Skip to main content
NCBI home page
RSC Advances logoLink to RSC Advances
. 2026 Sep 25. Online ahead of print. doi: 10.1039/d6ra08198c

Removal of methylene blue dye from aqueous solutions by adsorption onto new 1,3-dibromopropane crosslinked Schiff base chitosan/CoFe2O4/SiO2 nanocomposite

Afshin Saadat a,✉, Alireza Banaei b, Mahtab Ghanifathi b, Parinaz Pargol Ghasemi b
PMCID: PMC13614486  PMID: 42799227

Abstract

In this study, a novel modified Schiff base chitosan/1,3-dibromopropane/4-hydroxybenzaldehyde/CoFe2O4/SiO2 (Cs-DBP-HBA-CoFe2O4-SiO2) nanocomposite was synthesized. The synthesized nanocomposite was analyzed using Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), vibrating sample magnetometry (VSM), energy-dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) techniques. The synthesized nanocomposite was utilized as an efficient adsorbent for removing methylene blue (MB) from aqueous solutions via the batch adsorption method. Various parameters, including pH, contact time, adsorbent dosage, and initial dye concentration, were investigated. The optimized adsorption parameters were determined to be an adsorbent dose of 40 mg L−1, an initial dye concentration of 100 mg L−1, pH = 3, and a contact time of 30 min. Adsorption studies revealed that the methylene blue uptake by the synthesized nanocomposite is a highly favorable process (RL and n values within the favorable range) occurring on a heterogeneous surface (R2 = 0.9729). The mechanism is primarily governed by physisorption involving non-covalent interactions, such as hydrogen bonding and pi–pi stacking, rather than chemisorption. Additionally, the divergence in maximum adsorption capacities (qm) calculated via Langmuir model. Kinetic studies demonstrated that the adsorption followed the pseudo-first-order model, suggesting that the rate-limiting step is physisorption mechanism. Thermodynamic analysis indicated that the adsorption of MB onto the nanocomposite was an endothermic and spontaneous process.

In this study, a novel modified Schiff base chitosan/1,3-dibromopropane/4-hydroxybenzaldehyde/CoFe2O4/SiO2 (Cs-DBP-HBA-CoFe2O4-SiO2) nanocomposite was synthesized.graphic file with name d6ra08198c-ga.webp

1. Introduction

One of the most pressing global issues is water pollution, making the removal or prevention of pollutant discharge essential.1–4 One of the most critical water pollutants stemming from various industrial activities is organic dyes.5–7 These dyes can affect the ecosystem and cause widespread damage. Due to the environmental challenges and the costs involved, it is necessary to develop new, highly efficient techniques to eliminate dyes from wastewater.8,9 Several conventional methods have been extensively utilized for the degradation of toxic dyes, such as chemical precipitation, membrane filtration, flotation, oxidation–reduction, ozonation, coagulation–flocculation, and various biological processes. Despite their widespread use, these techniques frequently encounter limitations regarding high operational costs, energy intensity, and limited efficiency in completely eliminating persistent pollutants. Among these diverse methodologies, adsorption stands out as a highly efficient and economical approach, characterized by its operational ease, high selectivity, and robust potential for the removal of organic dyes from industrial wastewater.10,11 To date, various techniques and materials have been employed for the degradation and removal of organic dyes from aqueous solutions.12–21 Among the various available techniques, adsorption stands out as one of the most promising methods due to its simplicity, high efficiency, and cost-effectiveness.22–24 To ensure the efficient removal of dyes from wastewater, adsorbents must possess several key characteristics, including high surface area, strong binding affinity for pollutants, cost-effectiveness, non-toxicity, eco-friendliness, and recyclability.25–28 Among these, magnetic nanoparticles have garnered significant attention due to their chemical stability, large surface area, low toxicity, excellent biocompatibility, and biodegradability.29–32 Ferrites, characterized by the general formula MFe2O4, commonly comprise various metal cations, including Ba2+, Ca2+, Co2+, Cu2+, Mg2+, Mn2+, and Ni2+. Owing to their unique physicochemical properties, ferrites represent a significant class of compounds with diverse applications in the degradation of various water pollutants. Their favorable optical band gap, spinel crystal structure, chemical and thermal stability, high specific surface area, and distinct magnetic properties render them excellent candidates for photocatalytic applications.33 The remarkable properties of cobalt ferrite including its chemical stability, mechanical hardness, and efficient magnetic recovery have prompted numerous studies focusing on its application in wastewater treatment.34 Recently, extensive research has focused on the development of alternative adsorbents, with a particular emphasis on polymer-based materials. Chitosan (Cs) and its derivatives are widely utilized for organic dye removal, attributed to various functional groups present on their surface, such as OH and NH2. Due to its non-toxic, biodegradable, biocompatible, and antibacterial properties, chitosan exhibits a wide range of applications across the cosmetic, food, and textile industries.35–38 In acidic media, the amino groups of chitosan undergo easy protonation, leading to the solubilization of the positively charged polymer chains. Consequently, the crosslinking of chitosan with various agents has been extensively investigated to enhance its chemical stability under acidic conditions, thereby facilitating the efficient removal of dyes from aqueous solutions.39,40 In this work, new modified Schiff base chitosan/1,3-dibromopropane/CoFe2O4/SiO2 nanocomposite (Fig. 1) were prepared. The nanocomposite was used for the removal of the methylene blue from aqueous solution. The influence of factors such as pH, adsorbent dosage, initial dye concentration, and contact time on the adsorption behavior was examined. Also, the equilibrium isotherms were determined and explained.

Fig. 1. Schematic illustration of modified chitosan Schiff base nanocomposite (Cs-DBP-HBA-CoFe2O4-SiO2) preparation.

Fig. 1

Open in a new tab

2. Experimental

2.1. Materials and methods

FT-IR spectra were obtained on a Shimadzu Prestige-21 spectrometer over the 400–4000 cm−1 range using KBr pellets at room temperature. Powder X-ray diffraction (XRD) patterns were collected with a PerkinElmer X-ray diffractometer at ambient temperature. The morphology, particle size, and structural features of the compounds were examined using Field Emission Scanning Electron Microscopy (FESEM). Magnetic properties were characterized via vibrating sample magnetometry (VSM) using a VSM 7407 magnetometer at room temperature. Thermogravimetric analysis (TGA) was performed using a PerkinElmer analyzer from 20 to 700 °C at a heating rate of 20 °C min−1 under an N2 atmosphere. Additionally, UV-vis spectra were obtained via a PerkinElmer Lambda 45 spectrophotometer. pH measurements were performed using a Jenway 4510 pH meter equipped with a combined electrode. Elemental composition was analyzed via Energy Dispersive X-ray (EDX) spectroscopy, utilizing a Delta series KEVEX spectrometer integrated with a Hitachi S-800 SEM. Furthermore, the specific surface area of the samples was determined by the BET method through N2 sorption analysis at 77 K, using a Micromeritics ASAP 2010 accelerated surface area and porosimetry system.

2.2. Preparation of the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite

2.2.1. Synthesis of cobalt ferrite nanoparticles CoFe2O4 nanoparticles

FeCl3·6H2O (2.63 g) and CoCl2·6H2O (2.18 g) were dissolved in 100 mL of deionized water. The solution was then maintained at 80 °C for 60 min under continuous mechanical stirring. Finally, the CoFe2O4 nanoparticles were isolated using an external magnet, washed several times with deionized water and ethanol, and subsequently dried at 60 °C for 24 h.

2.2.2. Synthesis of silica-coated nanoparticles CoFe2O4-SiO2

CoFe2O4 (2 g) was dispersed in 50 mL of 0.1 M HCl aqueous solution and sonicated for 15 min. Subsequently, the nanoparticles were suspended in a mixture of 50 mL deionized water, 80 mL ethanol, and 5 mL of 32% ammonia solution, followed by stirring for 2 h. Tetraethyl orthosilicate (TEOS) (15 mL) dissolved in 10 mL of ethanol was then introduced to the suspension and stirred at room temperature for 24 h. Finally, the CoFe2O4-SiO2 nanoparticles were isolated via magnetic separation and washed thoroughly with ethanol and deionized water.

2.2.3. Synthesis of Cs-DBP-HBA

Chitosan (0.75 g) was weighed using a digital balance and transferred into a round-bottom flask. To this, 25 mL of an acetic acid–ethanol solution (95 : 5 w/w) was added. After stirring for 20 min using a magnetic stirrer, with a reflux condenser fitted as a stopper, 1 g of 1,3-dibromopropane was introduced, and the mixture was stirred for 24 h at room temperature. Separately, 0.672 g of 4-hydroxybenzaldehyde was dissolved in ethanol in a small beaker under heating, and then added dropwise to the reaction mixture in the flask. The flask was placed in an oil bath, and the mixture was stirred for 24 h at 50–60 °C. After the reaction, the magnetic stirrer was removed, and the precipitate was allowed to settle. The product was then isolated via decantation, washed with a small amount of ethanol, and dried at room temperature.

2.2.4. Synthesis of Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite

A mixture containing 0.5 g of the product (Cs-DBP-HBA), 70 mL of ethanol, and 0.25 g of brown CoFe2O4-SiO2 nanoparticles was transferred into a round-bottom flask. The flask was placed in an oil bath equipped with a thermometer and stirred using a magnetic stirrer for 3 h. To remove oxygen from the reaction environment, a reflux condenser was attached to the flask, and a nitrogen-filled balloon was connected to the system to maintain an inert atmosphere, following the same procedure as the previous synthesis. The mixture was then subjected to reflux for 24 h at approximately 80 °C with a stirring speed of 200 rpm. The resulting solid was washed three times with ethanol and distilled water, and finally, it was left in the laboratory environment to undergo complete drying.

2.3. Adsorption experiments

The removal of methylene blue (MB) dye from aqueous media was investigated using a synthesized Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite. To facilitate the experiments, a 1000 mg L−1 stock solution of MB was prepared in deionized water and subsequently diluted to various concentrations. The adsorption efficiency was systematically evaluated by investigating the effects of several parameters. Specifically, the influence of adsorbent dosage was studied by suspending 10–80 mg of the nanocomposite in 10 mL of 100 mg L−1 dye solution at 25 °C for 30 minutes. The impact of initial dye concentration was assessed at room temperature by varying the concentration from 20 to 150 mg L−1 while maintaining all other variables constant. Additionally, the effect of contact time was examined over a range of 10 to 60 minutes, with the adsorbent dosage fixed at 40 mg. Finally, the solution pH was adjusted using 0.01 N HCl or NaOH to evaluate its role in the dye removal process. The concentration of the MB was analyzed by UV-spectrophotometer at λmax 600 nm. The amount of the dye adsorbed onto adsorbent (qe in mg g−1) and the percentage of the dyes removed from the solution (R in %) were calculated from the eqn (1) and (2):

2.3. 1
2.3. 2

where, C0 and Ce are the initial and equilibrium concentration of dye in solution (mg L−1), respectively. V is the initial volume of the dye solution (L) and M is the mass of adsorbent used (g).

3. Results and discussion

3.1. FT-IR analysis

In this study, chitosan was functionalized using 1,3-dibromopropane, 4-hydroxybenzaldehyde, and CoFe2O4-SiO2 nanoparticles. Fig. 2 illustrates the FT-IR spectrum of the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite within the wavenumber range of 4000 to 400 cm−1. Fig. 2a displays the FT-IR spectrum of the CoFe2O4 nanoparticles. As shown, the spectrum exhibits a broad band at approximately 3452 cm−1 and a peak at 1627 cm−1, which are attributed to the stretching and bending vibrations of hydroxyl (OH) groups, respectively.41 Furthermore, the absorption bands in the 580–450 cm−1 range are attributed to the metal–oxide (M–O) stretching vibrations of Co–O and Fe–O.42 The FT-IR spectrum of the CoFe2O4-SiO2 nanoparticles is presented in Fig. 2b. Following the reaction with TEOS, a new peak emerged at 1074 cm−1, which is assigned to the Si–O–Si stretching vibration, confirming the successful coating/modification. The spectrum of Fig. 2c is related to the Cs-DBP-HBA compound. As observed, the peaks at approximately 1379 and 1074 cm−1 are assigned to the C–O–C stretching vibrations.43 Furthermore, the FT-IR spectrum of Cs-DBP-HBA exhibited a peak at 1622 cm−1, corresponding to the C Created by potrace 1.16, written by Peter Selinger 2001-2019 N stretching vibration. This peak is attributed to the formation of a Schiff base between the residual free amino groups of chitosan and 4-hydroxybenzaldehyde. The FT-IR spectrum of the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite is presented in Fig. 2d. A broad band centered at 3414 cm−1 is assigned to various OH stretching vibrations, whereas the peaks observed at 1629, 1384, 1087, 586, and 460 cm−1 are attributed to the imine group C Created by potrace 1.16, written by Peter Selinger 2001-2019 N, C–O–C, Si–O–Si, Co–O, and Fe–O stretching modes, respectively.

Fig. 2. FT-IR spectra of (a) CoFe2O4, (b) CoFe2O4-SiO2, (c) Cs-DBP-HBA, (d) Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite.

Fig. 2

Open in a new tab

3.2. XRD analysis

The XRD pattern of the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite is presented in Fig. 3. The diffraction peaks observed at 2θ = 30.2° (220), 35.5° (311), 43° (400), 53.7° (422), 57.2° (511), and 62.8° (440) are characteristic of the CoFe2O4 spinel phase, which is in good agreement with previously reported values for cobalt ferrite nanoparticles.44 Additionally, the peak at 2θ = 20.5° is assigned to the chitosan structure.45 The average crystallite size of the Cs-HBA-CoFe2O4-SiO2 nanocomposite was estimated using the Debye–Scherrer eqn (3):

3.2. 3

where D is the average size, λ is the X-ray source wavelength (1.54 Å), β is the full width at half maximum (FWHM) of the diffraction peak and θ is the Bragg's angle. Based on the Debye–Scherrer formula, the crystallite size of the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite was determined to be 31 nm.

Fig. 3. XRD pattern of the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite.

Fig. 3

Open in a new tab

3.3. FESEM and EDS analysis

Field Emission Scanning Electron Microscopy (FESEM) was utilized to investigate the morphology and particle size of the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite. As illustrated in Fig. 4, the nanocomposite displays a spherical morphology with relatively uniform size distribution, having an average particle diameter of 41.50 nm. Furthermore, the chemical composition of the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite was analyzed by Energy-dispersive X-ray spectroscopy (EDS). Fig. 5 presents the EDS spectrum of the nanocomposite. The spectrum verifies the presence of the C, N, O, Si, Co, and Fe elements. Based on the EDS results, the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite contains Fe, Co, Si, O, C, and N, with atomic percentages of 14.18%, 8.94%, 17.52%, 47.40%, 8.88%, and 3.08%, respectively.

Fig. 4. FESEM image of Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite.

Fig. 4

Open in a new tab

Fig. 5. EDS patterns of Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite.

Fig. 5

Open in a new tab

3.4. Magnetization analysis (VSM)

The magnetic behavior of CoFe2O4, CoFe2O4-SiO2, and Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite was evaluated under an applied magnetic field ranging from −10 000 to 10 000 Oe. Fig. 6 illustrates the room-temperature magnetization curves of these samples. A successive decrease in saturation magnetization (Ms) was observed, transitioning from pure CoFe2O4 to the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite (50, 23, and 8 emu g−1, respectively). This trend confirms the successful surface coating of CoFe2O4 nanoparticles with silica, chitosan, and 4-hydroxybenzaldehyde.

Fig. 6. Magnetic hysteresis loops of (a) CoFe2O4, (b) CoFe2O4-SiO2 and (c) Cs-HBA-CoFe2O4-SiO2 nanocomposite.

Fig. 6

Open in a new tab

3.5. Brunauere–Emmette–Teller (BET)

The Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite exhibited a Type IV nitrogen adsorption–desorption isotherm, characteristic of mesoporous materials, coupled with a Type H3 hysteresis loop (Fig. S1), indicating the presence of slit-shaped pores. These features collectively confirm the mesoporous nature of the nanocomposite.46 The specific surface area, calculated using the BET method, was found to be 14.42 m2 g−1, with a corresponding Langmuir surface area of 15.74 m2 g−1 (Table S1). Further analysis of the pore structure using the BJH method revealed a bimodal pore size distribution (Fig. S2). A prominent peak is observed at approximately 1.88 nm, situated at the boundary between micropores and small mesopores. Considering the inherent tendency of the BJH model to slightly underestimate pore diameters near this transition, this peak predominantly represents small mesopores. This is further supported by a broader mesoporous distribution evident in the 10–20 nm range, contributing to a mean pore diameter of 7.17 nm derived from BET analysis. This hierarchical porosity is highly advantageous for the adsorption of Methylene Blue (MB), as the larger mesopores facilitate rapid mass transfer and diffusion of the dye molecules into the internal framework, while the smaller pores provide a high specific surface area for effective adsorption sites.

3.6. TGA analysis

The thermal stability of the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite was investigated via thermogravimetric analysis (TGA). The corresponding TGA and Differential Thermal Analysis (DTA) profiles are illustrated in Fig. S3. The analysis revealed three distinct degradation stages between 25 and 600 °C. Initially, a mass reduction of 9.8% was recorded from 25 to 223 °C, which is likely due to the evaporation of adsorbed moisture.47 This was followed by a significant weight loss of 33.3% in the 228–350 °C range, stemming from the breakdown of oxygen-containing functional groups.48 Subsequently, between 350 and 550 °C, a further 23.8% mass loss occurred, attributed to the decomposition of the carbon framework.49 Finally, a residual mass of 33.1% was obtained.

3.7. Sorption studies of selected dye

3.7.1. Effect of adsorbent dosage

The impact of adsorbent dosage on methylene blue (MB) removal was investigated by varying the sorbent amount from 10 to 80 mg in a 10 mL solution of 100 mg L−1 dye at 25 °C, with a contact time of 30 minutes. The relationship between adsorbent dosage and dye removal efficiency is depicted in Fig. 7. It was observed that increasing the dosage significantly enhanced the MB removal percentage, which rose from 74.1% to 98.4% as the amount of Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite increased. This improvement is ascribed to the augmented surface area and the higher availability of active adsorption sites provided by the increased dosage. Based on these findings, an optimal dose of 40 mg was selected for subsequent studies.

Fig. 7. Effect of adsorbent dose on removal of MB dye by Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite (25 °C, pH = 7, 25 min, initial dye concentrations 100 mg L−1).

Fig. 7

Open in a new tab

3.7.2. Effect of initial dye concentration

The effect of initial dye concentration on the adsorption of MB onto the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite was evaluated at room temperature, with concentrations ranging from 20 to 150 mg L−1 while keeping other experimental parameters constant. As illustrated in Fig. 8, the removal efficiency decreased from approximately 91.6% to 77.9% as the initial dye concentration increased. This trend suggests that at higher concentrations, the number of dye molecules exceeds the available active sites on the nanocomposite surface, thereby hindering further adsorption. Consequently, an initial concentration of 100 mg L−1 was selected as the optimal value for subsequent adsorption experiments.

Fig. 8. Effect of initial dye concentration on removal of MB dye by Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite (25 °C, pH = 7, 25 min, adsorbent dose 40 mg).

Fig. 8

Open in a new tab

3.7.3. Effect of contact time

Contact time is a critical factor in dye adsorption efficiency. In this study, the adsorption of MB onto the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite was evaluated at room temperature. Experiments were conducted with a fixed adsorbent dosage of 40 mg and an initial MB concentration of 100 mg L−1, while varying the contact time from 10 to 60 minutes. As depicted in Fig. 9, the nanocomposite achieved complete dye removal within 30 minutes; consequently, this duration was identified as the optimum contact time for the process.

Fig. 9. Effect of contact time on removal of MB dye by Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite (25 °C, pH = 7, initial dye concentrations 100 mg L−1, adsorbent dose 40 mg).

Fig. 9

Open in a new tab

3.7.4. Effect of initial pH solution

Here, we investigated the effect of varying the initial pH (3 to 11) on the uptake of MB by the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite (Fig. 10). The pH was adjusted using 0.01 N HCl or NaOH solutions. This study revealed a U-shaped pH dependency, where removal performance was significantly higher in both acidic and alkaline media, with a notable decline at neutral pH. This trend reflects the synergistic interplay between pH-dependent electrostatic forces and pH-independent non-electrostatic interactions. In alkaline conditions, the deprotonation of surface functional groups results in a net negative surface charge, facilitating strong electrostatic attraction toward the cationic MB molecules. At neutral pH, the system approaches the point of zero charge, where the effective surface charge is minimized, leading to a reduction in electrostatic driving forces. Conversely, in acidic media, although the protonation of surface groups generates electrostatic repulsion against the cationic dye, the high adsorption efficiency is maintained by dominant non-electrostatic, physisorption-like interactions. Specifically, pi–pi stacking between the aromatic rings of MB and the 4-hydroxybenzaldehyde units, alongside dispersion forces, compensate for the electrostatic repulsion. Therefore, the U-shaped profile signifies that the nanocomposite utilizes multifaceted physical–chemical interactions: electrostatic attraction at high pH and pi–pi mediated interactions at low pH, ensuring high versatility across a wide pH range.50,51

Fig. 10. Effect of initial pH on removal of MB dye by Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite (25 °C, 30 min, initial dye concentrations 100 mg L−1, adsorbent dose 40 mg).

Fig. 10

Open in a new tab

3.8. Adsorption isotherms

Adsorption isotherms constitute a fundamental parameter in adsorption studies, offering critical insights into the underlying adsorption mechanisms and the nature of interactions between dye molecules and the adsorbent surface. In this study, the adsorption characteristics of methylene blue (MB) onto the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite were investigated through the application of Langmuir, Freundlich and Temkin isotherm models to extract the relevant thermodynamic parameters. The Langmuir model, which assumes the formation of a monolayer on the adsorbent surface was employed.46 The linear representation of the Langmuir isotherm is expressed in eqn (4):

3.8. 4

In the aforementioned equation, Ce and qe (mg g−1) correspond to the equilibrium concentration of the dye solution (mg L−1) and the amount of dye adsorbed, respectively. Fig. 11 showed that the linear plot for the Langmuir model was obtained at room temperature. qm characterizes the maximum monolayer adsorption capacity, whereas KL represents the Langmuir affinity constant (mg L−1). As shown in Table 1, the maximum monolayer adsorption capacity (qm) determined via the Langmuir model was 39.37 mg g−1, with a corresponding regression coefficient (R2) of 0.9729. To further elucidate the nature of the adsorption process, the dimensionless separation factor (RL) was evaluated according to eqn (5):

3.8. 5

where KL denotes the Langmuir equilibrium constant (L mg−1) and C0 represents the initial concentration of the dye (mg L−1). The RL parameter serves as a critical indicator for classifying the adsorption isotherm into distinct regimes: RL > 1 (unfavorable), RL = 1 (linear), 0 < RL < 1 (favorable), and RL = 0 (irreversible). As summarized in Table 1, the calculated RL values for the methylene blue adsorption onto the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite were situated within the range of 0 < RL < 1. This confirms that the adsorption process is highly favorable, suggesting a strong affinity between the methylene blue molecules and the active sites of the synthesized nanocomposite.

Fig. 11. Langmuir plot for the adsorption of MB onto the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite.

Fig. 11

Open in a new tab

Table 1. Langmuir, Freundlich and Temkin isotherms parameters and correlation coefficients for the adsorption of MB onto HBA-CoFe2O4-SiO2 nanocomposite.

Langmuir isotherm parameters Freundlich isotherm parameters Temkin isotherm parameters
q m (mg g−1) K L (L mg−1) R L R 2 K F (L mg−1) n R 2 A (L g−1) B b (J mol−1) R 2
39.37 0.092 0.098 0.9729 21.37 1.52 0.9636 0.89 8.63 280.64 0.9669
Open in a new tab

To account for the potential heterogeneity of the adsorption sites on the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite, the Freundlich isotherm model was applied. This model assumes that adsorption occurs on a surface with energetically non-equivalent sites. The linear expression of the Freundlich equation is given by eqn (6):

3.8. 6

where KF represents the Freundlich adsorption capacity and 1/n serves as an indicator of adsorption intensity. The parameter 1/n is a crucial metric for characterizing the adsorption nature: 1/n = 0 signifies irreversible adsorption, 0 < 1/n < 1 denotes favorable adsorption, and 1/n > 1 indicates unfavorable adsorption.

Based on the linear regression of ln qeversus ln Ce at 25 °C (Fig. 12), the Freundlich parameters were determined. As summarized in Table 1, the obtained n values were significantly greater than unity (n > 1), which corresponds to a 1/n value within the favorable range (0 < 1/n < 1). This, coupled with a high regression coefficient (R2 = 0.9636), confirms that the adsorption of methylene blue onto the adsorbent surface is a favorable process occurring on a heterogeneous surface.

Fig. 12. Freundlich plot for the adsorption of MB onto the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite.

Fig. 12

Open in a new tab

To gain deeper insights into the energetic aspects of the adsorption process, the Temkin isotherm model was employed. Unlike other models, the Temkin isotherm explicitly accounts for adsorbate–adsorbent interactions by assuming that the heat of adsorption decreases linearly with increased surface coverage due to adsorbent–adsorbate interactions.46 The mathematical representation of the Temkin model (7) is expressed as:

qe = B ln A + B ln Ce 7

where B is a constant related to the heat of adsorption, defined by B = RT/b (eqn (7)). Here, R is the universal gas constant (8.314 J mol−1 K−1), T represents the absolute temperature (K), b is the Temkin constant related to the heat of adsorption (J mol−1), and A is the equilibrium binding constant (L g−1). The parameters A and b were derived from the linear regression of qeversus ln Ce (Fig. 13). As summarized in Table 1, the calculated Temkin constants provide critical evidence regarding the adsorption mechanism. Specifically, the results suggest that the adsorption process is characterized by physisorption, involving weak non-covalent interactions (such as hydrogen bonding or pi–pi stacking) rather than chemisorption, as evidenced by the calculated heat of adsorption.

Fig. 13. Temkin plot for the adsorption of MB onto the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite.

Fig. 13

Open in a new tab

3.9. Kinetic analysis of adsorption

To elucidate the adsorption kinetics and uncover the underlying rate-controlling mechanisms of the drug uptake process, the experimental data were rigorously analyzed using both pseudo-first-order (PFO) (8) and pseudo-second-order (PSO) (9) kinetic models.52 The mathematical descriptions for these models are expressed in their linearized forms as follows:

3.9. 8
3.9. 9

where qe and qt (mg g−1) denote the adsorption capacity at equilibrium and at a specific time t, respectively, while k1 and k2 (min−1) represent the respective rate constants. The kinetic profiles for methylene blue adsorption onto the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite are illustrated in Fig. 14, and the calculated parameters are summarized in Table 2. While both the PFO and PSO models provided satisfactory fits, the PFO model yielded a superior coefficient of determination (R2 = 0.9883) compared to the PSO model (R2 = 0.9864). This kinetic behavior indicates that the adsorption rate is primarily governed by physisorption-mediated processes. Specifically, the fit to the PFO model suggests that the adsorption rate is proportional to the number of vacant sites on the adsorbent surface, reinforcing the role of physical interactions such as electrostatic attraction in the overall uptake mechanism.

Fig. 14. Pseudo-first-order (a) and pseudo-second-order (b) model for the removal kinetics of MB Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite.

Fig. 14

Open in a new tab

Table 2. Kinetic parameters for the adsorption of MB onto Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite.

Pseudo-first-order Pseudo-second-order
q e (mg g−1) K 1 (×10−3) (min−1) R 2 q e (mg g−1) K 2 (×10−3) (min−1) R 2
12.58 52.7 0.9883 26.45 6.9 0.9864
Open in a new tab

3.10. Thermodynamic analysis of adsorption

To gain deeper insights into the thermodynamic feasibility and the nature of the adsorption process of methylene blue (MB) onto the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite, thermodynamic parameters—including the standard Gibbs free energy change (ΔG°), standard enthalpy change (ΔH°), and standard entropy change (ΔS°)—were calculated.52 These parameters provide critical information regarding the energy requirements and the spontaneity of the adsorption system. The thermodynamic equilibrium constant (KC) at various temperatures was utilized to determine these parameters using the van't Hoff eqn (10) and the fundamental Gibbs–Helmholtz relation (11):

3.10. 10
ΔG° = ΔH° − TΔS° 11

In these expressions, T represents the absolute solution temperature (K) and R denotes the universal gas constant (8.314 J mol−1 K−1). The values ofΔH° and ΔS° were determined from the slope and the intercept of the linear plot of ln KCversus 1/T (Fig. 15). The calculated thermodynamic parameters are summarized in Table 3. The sign and magnitude of these values reveal the nature of the interaction at the solid–liquid interface: (1) the obtained positive value of ΔH° indicates that the adsorption of MB onto the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite is an endothermic process. This suggests that an increase in temperature facilitates the adsorption capacity, likely due to the increased mobility of the adsorbate molecules or the availability of more active sites on the nanocomposite surface at higher temperatures. (2) The positive value of ΔS° reflects an increase in the randomness and disorder at the solid–solution interface during the adsorption process. This phenomenon often occurs as the adsorbed molecules displace solvent molecules (water) from the surface, leading to an increase in the degrees of freedom of the system. (3) The negative values of ΔG° across the studied temperature range confirm that the adsorption of MB onto the nanocomposite is a spontaneous and thermodynamically favorable process under the experimental conditions. Furthermore, the decrease in ΔG° values with increasing temperature suggests that the spontaneity of the adsorption process is enhanced at higher temperatures. To further investigate the nature of the adsorption, the isosteric heat of adsorption (Qst) was calculated using the Clausius–Clapeyron eqn (12):46

3.10. 12

Fig. 15. Thermodynamic plot for removal of MB on Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite.

Fig. 15

Open in a new tab

Table 3. Thermodynamic parameters for the adsorption of MB on Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite.

Adsorbent Adsorbate ΔH° (kJ mol−1) ΔS° (kJ mol−1) ΔG° (kJ mol−1)
Cs-DBP-HBA-CoFe2O4-SiO2 MB 41.154 0.188 293 K 303K 313 K 323 K
−13.93 −15.81 −17.69 −19.57
Open in a new tab

The isotherm data at various temperatures were used to determine the equilibrium concentration (Ce) at constant amounts of MB (Table S2). The value of Qst was obtained from the slope of a plot of ln Ceversus 1/T (Fig. S4). The calculated Qst value of 22.66 kJ mol−1 indicates that the adsorption process is physisorption in nature. This result, combined with the observed increase in qm and KL with temperature, provides conclusive evidence that the adsorption of MB onto the synthesized nanocomposite is an endothermic process.

3.11. Adsorption mechanism

Fig. 16 illustrates the proposed mechanism for the adsorption of Methylene Blue (MB) onto the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite. As depicted, the adsorption process is governed by a synergistic combination of multiple interaction pathways. Firstly, pi–pi stacking interactions occur between the aromatic rings of the MB molecule and the conjugated structure of the 4-hydroxybenzaldehyde (HBA) moiety. A key feature of the adsorption mechanism is the strong electrostatic interaction, particularly between the negatively charged surface functional groups of the nanocomposite and the positively charged MB cations (specifically O⋯N+ interactions), which provide significant stabilization. In contrast, other observed contacts, such as S⋯H–CH and N⋯H–CH, are predominantly dispersive in nature and thus represent weaker intermolecular forces. Additionally, the role of hydrogen bonding should not be overlooked; the abundant amine (–NH2) and hydroxyl (–OH) groups on the chitosan backbone and HBA shell provide active sites that interact with the electronegative atoms within the MB structure. Collectively, the energy profile of these multifaceted interactions, ranging from strong electrostatic attractions to weaker dispersive forces, is consistent with the calculated thermodynamic parameters, confirming that the overall adsorption is predominantly a physical–chemical process governed by non-covalent interactions.

Fig. 16. Mechanism of MB adsorption on Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite.

Fig. 16

Open in a new tab

3.12. Reusability studies

To evaluate the reusability of the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite, 40 mg of the adsorbent was added to 25 mL of a 100 mg L−1 dye solution and stirred at 200 rpm for 30 min at 298 K. Following filtration, the dye-loaded nanocomposite was treated with 0.1 M HCl for desorption. The Fig. 17 shows that after four cycles, the dye removal percentage decreased slightly and was still 66%.

Fig. 17. Regeneration studies for the adsorption–desorption of MB onto Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite (200 rpm, 30 min, initial dye concentrations 100 mg L−1, adsorbent dose 40 mg).

Fig. 17

Open in a new tab

3.13. Comparison with other reported adsorbents

The adsorption capacity of the Cs-DBP-HBA-CoFe2O4-SiO2 nanocomposite for MB removal was compared with other adsorbents reported in the literature (Table 4). As shown in Table 4, the composite shows a reasonable adsorption capacity compared with many previously reported adsorbents.

Table 4. Comparison of the adsorption capacity of present system with other reported systems.

Adsorbents Dye q m (mg g−1) References
Polyaniline@graphene oxide MB 14.2 53
Zeolite MB 21.4 54
Polystyrene@silica nanocomposite MB 23.1 55
Magnetic rGO/AK/Fe3O4 nanocomposite MB 39.8 56
Activated lignin–chitosan composite extrudates MB 36.2 57
MgFe2O4/reduced graphene oxide MB 21 58
Polyaniline/reduced graphene oxide MB 19.2 59
CZC MB 24.5 60
ZnO-g-C3N4@(CMCH/ALG-g-PAA) MB 24.3 61
Carboxymethyl cellulose grafted polyacrylamide/carbon black nanocomposite hydrogel MB 27.32 62
Cs-DBP-HBA-CoFe2O4-SiO2 MB 39.37 Present study
Open in a new tab

4. Conclusion

In this study, a novel magnetic chitosan/1,3-dibromopropane/4-hydroxybenzaldehyde/CoFe2O4/SiO2 (Cs-DBP-HBA-CoFe2O4-SiO2) nanocomposite was successfully synthesized and characterized using a range of advanced analytical techniques, including FT-IR, XRD, FE-SEM, VSM, EDS, TGA, and BET. The synthesized nanocomposite demonstrated excellent performance as an efficient adsorbent for the removal of methylene blue (MB) from aqueous solutions. Batch adsorption experiments determined the optimal conditions to be an adsorbent dosage of 40 mg L−1, initial dye concentration of 100 mg L−1, pH 3, and a contact time of 30 min. The adsorption process was found to be highly favorable, occurring on a heterogeneous surface, as evidenced by isotherm modeling. A comparative kinetic assessment confirmed that the pseudo-first-order (PFO) model provided the best fit to the experimental data, indicating that the rate-limiting step is predominantly governed by a physisorption mechanism. This process is driven by non-covalent interactions, specifically hydrogen bonding and pi–pi stacking, rather than chemical bond formation. According to the Langmuir analysis, the maximum adsorption capacity (qm) of the adsorbent for MB was obtained to be 39.37 mg g−1. Thermodynamic studies revealed that the adsorption of MB onto the nanocomposite is a spontaneous and endothermic process.

Conflicts of interest

There are no conflicts to declare.

Supplementary Material

RA-OLF-D6RA08198C-s001

Data availability

All the data obtained during experimentation is given in the manuscript.

Supplementary information (SI) is available. See DOI: https://doi.org/10.1039/d6ra08198c.

References

  1. Dhamorikar R. S. Lade V. G. Kewalramani P. V. Bindwal A. B. Review on integrated advanced oxidation processes for water and wastewater treatment. J. Ind. Eng. Chem. 2024;138:104–122. doi: 10.1016/j.jiec.2024.04.037. [DOI] [Google Scholar]
  2. Merchant A. I. Vakili A. H. kocaman A. Abu Amr S. S. New advancement of advanced oxidation processes for the treatment of Petroleum wastewater. Desalination Water Treat. 2024;319:100565. doi: 10.1016/j.dwt.2024.100565. [DOI] [Google Scholar]
  3. Kesari K. K. Soni R. Jamal Q. M. S. Tripathi P. Lal J. A. Jha N. K. Siddiqui M. H. Kumar P. Tripathi V. Ruokolainen J. Wastewater Treatment and Reuse: a Review of its Applications and Health Implications. Water, Air, Soil Pollut. 2021;232:208. doi: 10.1007/s11270-021-05154-8. [DOI] [Google Scholar]
  4. Picinini-Zambelli J. Letícia Hilário Garcia A. Da Silva J. Emerging pollutants in the aquatic environments: A review of genotoxic impacts. Mutat. Res. 2025;795:108519. doi: 10.1016/j.mrrev.2024.108519. [DOI] [PubMed] [Google Scholar]
  5. Yagub M. T. Sen T. K. Afroze S. Ang H. M. Dye and Its Removal from Aqueous Solution by Adsorption: A Review. Adv. Colloid Interface Sci. 2014;209:172–184. doi: 10.1016/j.cis.2014.04.002. https://dx.doi.org/10.1016/j.cis.2014.04.0026 [DOI] [PubMed] [Google Scholar]
  6. Waheed A. Baig N. Ullah N. Falath W. Removal of hazardous dyes, toxic metal ions and organic pollutants from wastewater by using porous hyper-cross-linked polymeric materials: A review of recent advances. J. Environ. Manage. 2021;287:112360. doi: 10.1016/j.jenvman.2021.112360. [DOI] [PubMed] [Google Scholar]
  7. Bilal M. Ihsanullah I. Ul Hassan Shah M. Reddy A. V. B. Aminabhavi T. M. Recent advances in the removal of dyes from wastewater using low-cost adsorbents. J. Environ. Manage. 2022;321:115981. doi: 10.1016/j.jenvman.2022.115981. [DOI] [PubMed] [Google Scholar]
  8. Al-Tohamy R. Ali S. S. Li F. Okasha K. M. Mahmoud Y. A. G. Elsamahy T. Jiao H. Fu Y. Sun J. A critical review on the treatment of dye-containing wastewater: Ecotoxicological and health concerns of textile dyes and possible remediation approaches for environmental safety. Ecotoxicol. Environ. Saf. 2022;231:113160. doi: 10.1016/j.ecoenv.2021.113160. [DOI] [PubMed] [Google Scholar]
  9. Sağlam S. Türk F. N. Arslanoğlu H. Use and applications of metal-organic frameworks (MOF) in dye adsorption: Review. J. Environ. Chem. Eng. 2023;11:110568. doi: 10.1016/j.jece.2023.110568. [DOI] [Google Scholar]
  10. Shang W. J. Wang X. L. Yu Y. X. Theoretical calculation on the membrane potential of charged porous membranes in 1-1, 1-2, 2-1 and 2-2 electrolyte solutions. J. Membr. Sci. 2006;285:362–375. doi: 10.1016/j.memsci.2006.09.005. [DOI] [Google Scholar]
  11. Zhang Y. N. Yu Y. X. Adsorptive removal of Cr3+, Cu2+, and Ni2+ ions by magnetic Fe3O4@alkali-treated coal fly ash. Desalination Water Treat. 2018;123:277–287. doi: 10.5004/dwt.2018.22778. [DOI] [Google Scholar]
  12. Islam Md. M. Aidid A. R. Mohshin J. N. Mondal H. Ganguli S. Chakraborty A. K. A critical review on textile dye-containing wastewater: Ecotoxicity, health risks, and remediation strategies for environmental safety. Cleaner Chem. Eng. 2025;11:100165. doi: 10.1016/j.clce.2025.100165. [DOI] [Google Scholar]
  13. Dutta S. ramha Gupta B. Srivastava S. Gupta A. K. Recent advances on the removal of dyes from wastewater using various adsorbents: A critical review. Mater. Adv. 2021;2:4497–4531. doi: 10.1039/D1MA00354B. https://dx.doi.org/10.1039/d1ma00354b [DOI] [Google Scholar]
  14. Roslan N. N. Lau H. L. H. Suhaimi N. A. A. Shahri N. N. M. Verinda S. B. Nur M. Lim J. W. Usman A. Recent Advances in Advanced Oxidation Processes for Degrading Pharmaceuticals in Wastewater—A Review. Catalysts. 2024;14(3):189. doi: 10.3390/catal14030189. [DOI] [Google Scholar]
  15. Agarwala R. Mulky L. Adsorption of Dyes from Wastewater: A Comprehensive Review. ChemBioEng Rev. 2023;10:326–335. doi: 10.1002/cben.202200011. [DOI] [Google Scholar]
  16. Khader E. H. Muslim S. A. Cata Saady N. M. Ali N. S. Salih I. K. Mohammed T. J. Albayati T. M. Zendehboudi S. Recent advances in photocatalytic advanced oxidation processes for organic compound degradation: A review. Desalination Water Treat. 2024;318:100384. doi: 10.1016/j.dwt.2024.100384. [DOI] [Google Scholar]
  17. Chen Y. Lin Y. C. Ho S. H. Zhou Y. Ren N. Highly efficient adsorption of dyes by biochar derived from pigments-extracted macroalgae pyrolyzed at different temperature. Bioresour. Technol. 2018;259:104–110. doi: 10.1016/j.biortech.2018.02.094. [DOI] [PubMed] [Google Scholar]
  18. Swamy K. R. Shyamala G. Gurugubelli T. R. Ravindran G. Bathula B. Recent advancements of wastewater treatment by photocatalysis: A comprehensive review. iScience. 2026;29:116088. doi: 10.1016/j.isci.2026.116088. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Song J. Zhu L. Yu S. Li G. Wang D. The synergistic effect of adsorption and Fenton oxidation for organic pollutants in water remediation: an overview. RSC Adv. 2024;14(45):33489–33511. doi: 10.1039/D4RA03050H. https://dx.doi.org/10.1039/d4ra03050h [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Tsukada A. Konno H. Simultaneous removal of various organic dyes from aqueous solutions using a UiO-67-type metal–organic framework. Colloids Surf., A. 2024;686:133330. doi: 10.1016/j.colsurfa.2024.133330. [DOI] [Google Scholar]
  21. Kayani K. F. Bimetallic metal–organic frameworks (BMOFs) for dye removal: a review. RSC Adv. 2024;14(43):31777–31796. doi: 10.1039/D4RA06626J. https://dx.doi.org/10.1039/d4ra06626j [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Islam A. Ul Haq Khan Z. Islam M. El-Sabban H. A. Kang J. H. Advanced nanocomposite materials for efficient adsorptive remediation of pharmaceutical pollutants in aquatic systems. J. Mol. Liq. 2026;442:129082. doi: 10.1016/j.molliq.2025.129082. [DOI] [Google Scholar]
  23. Hussein E. B. Rasheed F. A. Mohammed A. S. Kayani K. F. Emerging nanotechnology approaches for sustainable water treatment and heavy metals removal: a comprehensive review. RSC Adv. 2025;15(48):41061–41107. doi: 10.1039/D5RA06914A. https://dx.doi.org/10.1039/d5ra06914a [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Al-Ghouti M. A. Ashfaq M. Y. Khan M. Al Disi Z. Da'na D. A. Shoshaa R. State-of-the-art adsorption and adsorptive filtration based technologies for the removal of trace elements: A critical review. Sci. Total Environ. 2023;895:164854. doi: 10.1016/j.scitotenv.2023.164854. [DOI] [PubMed] [Google Scholar]
  25. Kassa A. Engida A. Minbale Endaye, Eco-friendly adsorbents for industrial dye removal: A comprehensive review of low-cost alternatives. Desalination Water Treat. 2025;323:101362. doi: 10.1016/j.dwt.2025.101362. [DOI] [Google Scholar]
  26. Pandey G. Singh S. Hitkari G. Synthesis and characterization of polyvinyl pyrrolidone (PVP)-coated Fe3O4 nanoparticles by chemical co-precipitation method and removal of Congo red dye by adsorption process. Int. Nano Lett. 2018;8:111–121. doi: 10.1007/s40089-018-0234-6. [DOI] [Google Scholar]
  27. Saadat A. Banaei A. Sattarifar M. Pargolghasemi P. Preparation 2-hydroxy-1-naphthaldehyde cross-linked Fe3O4@chitosan-polyacrylamide nanocomposite for removal of everzol black from aqueous solutions. Sci. Rep. 2023;13:10618. doi: 10.1038/s41598-023-37243-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Saadat A. Banaei A. Javadi R. Pargolghasemi P. Preparation magnetic graphene oxide/diethylenetriamine composite for removal of methylene blue from aqueous solutions. Sci. Rep. 2024;14:15457. doi: 10.1038/s41598-024-65628-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Deivasigamani P. Gajendiran V. Chitra B. Kumar P. S. Balasubramanian N. Sundararaman S. Dhananjeyan V. Subramani L. Jagadeesan A. K. Sivamani S. Chellappa R. Rangasamy G. Magnetic Nanoparticles: Synthesis, characterization and application based on environmental Perspective. Results Chem. 2025;14:102023. doi: 10.1016/j.rechem.2025.102023. [DOI] [Google Scholar]
  30. Lu N. Sun Y. Li Y. Liu Z. Wang N. Meng T. Luo Y. A Review on the Application of Magnetic Nanomaterials for Environmental and Ecological Remediation. Toxics. 2025;13(10):814. doi: 10.3390/toxics13100814. [DOI] [PMC free article] [PubMed] [Google Scholar]
  31. Hasana I. Bhatiaa D. Waliaa S. Singha P. Removal of Malachite Green by Polyacrylamide-g-Chitosan γ-Fe2O3 nanocomposite-An application of Central Composite Design. Groundwater Sustainable Dev. 2020;11:100378. doi: 10.1016/j.gsd.2020.100378. [DOI] [Google Scholar]
  32. Mulushewa Z. Dinbore W. T. Ayele Y. Removal of methylene blue from textile waste water using kaolin and zeolite-x synthesized from Ethiopian kaolin. Environ. Anal. Health Toxicol. 2021;36:e2021007. doi: 10.5620/eaht.2021007. [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Rafie S. F. Abu-Zahra N. Sillanpaa M. A comprehensive review of spinel ferrites and their magnetic composites as highly efficient adsorbents of rare earth elements. Emerging Contam. 2025;11:100429. doi: 10.1016/j.emcon.2024.100429. [DOI] [Google Scholar]
  34. Salih S. J. Tahseen Z. S. Spinel ferrite nanoparticles in environmental remediation: Adsorption, catalysis, and sustainability perspectives. Next Sustainability. 2026;7:100240. doi: 10.1016/j.nxsust.2025.100240. [DOI] [Google Scholar]
  35. Zhang Y. Zhao M. Cheng Q. Wang C. Li H. Han X. Fan Z. Su G. Pan D. Li Zh. Research progress of adsorption and removal of heavy metals by chitosan and its derivatives: A review. Chemosphere. 2021;279:130927. doi: 10.1016/j.chemosphere.2021.130927. [DOI] [PubMed] [Google Scholar]
  36. Atangana E. Ajiboye T. O. Mafolasire A. A. Ghosh S. Hakeem B. Adsorption of Organic Pollutants from Wastewater Using Chitosan-Based Adsorbents. Polymers. 2025;17:502. doi: 10.3390/polym17040502. [DOI] [PMC free article] [PubMed] [Google Scholar]
  37. Dambuza A. Mokolokolo P. P. Makhatha M. E. Sibeko M. A. Chitosan-Based Materials as Effective Materials to Remove Pollutants. Polymers. 2025;17(18):2447. doi: 10.3390/polym17182447. [DOI] [PMC free article] [PubMed] [Google Scholar]
  38. Begum S. Yuhana N. Y. Md Saleh N. Kamarudin N. H. N. Sulong A. B. Review of chitosan composite as a heavy metal adsorbent: Material preparation and properties. Carbohydr. Polym. 2021;259:117613. doi: 10.1016/j.carbpol.2021.117613. [DOI] [PubMed] [Google Scholar]
  39. Fan L. Zhang Y. Luo C. Lu F. Qiu H. Sun M. Synthesis and characterization of magnetic b-cyclodextrin-chitosan nanoparticles as nano-adsorbents for removal of methyl blue. Int. J. Biol. Macromol. 2012;50:444e450. doi: 10.1016/j.ijbiomac.2011.12.016. [DOI] [PubMed] [Google Scholar]
  40. Zhou Z. Lin S. Yue T. Ch Lee T. Adsorption of food dyes from aqueous solution by glutaraldehyde cross-linked magnetic chitosan nanoparticles. J. Food Eng. 2014;126:133e141. doi: 10.1016/j.jfoodeng.2013.11.014. [DOI] [Google Scholar]
  41. Rashid Z. Naeimi H. Zarnani A. H. Zarnani A. H. Fast and highly efficient purification of histidine-tagged recombinant proteins by Ni-decorated MnFe2O4@SiO2@NH2@2AB as novel and efficient affinity adsorbent magnetic nanoparticles. RSC Adv. 2016;6:36840–36848. doi: 10.1039/C5RA25949E. https://dx.doi.org/10.1039/c5ra25949e [DOI] [Google Scholar]
  42. Zinatloo-Ajabshir S. Ghasemian N. Salavati-Niasari M. Green synthesis of Ln2Zr2O7 (Ln = Nd, Pr) ceramic nanostructures using extract of green tea via a facile route and their efficient application on propane-selective catalytic reduction of NOx process. Ceram. Int. 2020;46:66. doi: 10.1016/j.ceramint.2019.08.231. [DOI] [Google Scholar]
  43. Cinar S. Kaynar U. H. Aydemir T. Kaynar S. C. Ayvacikli M. An efficient removal of RB5 from aqueous solution by adsorption onto nano-ZnO/Chitosan composite beads. Int. J. Biol. Macromol. 2017;96:459. doi: 10.1016/j.ijbiomac.2016.12.021. [DOI] [PubMed] [Google Scholar]
  44. Guchhait S. Aireddy H. Das A. K. The emergence of high room temperature in-plane and out-of-plane magnetostriction in polycrystalline CoFe2O4 film. Sci. Rep. 2021;11:22890. doi: 10.1038/s41598-021-02421-w. [DOI] [PMC free article] [PubMed] [Google Scholar]
  45. Hoque M. A. Ahmed M. R. Rahman G. T. Rahman M. T. Islam M. A. Khan M. A. Hossain M. K. Fabrication and Comparative Study of Magnetic Fe and α-Fe2O3 Nanoparticles Dispersed Hybrid Polymer (PVA+Chitosan) Novel Nanocomposite Film. Results Phys. 2018;10:434–443. doi: 10.1016/j.rinp.2018.06.010. [DOI] [Google Scholar]
  46. 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. doi: 10.1016/j.jhazmat.2020.122383. [DOI] [PubMed] [Google Scholar]
  47. Tanhaei B. Ayati A. Lahtinen M. Sillanpaa M. Preparation and characterization of a novel chitosan/Al2O3/magnetite nanoparticles composite adsorbent for kinetic, thermodynamic and isotherm studies of Methyl Orange adsorption. Chem. Eng. J. 2015;259:1–10. doi: 10.1016/j.cej.2014.07.109. [DOI] [Google Scholar]
  48. Travlou N. A. Kyzas G. Z. Lazaridis N. K. Deliyanni E. A. Functionalization of graphite oxide with magnetic chitosan for the preparation of a nanocomposite dye adsorbent. Langmuir. 2013;29:1657–1668. doi: 10.1021/la304696y. [DOI] [PubMed] [Google Scholar]
  49. Sun H. Cao L. Lu L. Magnetite/reduced graphene oxide nanocomposites: one step solvothermal synthesis and use as a novel platform for removal of dye pollutants. Nano Res. 2011;4:550–562. doi: 10.1007/s12274-011-0111-3. [DOI] [Google Scholar]
  50. Zhao G. Li J. Ren X. Chen C. Wang X. Few-Layered Graphene Oxide Nanosheets as Superior Sorbents for Heavy Metal Ion Pollution Management. Environ. Sci. Technol. 2011;45:10454–10462. doi: 10.1021/es203439v. [DOI] [PubMed] [Google Scholar]
  51. Al-Mur Bandar A. Mamdoh T. J. Eco-Friendly Dye Removal Using Chitosan: Characterization and Kinetic Modeling of Methylene Blue and Methyl Orange Adsorption. Polymers. 2026;18:546. doi: 10.3390/polym18050546. [DOI] [PMC free article] [PubMed] [Google Scholar]
  52. Revellame E. Fortela D. L. B. Sharp W. Hernandez R. Zappi M. Adsorption kinetic modeling using pseudo-first order and pseudo-second order rate laws: A review. Cleaner Eng. Technol. 2020;1:100032. doi: 10.1016/j.clet.2020.100032. [DOI] [Google Scholar]
  53. El-Sharkaway E. A. Kamel R. M. El-Sherbiny I. M. Gharib S. S. Removal of methylene blue from aqueous solutions using polyaniline/graphene oxide or polyaniline/reduced graphene oxide composites. Environ. Technol. 2020;41:2854–2862. doi: 10.1080/09593330.2019.1585481. [DOI] [PubMed] [Google Scholar]
  54. El-Mekkawi D. M. Ibrahim F. A. Selim M. M. Removal of methylene blue from water using zeolites prepared from Egyptian kaolins collected from different sources. J. Environ. Chem. Eng. 2016;4:1417–1422. doi: 10.1016/j.jece.2016.01.007. [DOI] [Google Scholar]
  55. Marey A. Gado W. S. Soliman A. G. Masoud A. M. El-Zahhar A. A. Al-Hazmi G. A. A. M. Taha M. H. El Naggar A. M. A. Efficient removal of methylene blue dye from wastewater specimen using polystyrene coated nanoparticles of silica. Inorg. Chem. Commun. 2024;160:112018. doi: 10.1016/j.inoche.2024.112018. [DOI] [Google Scholar]
  56. Ahmed H. M. Kebede W. L. Yaebyo A. B. Digisu A. W. Tadesse S. F. Adsorptive removal of methylene blue dye by a ternary magnetic rGO/AK/Fe3O4 nanocomposite: studying adsorption isotherms, kinetics, and thermodynamics. Chem. Phys. Impact. 2025;10:100800. doi: 10.1016/j.chphi.2024.100800. [DOI] [Google Scholar]
  57. Albadarin A. B. Collins M. N. Naushad M. Shirazian S. Walker G. Mangwandi C. Activated lignin-chitosan extruded blends for efficient adsorption of methylene blue. Chem. Eng. J. 2017;307:264–272. doi: 10.1016/j.cej.2016.08.089. [DOI] [Google Scholar]
  58. Adel M. Ahmed M. A. Mohamed A. A. Synthesis and characterization of magnetically separable and recyclable crumbled MgFe2O4/reduced graphene oxide nanoparticles for removal of methylene blue dye from aqueous solutions. J. Phys. Chem. Solids. 2021;149:109760. doi: 10.1016/j.jpcs.2020.109760. [DOI] [Google Scholar]
  59. El-Sharkaway E. A. Kamel R. M. El-Sherbiny I. M. Gharib S. S. Removal of methylene blue from aqueous solutions using polyaniline/graphene oxide or polyaniline/reduced graphene oxide composites. Environ. Technol. 2020;41:2854–2862. doi: 10.1080/09593330.2019.1585481. [DOI] [PubMed] [Google Scholar]
  60. Tolba G. M. K. Barakat N. A. M. Bastaweesy A. M. Ashour E. A. Abdelmoez W. El-Newehy M. H. Al-Deyab S. S. Kim H. Y. Effective and highly recyclable nanosilica produced from the rice husk for effective removal of organic dyes. J. Ind. Eng. Chem. 2015;29:134–145. doi: 10.1016/j.jiec.2015.03.025. [DOI] [Google Scholar]
  61. Khalaf-Allah A. S. A. Sultan M. Abdel-Monem Y. K. El-Gamasy S. M. El-Sayed W. A. Youssef A. M. Boosting adsorption capacity of methylene blue dye by multiple functional ZnO-g-C3N4/carboxymethyl chitosan/alginate –grafted polyacrylic acid composite. Sci. Rep. 2025;15:43482. doi: 10.1038/s41598-025-29715-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
  62. Peighambardoust S. J. Ghergherehchi E. Mohammadzadeh Pakdel P. Aghdasinia H. Facile removal of methylene blue using carboxymethyl cellulose grafted Polyacrylamide/Carbon black nanocomposite hydrogel. J. Polym. Environ. 2023;31:939–953. doi: 10.1007/s10924-022-02660-6. [DOI] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

RA-OLF-D6RA08198C-s001
RA-OLF-D6RA08198C-s001.pdf (319.4KB, pdf)

Data Availability Statement

All the data obtained during experimentation is given in the manuscript.

Supplementary information (SI) is available. See DOI: https://doi.org/10.1039/d6ra08198c.

Articles from RSC Advances are provided here courtesy of Royal Society of Chemistry

RESOURCES