring (valence forces) between MB and the adsorbent [95,96,97,98,99].
As the temperature increased from 273.15 to 310.15 K, the k2 values increased as well, indicating a faster adsorption rate at high temperatures [92]. Moreover, depending on the adsorption conditions (i.e., adsorption contact time and adsorption amount), the MB adsorption rate decreases as time increases. This phenomenon can be caused by the conversion of MB to the MB+ cationic form [77].
After 25 h, MB had a slight shift in the UV-VIS peak wavelength when the adsorption experiments were at T = 333.15 K. However, at 298.15 K and 310.15 K, the phenomenon was not seen. The wavelength shift phenomenon can be seen and explained similarly to previous publications [26].
Comparing the obtained experimental and calculated equilibrium adsorption capacities (as shown in Table 4 and Table 5), these values were much smaller compared to some literature [100,101,102,103,104,105,106,107,108] and much greater compared to other literature [89,93,109,110,111,112]. Similar to the previous publication, as shown in Table 6, various adsorption isotherm models, including isotherm constants, were determined [26].
The adsorption experimental parameters can be fitted using all the above isotherm models, based on the R2 values, except Langmuir at 298.15 K. However, as shown in Table 6, at 310.15 and 333.15 K, the best-fitted isotherm model is Langmuir due to the highest R2 values. Similarly, at 298.15 K, the best-fitted isotherm model is Temkin and Pyzhev due to the highest R2 value. As shown in Table 6, at 310.15 and 333.15 K, since 0 < average RL < 1 in the Langmuir adsorption isotherm models (as shown in Figure 6), the adsorption mechanism can be described as the attachment of MB onto the surface of SPION/PVA/AC, which is favorable [2,22]. From the Langmuir isotherm model, the adsorbent’s surface can be considered to be homogeneous, and MB was adsorbed as a monolayer [25,26].
As shown in Figure 7, from the Frendlich isotherm model, at 333.15 K, the 1 n F value indicates the non-favorable physical process [26].
At 310.15 K, as 1 n F is the closest to 0, the physical process was favorable. Moreover, the values of nF, which were smaller than 1 at T = 333.15 K and 298.15 K, represent the poor adsorption characteristic, while at 310.15 K, the nF value was greater than 1, which indicates the good adsorption characteristic [77]. Since 1 n F > 1 , the adsorption process has involved cooperative adsorption [26,102,113]. Moreover, since nF < 1, with surface density, the bond energies increase [26,114].
Looking at the Dubinin–Radushkevich model, as shown in Figure 8, the R2 value was greater than 0.5, which indicates that the adsorption between SPION/PVA/AC and methylene blue occurred in relevance with this isotherm at all temperatures [115].
Since KDR < 1, the surface heterogeneity increased due to the pore structure of SPION/PVA/AC and the interactions between SPION/PVA/AC and MB [26,116]. Because E < 0, the sorption process is exothermic [117]. When E is between 8 and 16 kJ/mol or E < 8 kJ/mol, the adsorption process that occurs can be chemical ion-exchange or physical adsorption, respectively [26,118,119,120,121]. Hence, from Figure 8, the sorption process can be considered to be physical adsorption.
On the other hand, at 298.15 K, the best-fitted adsorption isotherm model was Temkin and Pyzhev, as shown in Figure 9, with an R2 value of 0.999.
The Temkin and Pyzhev model shows that adsorption is characterized by a uniform distribution of binding energies, up to some maximum binding energy [122,123]
Similar to the Freundlich isotherm model, the Halsey isotherm model can examine an adsorption system that has multilayered and heterogeneous surfaces with a uniform surface heat distribution [26,124]. Hence, at 273.15 K, 310.15 K, and 333.15 K, the only model that is not the worst-fitted model is Halsey, as shown in Figure 10, and it has similar R2 values as the Freundlich isotherm model.
As shown in Table 6, at 333.15 K, since I 0 , the intraparticle diffusion model can be considered to be not only intraparticle diffusion but also film diffusion [26,77].
Additionally, from the data in Table 7 and Figure 11, as the kI values decrease while temperature increases, combining with the I values, the diffusion process (intraparticle and film) happened simultaneously [125,126,127].
In addition to intraparticle diffusion, film diffusion, chemisorption, and physical adsorption, other adsorption mechanisms could include the electrostatic interaction of surface negative charge with the positively charged methylene blue, the hydrogen bonding, and the π-π* stacking with the aromatic ring of methylene blue [125,126,127]. Moreover, the adsorption mechanisms can be controlled by external diffusion and boundary layer diffusion [77,88,128]. Hence, the adsorption was not only controlled by the rate-control step but also by some of the kinetic models and intraparticle diffusion as well.

4. Conclusions

Using polyvinyl alcohol and activated charcoal to modify the surface of superparamagnetic iron oxide nanoparticles, the materials can adsorb MB at 333.15, 310.15, and 298.15 K with the adsorption capacity after 69 h ranging from 26.50 ± 0.99 to 40.21 ± 1.30 depending on the temperature and the initial concentration of methylene blue, which were between 0.017 and 0.020 mg/mL. The thermodynamic parameters indicate that the adsorption was endothermic, spontaneous, and physisorption. The adsorption capacity increased as temperature increased despite the physical change of methylene blue at 333.15 K based on the shift in the UV-VIS peak wavelength. Based on the adsorption kinetics (pseudo-second order) and the intraparticle diffusion model, the adsorption mechanism can be considered chemisorption and exothermic. The Langmuir, Langmuir, and Temkin–Pyzhev isotherm models were the best-fitted models at 333.15, 310.15, and 298.15 K, respectively.


This research is funded by International University. VNU-HCM under grant number T2022-01-CEE.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

All data that support the findings of this study are included within the article.


The following undergraduate students from International University—Vietnam National University, Ho Chi Minh City, Vietnam are greatly acknowledged: Ngan T.N. Nguyen, Linh Bui, Tan Nguyen, and Tu Nguyen. The contribution of Mai V.T. Tam who affiliates to the Institute for Computational Science and Technology, Ho Chi Minh City was greatly recognized.

Conflicts of Interest

The author declare no conflict of interest.


C0initial concentration
C t concentration at time t
Vreaction volume
mmass of the nanoparticles
h 0 initial adsorption rate
Q e the amounts of MB (an adsorbate) adsorbed at the equilibrium
Q t ,the amounts of MB adsorbed at time t
k 1 the pseudo-first-order rate constant
k 2 pseudo-second-order rate constant
C e the equilibrium aqueous-phase concentration adsorbate
Q 0 the monolayer adsorption capacity which can be understood as the theoretical adsorption capacity
K L the constant related to the free adsorption energy and the reciprocal of the concentration at which half saturation of the adsorbent is reached
Q m the quantity of adsorbate adsorbed in a single monolayer
θ the fractional surface coverage
k a the respective rate constant for adsorption
k d the respective rate constant for desorption
1 n F the intensity of the adsorption
K F constant of the relative adsorption capacity of the adsorbent
Q m D R theoretical saturation capacity
K D R the activity coefficient related to mean free energy of adsorption
ε the Polanyi potential
Runiversal gas constant
K T P equilibrium binding constant
B1related to the heat of adsorption
K H a the Halsey isotherm constant
k i intraparticle diffusion rate constant
α the theoretical initial adsorption rate
β the theoretical desorption constant
G Gibbs free energy change
H standard enthalpy change
S entropy change
K0thermodynamic equilibrium constant in the adsorption process


  1. Doan, L.; Lu, Y.; Karatela, M.; Phan, V.; Jeffryes, C.; Benson, T.; Wujcik, E.K. Surface Modifications of Superparamagnetic Iron Oxide Nanoparticles with Polylactic Acid-Polyethylene Glycol Diblock Copolymer and Graphene Oxide for a Protein Delivery Vehicle. Eng. Sci. 2019, 7, 10–16. [Google Scholar] [CrossRef]
  2. Bayazit, Ş.S. Magnetic Multi-Wall Carbon Nanotubes for Methyl Orange Removal from Aqueous Solutions: Equilibrium, Kinetic and Thermodynamic Studies. Sep. Sci. Technol. 2014, 49, 1389–1400. [Google Scholar] [CrossRef]
  3. Ge, M.; Xi, Z.; Zhu, C.; Liang, G.; Hu, G.; Jamal, L.; S. M., J.A. Preparation and Characterization of Magadiite–Magnetite Nanocomposite with Its Sorption Performance Analyses on Removal of Methylene Blue from Aqueous Solutions. Polymers 2019, 11, 607. [Google Scholar] [CrossRef]
  4. Nicola, R.; Costişor, O.; Muntean, S.-G.; Nistor, M.-A.; Putz, A.-M.; Ianăşi, C.; Lazău, R.; Almásy, L.; Săcărescu, L. Mesoporous Magnetic Nanocomposites: A Promising Adsorbent for the Removal of Dyes from Aqueous Solutions. J. Porous Mater. 2020, 27, 413–428. [Google Scholar] [CrossRef]
  5. Nicola, R.; Muntean, S.-G.; Nistor, M.-A.; Putz, A.-M.; Almásy, L.; Săcărescu, L. Highly Efficient and Fast Removal of Colored Pollutants from Single and Binary Systems, Using Magnetic Mesoporous Silica. Chemosphere 2020, 261, 127737. [Google Scholar] [CrossRef]
  6. Altıntıg, E.; Altundag, H.; Tuzen, M.; Sarı, A. Effective Removal of Methylene Blue from Aqueous Solutions Using Magnetic Loaded Activated Carbon as Novel Adsorbent. Chem. Eng. Res. Des. 2017, 122, 151–163. [Google Scholar] [CrossRef]
  7. Kim, D.K.; Zhang, Y.; Voit, W.; Rao, K.V.; Muhammed, M. Synthesis and Characterization of Surfactant-Coated Superparamagnetic Monodispersed Iron Oxide Nanoparticles. J. Magn. Magn. Mater. 2001, 225, 30–36. [Google Scholar] [CrossRef]
  8. Marinin, A. Synthesis and Characterization of Superparamagnetic Iron Oxide Nanoparticles Coated with Silica. Master’s Thesis, Royal Institute of Technology, Stockholm, Sweden, 2012. [Google Scholar]
  9. Muthiah, M.; Park, I.-K.; Cho, C.-S. Surface Modification of Iron Oxide Nanoparticles by Biocompatible Polymers for Tissue Imaging and Targeting. Biotechnol. Adv. 2013, 31, 1224–1236. [Google Scholar] [CrossRef] [PubMed]
  10. Xu, P.; Zeng, G.M.; Huang, D.L.; Feng, C.L.; Hu, S.; Zhao, M.H.; Lai, C.; Wei, Z.; Huang, C.; Xie, G.X.; et al. Use of Iron Oxide Nanomaterials in Wastewater Treatment: A Review. Sci. Total Environ. 2012, 424, 1–10. [Google Scholar] [CrossRef]
  11. Duan, J.; Liu, R.; Chen, T.; Zhang, B.; Liu, J. Halloysite Nanotube-Fe3O4 Composite for Removal of Methyl Violet from Aqueous Solutions. Desalination 2012, 293, 46–52. [Google Scholar] [CrossRef]
  12. Zhu, H.-Y.; Fu, Y.-Q.; Jiang, R.; Jiang, J.-H.; Xiao, L.; Zeng, G.-M.; Zhao, S.-L.; Wang, Y. Adsorption Removal of Congo Red onto Magnetic Cellulose/Fe3O4/Activated Carbon Composite: Equilibrium, Kinetic and Thermodynamic Studies. Chem. Eng. J. 2011, 173, 494–502. [Google Scholar] [CrossRef]
  13. Yang, N.; Zhu, S.; Zhang, D.; Xu, S. Synthesis and Properties of Magnetic Fe3O4-Activated Carbon Nanocomposite Particles for Dye Removal. Mater. Lett. 2008, 62, 645–647. [Google Scholar] [CrossRef]
  14. Wang, J.; Tang, B.; Tsuzuki, T.; Liu, Q.; Hou, X.; Sun, L. Synthesis, Characterization and Adsorption Properties of Superparamagnetic Polystyrene/Fe3O4/Graphene Oxide. Chem. Eng. J. 2012, 204–206, 258–263. [Google Scholar] [CrossRef]
  15. Ren, X.; Chen, C.; Nagatsu, M.; Wang, X. Carbon Nanotubes as Adsorbents in Environmental Pollution Management: A Review. Chem. Eng. J. 2011, 170, 395–410. [Google Scholar] [CrossRef]
  16. Gong, J.-L.; Wang, B.; Zeng, G.-M.; Yang, C.-P.; Niu, C.-G.; Niu, Q.-Y.; Zhou, W.-J.; Liang, Y. Removal of Cationic Dyes from Aqueous Solution Using Magnetic Multi-Wall Carbon Nanotube Nanocomposite as Adsorbent. J. Hazard. Mater. 2009, 164, 1517–1522. [Google Scholar] [CrossRef]
  17. Deligeer, W.; Gao, Y.W.; Asuha, S. Adsorption of Methyl Orange on Mesoporous γ-Fe2O3/SiO2 Nanocomposites. Appl. Surf. Sci. 2011, 257, 3524–3528. [Google Scholar] [CrossRef]
  18. Leodopoulos, C.; Doulia, D.; Gimouhopoulos, K.; Triantis, T.M. Single and Simultaneous Adsorption of Methyl Orange and Humic Acid onto Bentonite. Appl. Clay Sci. 2012, 70, 84–90. [Google Scholar] [CrossRef]
  19. Amin, N.K. Removal of Direct Blue-106 Dye from Aqueous Solution Using New Activated Carbons Developed from Pomegranate Peel: Adsorption Equilibrium and Kinetics. J. Hazard. Mater. 2009, 165, 52–62. [Google Scholar] [CrossRef]
  20. Ghaedi, M.; Taghavimoghadam, N.; Naderi, S.; Sahraei, R.; Daneshfar, A. Comparison of Removal of Bromothymol Blue from Aqueous Solution by Multiwalled Carbon Nanotube and Zn(OH)2 Nanoparticles Loaded on Activated Carbon: A Thermodynamic Study. J. Ind. Eng. Chem. 2013, 19, 1493–1500. [Google Scholar] [CrossRef]
  21. Li, Z.; Sun, Y.; Xing, J.; Meng, A. Fast Removal of Methylene Blue by Fe3O4 Magnetic Nanoparticles and Their Cycling Property. J. Nanosci. Nanotechnol. 2019, 19, 2116–2123. [Google Scholar] [CrossRef]
  22. Ai, L.; Zhang, C.; Liao, F.; Wang, Y.; Li, M.; Meng, L.; Jiang, J. Removal of Methylene Blue from Aqueous Solution with Magnetite Loaded Multi-Wall Carbon Nanotube: Kinetic, Isotherm and Mechanism Analysis. J. Hazard. Mater. 2011, 198, 282–290. [Google Scholar] [CrossRef] [PubMed]
  23. Habila, M.A.; Moshab, M.S.; El-Toni, A.M.; ALOthman, Z.A.; Badjah Hadj Ahmed, A.Y. Thermal Fabrication of Magnetic Fe3O4 (Nanoparticle)@Carbon Sheets from Waste Resources for the Adsorption of Dyes: Kinetic, Equilibrium, and UV–Visible Spectroscopy Investigations. Nanomaterials 2023, 13, 1266. [Google Scholar] [CrossRef] [PubMed]
  24. Tishbi, P.; Mosayebi, M.; Salehi, Z.; Fatemi, S.; Faegh, E. Synthesizing Magnetic Graphene Oxide Nanomaterial (GO-Fe3O4) and Kinetic Modelling of Methylene Blue Adsorption from Water. Can. J. Chem. Eng. 2022, 100, 3321–3334. [Google Scholar] [CrossRef]
  25. Wu, K.-H.; Huang, W.-C.; Hung, W.-C.; Tsai, C.-W. Modified Expanded Graphite/Fe3O4 Composite as an Adsorbent of Methylene Blue: Adsorption Kinetics and Isotherms. Mater. Sci. Eng. B 2021, 266, 115068. [Google Scholar] [CrossRef]
  26. Doan, L. Surface Modifications of Superparamagnetic Iron Oxide Nanoparticles with Polyvinyl Alcohol and Graphite as Methylene Blue Adsorbents. Coatings 2023, 13, 1558. [Google Scholar] [CrossRef]
  27. Castro, C.S.; Guerreiro, M.C.; Gonçalves, M.; Oliveira, L.C.A.; Anastácio, A.S. Activated Carbon/Iron Oxide Composites for the Removal of Atrazine from Aqueous Medium. J. Hazard. Mater. 2009, 164, 609–614. [Google Scholar] [CrossRef]
  28. Imamoglu, M.; Yıldız, H.; Altundag, H.; Turhan, Y. Efficient Removal of Cd(II) from Aqueous Solution by Dehydrated Hazelnut Husk Carbon. J. Dispers. Sci. Technol. 2015, 36, 284–290. [Google Scholar] [CrossRef]
  29. Aygun, A.; Yenisoy-Karakas, S.; Duman, I. Production of Granular Activated Carbon from Fruit Stones and Nutshells and Evaluation of Their Physical, Chemical and Adsorption Properties. Microporous Mesoporous Mater. 2003, 66, 189–195. [Google Scholar] [CrossRef]
  30. Senthilkumaar, S.; Varadarajan, P.R.; Porkodi, K.; Subbhuraam, C.V. Adsorption of Methylene Blue onto Jute Fiber Carbon: Kinetics and Equilibrium Studies. J. Colloid. Interface Sci. 2005, 284, 78–82. [Google Scholar] [CrossRef]
  31. Kumar, P.S.; Ramalingam, S.; Sathishkumar, K. Removal of Methylene Blue Dye from Aqueous Solution by Activated Carbon Prepared from Cashew Nut Shell as a New Low-Cost Adsorbent. Korean J. Chem. Eng. 2011, 28, 149–155. [Google Scholar] [CrossRef]
  32. Altundag, H.; Bina, E.; Altıntıg, E. The Levels of Trace Elements in Honey and Molasses Samples That Were Determined by ICP-OES After Microwave Digestion Method. Biol. Trace Elem. Res. 2016, 170, 508–514. [Google Scholar] [CrossRef] [PubMed]
  33. Lelifajri; Nawi, M.A.; Sabar, S.; Supriatno; Nawawi, W.I. Preparation of Immobilized Activated Carbon-Polyvinyl Alcohol Composite for the Adsorptive Removal of 2,4-Dichlorophenoxyacetic Acid. J. Water Process Eng. 2018, 25, 269–277. [Google Scholar] [CrossRef]
  34. Wang, J.; Li, M.; Zhou, S.; Xue, A.; Zhang, Y.; Zhao, Y.; Zhong, J.; Zhang, Q. Graphitic Carbon Nitride Nanosheets Embedded in Poly(Vinyl Alcohol) Nanocomposite Membranes for Ethanol Dehydration via Pervaporation. Sep. Purif. Technol. 2017, 188, 24–37. [Google Scholar] [CrossRef]
  35. Hong, G.; Li, X.; Shen, L.; Wang, M.; Wang, C.; Yu, X.; Wang, X. High Recovery of Lead Ions from Aminated Polyacrylonitrile Nanofibrous Affinity Membranes with Micro/Nano Structure. J. Hazard. Mater. 2015, 295, 161–169. [Google Scholar] [CrossRef] [PubMed]
  36. Alizadeh Fard, M.; Vosoogh, A.; Barkdoll, B.; Aminzadeh, B. Using Polymer Coated Nanoparticles for Adsorption of Micropollutants from Water. Colloids Surf. Physicochem. Eng. Asp. 2017, 531, 189–197. [Google Scholar] [CrossRef]
  37. Wan Ismail, W.I.N.; Ain, S.K.; Zaharudin, R.; Jawad, A.H.; Ishak, M.A.M.; Ismail, K.; Sahid, S. New TiO2/DSAT Immobilization System for Photodegradation of Anionic and Cationic Dyes. Int. J. Photoenergy 2015, 2015, 232741. [Google Scholar] [CrossRef]
  38. Sabri, N.A.; Nawi, M.A.; Nawawi, W.I. Porous Immobilized C Coated N Doped TiO2 Containing In-Situ Generated Polyenes for Enhanced Visible Light Photocatalytic Activity. Opt. Mater. 2015, 48, 258–266. [Google Scholar] [CrossRef]
  39. Tran, H.V.; Bui, L.T.; Dinh, T.T.; Le, D.H.; Huynh, C.D.; Trinh, A.X. Graphene Oxide/Fe3O4/Chitosan Nanocomposite: A Recoverable and Recyclable Adsorbent for Organic Dyes Removal. Application to Methylene Blue. Mater. Res. Express 2017, 4, 035701. [Google Scholar] [CrossRef]
  40. Quach, T.P.T.; Doan, L. Surface Modifications of Superparamagnetic Iron Oxide Nanoparticles with Polyvinyl Alcohol, Chitosan, and Graphene Oxide as Methylene Blue Adsorbents. Coatings 2023, 13, 1333. [Google Scholar] [CrossRef]
  41. Doan, L. Modifying Superparamagnetic Iron Oxide Nanoparticles as Methylene Blue Adsorbents: A Review. ChemEngineering 2023, 7, 77. [Google Scholar] [CrossRef]
  42. Yusuf, M.S.; Sutriyo; Rahmasari, R. Synthesis Processing Condition Optimization of Citrate Stabilized Superparamagnetic Iron Oxide Nanoparticles Using Direct Co-Precipitation Method. Biomed. Pharmacol. J. 2021, 14, 1533–1542. [Google Scholar] [CrossRef]
  43. Loh, K.-S.; Lee, Y.; Musa, A.; Salmah, A.; Zamri, I. Use of Fe3O4 Nanoparticles for Enhancement of Biosensor Response to the Herbicide 2,4-Dichlorophenoxyacetic Acid. Sensors 2008, 8, 5775–5791. [Google Scholar] [CrossRef]
  44. Gong, J.; Lin, X. Facilitated Electron Transfer of Hemoglobin Embedded in Nanosized Fe3O4 Matrix Based on Paraffin Impregnated Graphite Electrode and Electrochemical Catalysis for Trichloroacetic Acid. Microchem. J. 2003, 75, 51–57. [Google Scholar] [CrossRef]
  45. Liao, M.-H.; Chen, D.-H. Immobilization of Yeast Alcohol Dehydrogenase on Magnetic Nanoparticles for Improving Its Stability. Biotechnol. Lett. 2001, 23, 1723–1727. [Google Scholar] [CrossRef]
  46. Deng, J.; Peng, Y.; He, C.; Long, X.; Li, P.; Chan, A.S.C. Magnetic and Conducting Fe3O4-Polypyrrole Nanoparticles with Core-Shell Structure. Polym. Int. 2003, 52, 1182–1187. [Google Scholar] [CrossRef]
  47. Sodipo, B.K.; Aziz, A.A. A Sonochemical Approach to the Direct Surface Functionalization of Superparamagnetic Iron Oxide Nanoparticles with (3-Aminopropyl)Triethoxysilane. Beilstein J. Nanotechnol. 2014, 5, 1472–1476. [Google Scholar] [CrossRef] [PubMed]
  48. Hwang, S.W.; Umar, A.; Dar, G.N.; Kim, S.H.; Badran, R.I. Synthesis and Characterization of Iron Oxide Nanoparticles for Phenyl Hydrazine Sensor Applications. Sens. Lett. 2014, 12, 97–101. [Google Scholar] [CrossRef]
  49. Lopez, J.A.; González, F.; Bonilla, F.A.; Zambrano, G.; Gómez, M.E. Synthesis and Characterization of Fe3O4 Magnetic Nanofluid. Rev. Latinoam. Metal. Mater. 2010, 30, 60–66. [Google Scholar]
  50. Adhikari, M.D.; Mukherjee, S.; Saikia, J.; Das, G.; Ramesh, A. Magnetic Nanoparticles for Selective Capture and Purification of an Antimicrobial Peptide Secreted by Food-Grade Lactic Acid Bacteria. J. Mater. Chem. B 2014, 2, 1432–1438. [Google Scholar] [CrossRef]
  51. Ali, H.; Ismail, A.M. Fabrication of Magnetic Fe3O4/Polypyrrole/Carbon Black Nanocomposite for Effective Uptake of Congo Red and Methylene Blue Dye: Adsorption Investigation and Mechanism. J. Polym. Environ. 2023, 31, 976–998. [Google Scholar] [CrossRef]
  52. Mahmoudi, M.; Simchi, A.; Milani, A.S.; Stroeve, P. Cell Toxicity of Superparamagnetic Iron Oxide Nanoparticles. J. Colloid. Interface Sci. 2009, 336, 510–518. [Google Scholar] [CrossRef] [PubMed]
  53. Mahmoudi, M.; Simchi, A.; Imani, M.; Milani, A.S.; Stroeve, P. Optimal Design and Characterization of Superparamagnetic Iron Oxide Nanoparticles Coated with Polyvinyl Alcohol for Targeted Delivery and Imaging. J. Phys. Chem. B 2008, 112, 14470–14481. [Google Scholar] [CrossRef] [PubMed]
  54. Kostyukova, D.; Chung, Y.H. Synthesis of Iron Oxide Nanoparticles Using Isobutanol. J. Nanomater. 2016, 2016, 4982675. [Google Scholar] [CrossRef]
  55. Kharazmi, A.; Faraji, N.; Mat Hussin, R.; Saion, E.; Yunus, W.M.M.; Behzad, K. Structural, Optical, Opto-Thermal and Thermal Properties of ZnS–PVA Nanofluids Synthesized through a Radiolytic Approach. Beilstein J. Nanotechnol. 2015, 6, 529–536. [Google Scholar] [CrossRef]
  56. Bhat, N.V.; Nate, M.M.; Kurup, M.B.; Bambole, V.A.; Sabharwal, S. Effect of γ-Radiation on the Structure and Morphology of Polyvinyl Alcohol Films. Nucl. Instrum. Methods Phys. Res. Sect. B Beam Interact. Mater. At. 2005, 237, 585–592. [Google Scholar] [CrossRef]
  57. Lee, J.; Isobe, T.; Senna, M. Preparation of Ultrafine Fe3O4 Particles by Precipitation in the Presence of PVA at High pH. J. Colloid. Interface Sci. 1996, 177, 490–494. [Google Scholar] [CrossRef]
  58. Korbag, I.; Mohamed Saleh, S. Studies on the Formation of Intermolecular Interactions and Structural Characterization of Polyvinyl Alcohol/Lignin Film. Int. J. Environ. Stud. 2016, 73, 226–235. [Google Scholar] [CrossRef]
  59. Tang, C.; Shu, Y.; Zhang, R.; Li, X.; Song, J.; Li, B.; Zhang, Y.; Ou, D. Comparison of the Removal and Adsorption Mechanisms of Cadmium and Lead from Aqueous Solution by Activated Carbons Prepared from Typha Angustifolia and Salix Matsudana. RSC Adv. 2017, 7, 16092–16103. [Google Scholar] [CrossRef]
  60. Pochapski, D.J.; Carvalho dos Santos, C.; Leite, G.W.; Pulcinelli, S.H.; Santilli, C.V. Zeta Potential and Colloidal Stability Predictions for Inorganic Nanoparticle Dispersions: Effects of Experimental Conditions and Electrokinetic Models on the Interpretation of Results. Langmuir 2021, 37, 13379–13389. [Google Scholar] [CrossRef]
  61. Bondarenko, L.S.; Kovel, E.S.; Kydralieva, K.A.; Dzhardimalieva, G.I.; Illés, E.; Tombácz, E.; Kicheeva, A.G.; Kudryasheva, N.S. Effects of Modified Magnetite Nanoparticles on Bacterial Cells and Enzyme Reactions. Nanomaterials 2020, 10, 1499. [Google Scholar] [CrossRef]
  62. Soares, S.F.; Fernandes, T.; Trindade, T.; Daniel-da-Silva, A.L. Trimethyl Chitosan/Siloxane-Hybrid Coated Fe3O4 Nanoparticles for the Uptake of Sulfamethoxazole from Water. Molecules 2019, 24, 1958. [Google Scholar] [CrossRef] [PubMed]
  63. Wee, S.-B.; Oh, H.-C.; Kim, T.-G.; An, G.-S.; Choi, S.-C. Role of N-Methyl-2-Pyrrolidone for Preparation of Fe3O4@SiO2 Controlled the Shell Thickness. J. Nanoparticle Res. 2017, 19, 143. [Google Scholar] [CrossRef]
  64. Ma, P.; Luo, Q.; Chen, J.; Gan, Y.; Du, J.; Ding, S.; Xi, Z.; Yang, X. Intraperitoneal Injection of Magnetic Fe3O4-Nanoparticle Induces Hepatic and Renal Tissue Injury via Oxidative Stress in Mice. Int. J. Nanomed. 2012, 7, 4809–4818. [Google Scholar] [CrossRef]
  65. Ferrah, N. Comparative Study of Mercury(II) Species Removal onto Naked and Modified Magnetic Chitosan Flakes Coated Ethylenediaminetetraacetic-Disodium: Kinetic and Thermodynamic Modeling. Environ. Sci. Pollut. Res. 2018, 25, 24923–24938. [Google Scholar] [CrossRef] [PubMed]
  66. Meng, X.; Ryu, J.; Kim, B.; Ko, S. Application of Iron Oxide as a pH-Dependent Indicator for Improving the Nutritional Quality. Clin. Nutr. Res. 2016, 5, 172. [Google Scholar] [CrossRef]
  67. Zhu, A.; Yuan, L.; Liao, T. Suspension of Fe3O4 Nanoparticles Stabilized by Chitosan and O-Carboxymethylchitosan. Int. J. Pharm. 2008, 350, 361–368. [Google Scholar] [CrossRef]
  68. Sotomayor, F.J.; Cychosz, K.A.; Thommes, M. Characterization of Micro/Mesoporous Materials by Physisorption: Concepts and Case Studies. Acc. Mater. Surf. Res. 2018, 3, 34–50. [Google Scholar]
  69. Thommes, M.; Kaneko, K.; Neimark, A.V.; Olivier, J.P.; Rodriguez-Reinoso, F.; Rouquerol, J.; Sing, K.S.W. Physisorption of Gases, with Special Reference to the Evaluation of Surface Area and Pore Size Distribution (IUPAC Technical Report). Pure Appl. Chem. 2015, 87, 1051–1069. [Google Scholar] [CrossRef]
  70. Paramarta, V.; Kristianto, Y.; Taufik, A.; Saleh, R. Improve Sonocatalytic Performance Using Modified Semiconductor Catalyst SnO 2 and ZrO 2 by Magnetite Materials. IOP Conf. Ser. Mater. Sci. Eng. 2017, 188, 012042. [Google Scholar] [CrossRef]
  71. Esmaeili, H.; Tamjidi, S. Ultrasonic-Assisted Synthesis of Natural Clay/Fe3O4/Graphene Oxide for Enhance Removal of Cr (VI) from Aqueous Media. Environ. Sci. Pollut. Res. 2020, 27, 31652–31664. [Google Scholar] [CrossRef]
  72. DemiRel Topel, S.; Gürkan Polat, T. pH-RESPONSIVE CARBOXYMETHYL CELLULOSE CONJUGATED SUPERPARAMAGNETIC IRON OXIDE NANOCARRIERS. J. Sci. Perspect. 2019, 3, 99–110. [Google Scholar] [CrossRef]
  73. Munasir; Kusumawati, R.P. Synthesis and Characterization of Fe3O4@rGO Composite with Wet-Mixing (Ex-Situ) Process. J. Phys. Conf. Ser. 2019, 1171, 012048. [Google Scholar] [CrossRef]
  74. Norouzian Baghani, A.; Mahvi, A.H.; Gholami, M.; Rastkari, N.; Delikhoon, M. One-Pot Synthesis, Characterization and Adsorption Studies of Amine-Functionalized Magnetite Nanoparticles for Removal of Cr (VI) and Ni (II) Ions from Aqueous Solution: Kinetic, Isotherm and Thermodynamic Studies. J. Environ. Health Sci. Eng. 2016, 14, 11. [Google Scholar] [CrossRef] [PubMed]
  75. Heydari Sheikh Hossein, H.; Jabbari, I.; Zarepour, A.; Zarrabi, A.; Ashrafizadeh, M.; Taherian, A.; Makvandi, P. Functionalization of Magnetic Nanoparticles by Folate as Potential MRI Contrast Agent for Breast Cancer Diagnostics. Molecules 2020, 25, 4053. [Google Scholar] [CrossRef] [PubMed]
  76. Yao, Y.; Miao, S.; Liu, S.; Ma, L.P.; Sun, H.; Wang, S. Synthesis, Characterization, and Adsorption Properties of Magnetic Fe3O4@graphene Nanocomposite. Chem. Eng. J. 2012, 184, 326–332. [Google Scholar] [CrossRef]
  77. Yao, Y.; Xu, F.; Chen, M.; Xu, Z.; Zhu, Z. Adsorption Behavior of Methylene Blue on Carbon Nanotubes. Bioresour. Technol. 2010, 101, 3040–3046. [Google Scholar] [CrossRef]
  78. Pigatto, G.; Lodi, A.; Finocchio, E.; Palma, M.S.A.; Converti, A. Chitin as Biosorbent for Phenol Removal from Aqueous Solution: Equilibrium, Kinetic and Thermodynamic Studies. Chem. Eng. Process. Process Intensif. 2013, 70, 131–139. [Google Scholar] [CrossRef]
  79. Seki, Y.; Yurdakoç, K. Adsorption of Promethazine Hydrochloride with KSF Montmorillonite. Adsorption 2006, 12, 89–100. [Google Scholar] [CrossRef]
  80. Sharma, P.; Kaur, R.; Baskar, C.; Chung, W.-J. Removal of Methylene Blue from Aqueous Waste Using Rice Husk and Rice Husk Ash. Desalination 2010, 259, 249–257. [Google Scholar] [CrossRef]
  81. Peydayesh, M.; Rahbar-Kelishami, A. Adsorption of Methylene Blue onto Platanus Orientalis Leaf Powder: Kinetic, Equilibrium and Thermodynamic Studies. J. Ind. Eng. Chem. 2015, 21, 1014–1019. [Google Scholar] [CrossRef]
  82. Nekouei, F.; Nekouei, S.; Tyagi, I.; Gupta, V.K. Kinetic, Thermodynamic and Isotherm Studies for Acid Blue 129 Removal from Liquids Using Copper Oxide Nanoparticle-Modified Activated Carbon as a Novel Adsorbent. J. Mol. Liq. 2015, 201, 124–133. [Google Scholar] [CrossRef]
  83. Luo, X.-P.; Fu, S.-Y.; Du, Y.-M.; Guo, J.-Z.; Li, B. Adsorption of Methylene Blue and Malachite Green from Aqueous Solution by Sulfonic Acid Group Modified MIL-101. Microporous Mesoporous Mater. 2017, 237, 268–274. [Google Scholar] [CrossRef]
  84. Sharma, P.; Hussain, N.; Borah, D.J.; Das, M.R. Kinetics and Adsorption Behavior of the Methyl Blue at the Graphene Oxide/Reduced Graphene Oxide Nanosheet–Water Interface: A Comparative Study. J. Chem. Eng. Data 2013, 58, 3477–3488. [Google Scholar] [CrossRef]
  85. Ai, L.; Li, M.; Li, L. Adsorption of Methylene Blue from Aqueous Solution with Activated Carbon/Cobalt Ferrite/Alginate Composite Beads: Kinetics, Isotherms, and Thermodynamics. J. Chem. Eng. Data 2011, 56, 3475–3483. [Google Scholar] [CrossRef]
  86. Karaer, H.; Kaya, İ. Synthesis, Characterization of Magnetic Chitosan/Active Charcoal Composite and Using at the Adsorption of Methylene Blue and Reactive Blue4. Microporous Mesoporous Mater. 2016, 232, 26–38. [Google Scholar] [CrossRef]
  87. Singh, D. Studies of the Adsorption Thermodynamics of Oxamyl on Fly Ash. Adsorpt. Sci. Technol. 2000, 18, 741–748. [Google Scholar] [CrossRef]
  88. Özcan, A.; Öncü, E.M.; Özcan, A.S. Kinetics, Isotherm and Thermodynamic Studies of Adsorption of Acid Blue 193 from Aqueous Solutions onto Natural Sepiolite. Colloids Surf. Physicochem. Eng. Asp. 2006, 277, 90–97. [Google Scholar] [CrossRef]
  89. Bhattacharyya, K.G.; Sharma, A. Kinetics and Thermodynamics of Methylene Blue Adsorption on Neem (Azadirachta Indica) Leaf Powder. Dye. Pigment. 2005, 65, 51–59. [Google Scholar] [CrossRef]
  90. Umoren, S.A.; Etim, U.J.; Israel, A.U. Adsorption of Methylene Blue from Industrial Effluent Using Poly (Vinyl Alcohol). J. Mater. Environ. Sci. 2013, 4, 75–86. [Google Scholar]
  91. Ofomaja, A.E.; Ho, Y.-S. Equilibrium Sorption of Anionic Dye from Aqueous Solution by Palm Kernel Fibre as Sorbent. Dye. Pigment. 2007, 74, 60–66. [Google Scholar] [CrossRef]
  92. Dai, H.; Huang, Y.; Huang, H. Eco-Friendly Polyvinyl Alcohol/Carboxymethyl Cellulose Hydrogels Reinforced with Graphene Oxide and Bentonite for Enhanced Adsorption of Methylene Blue. Carbohydr. Polym. 2018, 185, 1–11. [Google Scholar] [CrossRef] [PubMed]
  93. Bulut, Y.; Aydın, H. A Kinetics and Thermodynamics Study of Methylene Blue Adsorption on Wheat Shells. Desalination 2006, 194, 259–267. [Google Scholar] [CrossRef]
  94. Dai, H.; Huang, H. Synthesis, Characterization and Properties of Pineapple Peel Cellulose-g-Acrylic Acid Hydrogel Loaded with Kaolin and Sepia Ink. Cellulose 2017, 24, 69–84. [Google Scholar] [CrossRef]
  95. Sekhavat Pour, Z.; Ghaemy, M. Removal of Dyes and Heavy Metal Ions from Water by Magnetic Hydrogel Beads Based on Poly(Vinyl Alcohol)/Carboxymethyl Starch-g-Poly(Vinyl Imidazole). RSC Adv. 2015, 5, 64106–64118. [Google Scholar] [CrossRef]
  96. Sharma, G.; Naushad, M.; Al-Muhtaseb, A.H.; Kumar, A.; Khan, M.R.; Kalia, S.; Shweta; Bala, M.; Sharma, A. Fabrication and Characterization of Chitosan-Crosslinked-Poly(Alginic Acid) Nanohydrogel for Adsorptive Removal of Cr(VI) Metal Ion from Aqueous Medium. Int. J. Biol. Macromol. 2017, 95, 484–493. [Google Scholar] [CrossRef]
  97. Sharma, G.; Kumar, A.; Devi, K.; Sharma, S.; Naushad, M.; Ghfar, A.A.; Ahamad, T.; Stadler, F.J. Guar Gum-Crosslinked-Soya Lecithin Nanohydrogel Sheets as Effective Adsorbent for the Removal of Thiophanate Methyl Fungicide. Int. J. Biol. Macromol. 2018, 114, 295–305. [Google Scholar] [CrossRef]
  98. Sharma, G.; Kumar, A.; Naushad, M.; García-Peñas, A.; Al-Muhtaseb, A.H.; Ghfar, A.A.; Sharma, V.; Ahamad, T.; Stadler, F.J. Fabrication and Characterization of Gum Arabic-Cl-Poly(Acrylamide) Nanohydrogel for Effective Adsorption of Crystal Violet Dye. Carbohydr. Polym. 2018, 202, 444–453. [Google Scholar] [CrossRef]
  99. Ma, J.; Huang, D.; Zou, J.; Li, L.; Kong, Y.; Komarneni, S. Adsorption of Methylene Blue and Orange II Pollutants on Activated Carbon Prepared from Banana Peel. J. Porous Mater. 2015, 22, 301–311. [Google Scholar] [CrossRef]
  100. Hameed, B.H.; Din, A.T.M.; Ahmad, A.L. Adsorption of Methylene Blue onto Bamboo-Based Activated Carbon: Kinetics and Equilibrium Studies. J. Hazard. Mater. 2007, 141, 819–825. [Google Scholar] [CrossRef]
  101. Theydan, S.K.; Ahmed, M.J. Adsorption of Methylene Blue onto Biomass-Based Activated Carbon by FeCl3 Activation: Equilibrium, Kinetics, and Thermodynamic Studies. J. Anal. Appl. Pyrolysis 2012, 97, 116–122. [Google Scholar] [CrossRef]
  102. Hameed, B.H.; Ahmad, A.L.; Latiff, K.N.A. Adsorption of Basic Dye (Methylene Blue) onto Activated Carbon Prepared from Rattan Sawdust. Dye. Pigment. 2007, 75, 143–149. [Google Scholar] [CrossRef]
  103. Bestani, B.; Benderdouche, N.; Benstaali, B.; Belhakem, M.; Addou, A. Methylene Blue and Iodine Adsorption onto an Activated Desert Plant. Bioresour. Technol. 2008, 99, 8441–8444. [Google Scholar] [CrossRef] [PubMed]
  104. El Qada, E.N.; Allen, S.J.; Walker, G.M. Adsorption of Methylene Blue onto Activated Carbon Produced from Steam Activated Bituminous Coal: A Study of Equilibrium Adsorption Isotherm. Chem. Eng. J. 2006, 124, 103–110. [Google Scholar] [CrossRef]
  105. Foo, K.Y.; Hameed, B.H. Microwave-Assisted Preparation of Oil Palm Fiber Activated Carbon for Methylene Blue Adsorption. Chem. Eng. J. 2011, 166, 792–795. [Google Scholar] [CrossRef]
  106. Belhachemi, M.; Addoun, F. Comparative Adsorption Isotherms and Modeling of Methylene Blue onto Activated Carbons. Appl. Water Sci. 2011, 1, 111–117. [Google Scholar] [CrossRef]
  107. Deng, H.; Yang, L.; Tao, G.; Dai, J. Preparation and Characterization of Activated Carbon from Cotton Stalk by Microwave Assisted Chemical Activation—Application in Methylene Blue Adsorption from Aqueous Solution. J. Hazard. Mater. 2009, 166, 1514–1521. [Google Scholar] [CrossRef]
  108. Vargas, A.M.M.; Cazetta, A.L.; Kunita, M.H.; Silva, T.L.; Almeida, V.C. Adsorption of Methylene Blue on Activated Carbon Produced from Flamboyant Pods (Delonix Regia): Study of Adsorption Isotherms and Kinetic Models. Chem. Eng. J. 2011, 168, 722–730. [Google Scholar] [CrossRef]
  109. Wang, S.; Boyjoo, Y.; Choueib, A. A Comparative Study of Dye Removal Using Fly Ash Treated by Different Methods. Chemosphere 2005, 60, 1401–1407. [Google Scholar] [CrossRef]
  110. Tsai, W.T.; Yang, J.M.; Lai, C.W.; Cheng, Y.H.; Lin, C.C.; Yeh, C.W. Characterization and Adsorption Properties of Eggshells and Eggshell Membrane. Bioresour. Technol. 2006, 97, 488–493. [Google Scholar] [CrossRef]
  111. Banerjee, S.; Dastidar, M.G. Use of Jute Processing Wastes for Treatment of Wastewater Contaminated with Dye and Other Organics. Bioresour. Technol. 2005, 96, 1919–1928. [Google Scholar] [CrossRef]
  112. Garg, V.K.; Amita, M.; Kumar, R.; Gupta, R. Basic Dye (Methylene Blue) Removal from Simulated Wastewater by Adsorption Using Indian Rosewood Sawdust: A Timber Industry Waste. Dye. Pigment. 2004, 63, 243–250. [Google Scholar] [CrossRef]
  113. Fytianos, K.; Voudrias, E.; Kokkalis, E. Sorption–Desorption Behaviour of 2,4-Dichlorophenol by Marine Sediments. Chemosphere 2000, 40, 3–6. [Google Scholar] [CrossRef]
  114. Reed, B.E.; Matsumoto, M.R. Modeling Cadmium Adsorption by Activated Carbon Using the Langmuir and Freundlich Isotherm Expressions. Sep. Sci. Technol. 1993, 28, 2179–2195. [Google Scholar] [CrossRef]
  115. Samrot, A.V.; Ali, H.H.; Selvarani, J.; Faradjeva, E.; Raji, P.; Prakash, P.; Kumar S, S. Adsorption Efficiency of Chemically Synthesized Superparamagnetic Iron Oxide Nanoparticles (SPIONs) on Crystal Violet Dye. Curr. Res. Green. Sustain. Chem. 2021, 4, 100066. [Google Scholar] [CrossRef]
  116. Üner, O.; Geçgel, Ü.; Bayrak, Y. Adsorption of Methylene Blue by an Efficient Activated Carbon Prepared from Citrullus Lanatus Rind: Kinetic, Isotherm, Thermodynamic, and Mechanism Analysis. Water. Air. Soil. Pollut. 2016, 227, 247. [Google Scholar] [CrossRef]
  117. Sheha, R.R.; Metwally, E. Equilibrium Isotherm Modeling of Cesium Adsorption onto Magnetic Materials. J. Hazard. Mater. 2007, 143, 354–361. [Google Scholar] [CrossRef] [PubMed]
  118. Chabani, M.; Amrane, A.; Bensmaili, A. Kinetic Modelling of the Adsorption of Nitrates by Ion Exchange Resin. Chem. Eng. J. 2006, 125, 111–117. [Google Scholar] [CrossRef]
  119. Özcan, A.; Özcan, A.S.; Tunali, S.; Akar, T.; Kiran, I. Determination of the Equilibrium, Kinetic and Thermodynamic Parameters of Adsorption of Copper(II) Ions onto Seeds of Capsicum Annuum. J. Hazard. Mater. 2005, 124, 200–208. [Google Scholar] [CrossRef]
  120. Helfferich, F.G. Ion Exchange; Courier Corporation: Chelmsford, MA, USA, 1995; ISBN 978-0-486-68784-1. [Google Scholar]
  121. Onyango, M.S.; Kojima, Y.; Aoyi, O.; Bernardo, E.C.; Matsuda, H. Adsorption Equilibrium Modeling and Solution Chemistry Dependence of Fluoride Removal from Water by Trivalent-Cation-Exchanged Zeolite F-9. J. Colloid. Interface Sci. 2004, 279, 341–350. [Google Scholar] [CrossRef]
  122. Tan, I.A.W.; Ahmad, A.L.; Hameed, B.H. Adsorption of Basic Dye on High-Surface-Area Activated Carbon Prepared from Coconut Husk: Equilibrium, Kinetic and Thermodynamic Studies. J. Hazard. Mater. 2008, 154, 337–346. [Google Scholar] [CrossRef]
  123. Liu, Y.; Bai, Q.; Lou, S.; Di, D.; Li, J.; Guo, M. Adsorption Characteristics of (−)-Epigallocatechin Gallate and Caffeine in the Extract of Waste Tea on Macroporous Adsorption Resins Functionalized with Chloromethyl, Amino, and Phenylamino Groups. J. Agric. Food Chem. 2012, 60, 1555–1566. [Google Scholar] [CrossRef] [PubMed]
  124. Al-Ghouti, M.A.; Da’ana, D.A. Guidelines for the Use and Interpretation of Adsorption Isotherm Models: A Review. J. Hazard. Mater. 2020, 393, 122383. [Google Scholar] [CrossRef] [PubMed]
  125. Jawad, A.H.; Surip, S.N. Upgrading Low Rank Coal into Mesoporous Activated Carbon via Microwave Process for Methylene Blue Dye Adsorption: Box Behnken Design and Mechanism Study. Diam. Relat. Mater. 2022, 127, 109199. [Google Scholar] [CrossRef]
  126. Jawad, A.H.; Ismail, K.; Ishak, M.A.M.; Wilson, L.D. Conversion of Malaysian Low-Rank Coal to Mesoporous Activated Carbon: Structure Characterization and Adsorption Properties. Chin. J. Chem. Eng. 2019, 27, 1716–1727. [Google Scholar] [CrossRef]
  127. Jawad, A.H.; Mohd Firdaus Hum, N.N.; Abdulhameed, A.S.; Mohd Ishak, M.A. Mesoporous Activated Carbon from Grass Waste via H3PO4-Activation for Methylene Blue Dye Removal: Modelling, Optimisation, and Mechanism Study. Int. J. Environ. Anal. Chem. 2020, 102, 6061–6077. [Google Scholar] [CrossRef]
  128. Kannan, N.; Sundaram, M.M. Kinetics and Mechanism of Removal of Methylene Blue by Adsorption on Various Carbons—A Comparative Study. Dye. Pigment. 2001, 51, 25–40. [Google Scholar] [CrossRef]
Figure 1. (a) FE-SEM image of IONPs. (b) the normal size distribution of IONPs.
Figure 1. (a) FE-SEM image of IONPs. (b) the normal size distribution of IONPs.
Magnetochemistry 09 00211 g001
Figure 2. FE-SEM images of IONPs/PVA/AC 3:4:12 at (a) 5 μm, (b) 1 μm, (c) 500 nm, (d) the proposed structure of the adsorbents.
Figure 2. FE-SEM images of IONPs/PVA/AC 3:4:12 at (a) 5 μm, (b) 1 μm, (c) 500 nm, (d) the proposed structure of the adsorbents.
Magnetochemistry 09 00211 g002
Figure 3. X-ray diffractogram of (a) SPION, (b) overlay diffractograms of SPION (black), PVA (green), AC (blue), and SPION/PVA/AC (red).
Figure 3. X-ray diffractogram of (a) SPION, (b) overlay diffractograms of SPION (black), PVA (green), AC (blue), and SPION/PVA/AC (red).
Magnetochemistry 09 00211 g003
Figure 4. (a) FTIR spectra of SPION (black), PVA (green), AC (blue), and SPION/PVA/AC (red). (b) The BET result of relative pressure over volume of SPION/PVA/AC. (c) VSM result of SPION (black) and SPION/PVA/AC (red).
Figure 4. (a) FTIR spectra of SPION (black), PVA (green), AC (blue), and SPION/PVA/AC (red). (b) The BET result of relative pressure over volume of SPION/PVA/AC. (c) VSM result of SPION (black) and SPION/PVA/AC (red).
Magnetochemistry 09 00211 g004aMagnetochemistry 09 00211 g004b
Figure 5. Adsorption capacity (mg/g) over time at (a) 273.15 K, (b) 310.15 K, (c) 333.15 K.
Figure 5. Adsorption capacity (mg/g) over time at (a) 273.15 K, (b) 310.15 K, (c) 333.15 K.
Magnetochemistry 09 00211 g005
Figure 6. The Langmuir adsorption isotherm model at (a) 273.15 K, (b) 310.15 K, and (c) 333.15 K.
Figure 6. The Langmuir adsorption isotherm model at (a) 273.15 K, (b) 310.15 K, and (c) 333.15 K.
Magnetochemistry 09 00211 g006
Figure 7. The Freundlich adsorption isotherm model at (a) 273.15 K, (b) 310.15 K, and (c) 333.15 K.
Figure 7. The Freundlich adsorption isotherm model at (a) 273.15 K, (b) 310.15 K, and (c) 333.15 K.
Magnetochemistry 09 00211 g007
Figure 8. The Dubinin–Radushkevich adsorption isotherm model at (a) 273.15 K, (b) 310.15 K, (c) 333.15 K.
Figure 8. The Dubinin–Radushkevich adsorption isotherm model at (a) 273.15 K, (b) 310.15 K, (c) 333.15 K.
Magnetochemistry 09 00211 g008
Figure 9. The Temkin and Pyzhev adsorption isotherm model at (a) 273.15 K, (b) 310.15 K, and (c) 333.15 K.
Figure 9. The Temkin and Pyzhev adsorption isotherm model at (a) 273.15 K, (b) 310.15 K, and (c) 333.15 K.
Magnetochemistry 09 00211 g009
Figure 10. The Halsey adsorption isotherm model at (a) 273.15 K, (b) 310.15 K, and (c) 333.15 K.
Figure 10. The Halsey adsorption isotherm model at (a) 273.15 K, (b) 310.15 K, and (c) 333.15 K.
Magnetochemistry 09 00211 g010
Figure 11. The intraparticle diffusion model at (a) 273.15 K, (b) 310.15 K, (c) 333.15 K.
Figure 11. The intraparticle diffusion model at (a) 273.15 K, (b) 310.15 K, (c) 333.15 K.
Magnetochemistry 09 00211 g011
Table 1. BJH and BET analyses of the SPION/PVA/AC samples.
Table 1. BJH and BET analyses of the SPION/PVA/AC samples.
Surface area (m2/g)751
Pore diameter (Amstrong)10
Pore volume (cm3/g)0.38
Table 2. The Q t , %LC, and %EE after 24 h of adsorption.
Table 2. The Q t , %LC, and %EE after 24 h of adsorption.
Initial MB Concentration (mg/mL) Q t (mg/g)%LC (%)%EE (%)
333.15 K
0.01730.31 ± 2.513.03 ± 0.2587.69 ± 4.56
0.01829.16 ± 1.272.92 ± 0.1385.39 ± 1.11
0.01933.13 ± 2.223.31 ± 0.2292.09 ± 1.42
0.02037.48 ± 3.453.75 ± 0.3594.35 ± 1.72
310.15 K
0.01727.91 ± 0.412.79 ± 0.0479.97 ± 2.11
0.01828.33 ± 1.662.83 ± 0.1778.95 ± 2.97
0.01931.31 ± 1.603.13 ± 0.1674.04 ± 7.38
0.02035.04 ± 0.773.50 ± 0.0881.57 ± 1.84
298.15 K
0.01718.64 ± 0.791.86 ± 0.0855.21 ± 2.52
0.01821.85 ± 1.202.18 ± 0.1257.91 ± 2.50
0.01925.31 ± 0.972.53 ± 0.1057.22 ± 1.78
0.02021.75 ± 1.032.17 ± 0.1056.53 ± 0.93
Table 3. Thermodynamic parameters after 69 h adsorption.
Table 3. Thermodynamic parameters after 69 h adsorption.
Temperature (K) G (J/mol) H (J/mol) S (J/mol K)
Table 4. The Q t , %LC, %EE after 69 h adsorption.
Table 4. The Q t , %LC, %EE after 69 h adsorption.
Initial MB Concentration (mg/mL) Q t (mg/g)%LC (%)%EE (%)
333.15 K
0.01733.99 ± 1.303.40 ± 0.1398.46 ± 0.99
0.01833.37 ± 1.133.34 ± 0.1197.76 ± 1.00
0.01935.45 ± 1.843.55 ± 0.1898.63 ± 0.23
0.02039.22 ± 4.033.92 ± 0.4098.60 ± 0.72
310.15 K
0.01732.74 ± 0.423.27 ± 0.0493.80 ± 0.96
0.01833.33 ± 1.623.33 ± 0.1692.89 ± 2.17
0.01937.17 ± 0.523.72 ± 0.0587.72 ± 5.54
0.02040.21 ± 1.304.02 ± 0.1393.57 ± 1.29
298.15 K
0.01726.50 ± 0.992.65 ± 0.1078.50 ± 3.42
0.01830.09 ± 1.693.01 ± 0.1779.75 ± 3.41
0.01934.72 ± 1.503.47 ± 0.1578.50 ± 2.68
0.02031.33 ± 0.973.13 ± 0.1081.47 ± 1.07
Table 5. Kinetic models after 69 h adsorption.
Table 5. Kinetic models after 69 h adsorption.
Initial MB Concentration (mg/mL)
333.15 K
Pseudo-first order Q e
mg MB (g particles)−1
(g mg−1 min−1)
χ 2 0.240.360.090.05
Q e
mg MB (g particles)−1
(g mg−1 day−1)
χ 2 0.0080.0340.0050.005
(mg/(g day))
310.15 K
Pseudo-first order Q e
mg MB (g particles)−1
(g mg−1 min−1)
χ 2 0.440.480.550.40
Pseudo-second order Q e
mg MB (g particles)−1
(g mg−1 day−1)
χ 2
(mg/(g day))
273.15 K
Pseudo-first order Q e
mg MB (g particles)−1
(g mg−1 min−1)
χ 2 1.391.531.511.73
Pseudo-second order Q e
mg MB (g particles)−1
(g mg−1 day−1)
χ 2 0.070.340.100.05
(mg/(g day))
Table 6. Adsorption isotherms model constants and variables.
Table 6. Adsorption isotherms model constants and variables.
ModelConstant298.15 K310.15 K333.15 K
LangmuirkL (L/mg)−0.0332.58
Q0 (mg/g)−243.9042.1924.51
Average RL1.00 ± 3 × 10−50.95 ± 0.0030.95 ± 0.003
FreundlichkF (mg/g)2.284.524.83
1 n F (mg/L)1.170.18−0.28
Dubinin–RadushkevichkDR (mol2 J2)20.02−0.09
Qm (mg/g)59.1840.1926.70
E (kJ mol−1)2507142.86−5555.56
Temkin and PyzhevB137.946.39−9.47
kTP (mg/g)−0.495.04−3.96
kHa5.071.71 × 1082.84 × 10−6
Table 7. The intraparticle diffusion model after 96 h.
Table 7. The intraparticle diffusion model after 96 h.
Initial MB Concentration (mg/mL)kII
298.15 K
310.15 K
333.15 K
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Doan, L. Surface Modifications of Superparamagnetic Iron Oxide Nanoparticles with Polyvinyl Alcohol and Activated Charcoal as Methylene Blue Adsorbents. Magnetochemistry 2023, 9, 211.

AMA Style

Doan L. Surface Modifications of Superparamagnetic Iron Oxide Nanoparticles with Polyvinyl Alcohol and Activated Charcoal as Methylene Blue Adsorbents. Magnetochemistry. 2023; 9(9):211.

Chicago/Turabian Style

Doan, Linh. 2023. "Surface Modifications of Superparamagnetic Iron Oxide Nanoparticles with Polyvinyl Alcohol and Activated Charcoal as Methylene Blue Adsorbents" Magnetochemistry 9, no. 9: 211.

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop