Sugar-capped magnetite nanoparticles for selective and efficient removal of Alizarin Red S dye from aqueous solutions: an experimental and theoretical study

As a library, NLM provides access to scientific literature. Inclusion in an NLM database does not imply endorsement of, or agreement with, the contents by NLM or the National Institutes of Health. Learn more: PMC Disclaimer | PMC Copyright Notice . 2026 Jul 3;16(35):36673–36690. doi: 10.1039/d6ra03160a Water pollution has become a big concern worldwide, due to the enormous amounts of recalcitrant chemicals and organic dyes that are released from factories on a daily basis. This study evaluates removal of Alizarin Red S (ARS) dye from water using sugar-capped ( i.e. chitosan, starch, and glucose) magnetic iron oxide nanoparticles (SMNPs). The physiochemical, structural, morphological, compositional, and magnetic properties of SMNPs were fully characterized using various techniques including TEM, XRD, FTIR, DLS, and VSM. Experimental dye removal studies showed that chitosan-coated MNPs attained the highest adsorption efficiency, rapidly removing the anionic ARS dye quantitatively within only few seconds, achieving very high adsorption capacities ( q e = ∼90 mg g−1). Starch- and glucose-MNPs were also able to remove the dye, albeit at lower adsorption abilities ( q e = ∼46 and 19.5 mg g−1, respectively). Adsorption isotherm and kinetic studies indicate that the process primarily follows the Langmuir ( R 2 = 0.967) or Freundlich ( R 2 = 0.978) isotherm models, with adsorption behavior best described by pseudo-second-order kinetics. Thermodynamic study showed a positive Δ H ° value (+21.01 kJ mol−1), confirming the endothermic nature of the adsorption process which is mainly governed by physisorption. Furthermore, the negative Δ G ° values (−3.187 to −5.767 kJ mol−1) confirm that the adsorption process is spontaneous and thermodynamically favorable. Theoretical density functional theory (DFT) calculations were employed to understand the mechanism of the dye–nano-adsorbent interactions, confirming that the observed behavior is primarily due to electrostatic and hydrogen-bonding interactions between the chitosan-MNPs and ARS anionic dye. By comparing these three different sugars, our results clearly verified how functionalization can influence dye removal efficiencies. Interestingly, regeneration studies demonstrated that chitosan-MNPs could be reused over multiple cycles while maintaining excellent recyclability (≥80%). This combination of reusability and strong adsorption efficiency highlights the potential use of chitosan-MNPs for large-scale, cost-effective, and wastewater treatment applications. This study reports fast, efficient, and selective removal of Alizarin Red S dye from water using recyclable sugar-capped magnetite nanoparticles (SMNPs), highlighting their potential use for large-scale and cost-effective wastewater treatment. Water pollution has become a big problem around the world, particularly because of chemicals and dyes that are released from factories on a daily basis.1 In particular, water-soluble organic dyes in aquatic environments present a significant risk due to their high toxicity, as well as their teratogenic and carcinogenic effects.2 This also poses a huge risk to the health of humans and other living organisms. Consequently, effective and fast removal of dyes from wastewater in novel efficient ways before their release to the environment is essential.3,4 One of the most common dyes used in industry ( i.e. textiles, printing, etc. ) is Alizarin Red S (ARS), which is a negatively charged anionic dye.5–7 It belongs to the anthraquinone family and is known for its bright red color and strong chemical stability. Chemically, it contains groups such as hydroxyl (OH) and sulfonate (SO 3 Na), which make it dissolve easily in water and attach strongly to different materials. It is a water-soluble dye that serves as a color indicator (p K a ∼ 4.6–6.5) and is extensively used across the food, textile, and dye industries, resulting in its common occurrence in industrial effluents.8 Even though ARS is useful in many applications, it can be very harmful to the environment when it enters water sources. Because it does not easily decompose and can persist in water for long periods, it can block sunlight from reaching aquatic plants and lowers oxygen levels, harming fish and other aquatic life. Some studies have also shown that dyes like ARS can be toxic and dangerous to humans and animals if not treated properly. Because of these problems, removing ARS from wastewater is extremely important. Various treatment methods have been reported in the literature for removing ARS from industrial wastewater. Commonly used methods include coagulation flocculation, electrocoagulation, microbial decomposition, advanced oxidation processes ( i.e. Fenton and photocatalysis), membrane filtration, and adsorption.9–11 Traditional treatment methods like filtration or chemical oxidation are often expensive and not very effective. Even though membrane filtration provides good separation efficiency, however, it suffers from membrane fouling, high maintenance cost, and limited long-term stability.11 Coagulation and flocculation are relatively simple and low cost, but they often generate large amounts of sludge and may not completely remove highly stable dyes like ARS. Advanced oxidation processes are effective in breaking down organic dyes, but they require expensive chemicals, controlled pH conditions, and high energy input, making them less practical for large-scale wastewater treatment. Recently, scientists have focused on using nanomaterials to remove dyes, particularly ARS, from water by simple adsorption.12–14 Examples include nanocomposites,15 activated carbon and biochars,16,17 carbon nanotubes,18 hydrogels,19 zeolites,20 molecularly imprinted polymers (MIPs),21 metal–organic frameworks (MOFs),22,23 porous and mesoporous materials,24,25 and magnetic metal oxides.26 Various adsorbent materials, including activated carbon and modified clays,27 have been employed for this purpose but their cost and regeneration challenges reduce their practicality for industrial applications. Due to these limitations, research efforts have shifted towards developing advanced adsorbent nanomaterials with enhanced capacity, improved selectivity, and more efficient recovery. In particular, iron oxide magnetic nanoparticles (MNPs) coated with various polymers/surfactants have shown great potential in this regard.28 MNPs are widely regarded as highly effective nano-adsorbents due to their tunable surface chemistry, large surface-area-to-volume ratio, good biocompatibility, low synthesis cost, strong magnetic responsiveness enabling easy recovery.29–31 They can be easily separated from water using a magnet, eliminating the need for filtration or centrifugation. Although bare iron oxide MNPs have shown promise as dye absorbents in many research reports,32–35 their practical applications remain limited by their relatively low adsorption capacities, inadequate selectivities, and lack of functionalized active sites on their surfaces. Appropriate coatings on their surfaces help increase the surface area, improve the stability in aqueous environments and the biocompatibility, and enhance selectivity, leading to more effective interactions with the specific dyes.28,36,37 Therefore, employing magnetic nano-based materials for dye removal applications proves to be a simple, efficient, and cost-effective approach, effectively eliminating dye molecules on demand while enabling the reuse of the adsorbents.38,39 Using such an eco-friendly nano-based adsorption method presents a sustainable alternative to traditional dye removal techniques. In this study, iron oxide MNPs coated with sugars ( i.e. chitosan, starch, and glucose) were prepared and tested for their ability to remove ARS dye from water. The physicochemical, structural, and morphological properties of the sugar-coated MNPs (SMNPs) were characterized using different spectroscopic and electronic techniques (including XRD, TEM, DLS, FTIR, and VSM). Dye removal studies demonstrated that the as-synthesized MNPs rapidly and selectively adsorb ARS dye—within just a few seconds—exhibiting high adsorption capacities, particularly for chitosan-MNPs. Detailed adsorption isotherm, kinetic, thermodynamic, and DFT studies were also investigated. The results presented here underscore the potential of SMNPs as effective magneto-responsive nano-adsorbents for the selective, rapid, and efficient removal of ARS dye from aqueous solutions. Iron( ii ) sulfate heptahydrate (FeSO 4 ·7H 2 O), iron( iii ) chloride hexahydrate (FeCl 3 ·6H 2 O), chitosan, glucose, starch soluble (Ex Potato), 28% ammonium hydroxide (NH 4 OH), and ARS organic dye were all purchased from Sigma-Aldrich or Fisher Scientific. All chemicals and solvents were used directly without any further purification. All reactions were conducted under inert nitrogen atmosphere. The crystalline structures of all prepared MNPs were characterized using an X-ray diffractometer (Rigaku Ultima IV, Cu Kα radiation, λ = 1.5406 Å) operated at 40 kV and 30 mA over a 2 θ range of 20°–80° with a scan rate of 2° min−1 at ≈25 °C. The crystalline structural parameters were obtained through Rietveld analysis. Fourier transform infrared (FTIR) spectra (400–4000 cm−1) were recorded as KBr pellet forms using Shimadzu IRAffinity-1. TEM images were collected on a JEOL-JEM 1230 operating at 120 kV using Gatan camera with DigitalMicrograph imaging software. TEM image analysis was used where size distributions were performed using ImageJ code software. Magnetic characterizations were performed using vibrating sample magnetometer (VSM) with 1.8 T magnets at ambient temperature. UV-vis absorbance was recorded at λ max = 510 nm with a GENESYS™ 10S UV-vis. A handheld permanent magnet was used for the magnetic separation of the adsorbents, while a Julabo SW22 orbital shaker was used to conduct all dye adsorption experiments. SMNPs were prepared using our previously reported KHB method.40,41 Briefly, FeCl 3 ·6H 2 O (0.30 g) was mixed with 0.20 g of the different sugars, followed by addition of FeSO 4 ·7H 2 O (0.20 g) and stirred at 80 °C under nitrogen gas for few minutes. Approximately 3 mL of 28% NH 4 OH was added dropwise, causing the solution to turn black, indicating the formation of magnetite NPs. The mixture was then stirred for an additional 3 h. The resulting MNP suspension was purified by centrifugation and repeatedly washed with isopropanol, ethanol, and deionized water, before being dried at 80 °C for use in subsequent experiments. A 1000 ppm ARS stock solution was first prepared and subsequently diluted to obtain working solutions of 20–100 ppm. Different amounts of SMNPs (2.5–20 mg) were then added to 5 mL of each dye solution. The mixtures were briefly sonicated and gently shaken on a rotary shaker for predetermined contact times (2, 5, 10, and 20 min) under neutral pH conditions. Following adsorption, the MNPs were separated from the solutions using a handheld magnet. The absorbance of the remaining dye in the supernatant was then recorded using UV-vis spectroscopy, and dye concentrations were determined from a calibration curve (Fig. S1). The following equation was employed to calculate the removal efficiency percentage: % removal = ( C 0 − C e )/ C 0 × 100 while the maximum adsorption capacity (mg g−1) was calculated by the following: q e = ( C 0 − C e ) × ( V / m ) where C 0 and C e are the initial and equilibrium ARS dye concentrations (mg L−1), respectively. The volume of the solution and the MNP weight are denoted by V (L) and m (g), respectively. For the kinetic studies, 5 mg of each SMNPs was mixed with 5 mL of ARS dye solution of fixed concentration for varying time intervals, with continuous shaking until the dye was completely removed from the solution as evident by UV-vis. Adsorption capacity ( q e ) measurements for ARS dye were performed by shaking 5 mg of SMNPs with 5 mL aqueous ARS dye solutions of different concentrations (20–150 ppm) for 10 min at room temperature and neutral pH. The concentrations of unabsorbed dye were determined from UV-vis spectra of the supernatant by applying a hand-held magnet. For thermodynamic study, 5 mg of chitosan-MNPs was mixed with 5 mL of ARS dye solution (40 ppm) at different temperatures (293–323 K), with continuous shaking using a precise temperature-controlled heated water bath. As before, the reaction was stopped by applying a hand-held magnet and the concentrations of unabsorbed dye were determined from UV-vis spectra. The Gaussian 16 (ref. 42) software was used to perform DFT43 calculations for the geometry optimization. The B3LYP44 functional and 6-31G(d,p) basis set were used to optimize the geometries.45 Geometry optimizations and frequency calculations were carried out using the default ultrafine numerical integration grid implemented in Gaussian software to ensure reliable evaluation of exchange–correlation integrals. The initial configurations of Alizarin Red S (ARS) dye, chitosan, starch, glucose and their complexes were constructed using GaussView 6.0 software. GaussView 6.0 software-package was also used to visualize the results.46 Several initial adsorption configurations were examined during geometry optimization to obtain the most stable structures. Additionally, energies of HOMO & LUMO and bandgaps were computed for ARS, chitosan, starch, glucose, and their complexes. To investigate the effect of the solvent on the interaction between adsorbent (chitosan, starch and glucose) and ARS dye, the IEFPCM (Integral-Equation Formalism-Polarizable Continuum Model) was employed.47 Water was selected as the solvent to evaluate the stability, solubility, and adsorption behavior of the dye–adsorbent complex. Fe 3 O 4 core was not explicitly included in the DFT calculations, as it primarily acts as a magnetic support while adsorption mainly occurs on the polymer-coated surface through the polymeric functional groups. Based on the adsorption energy, the dye@adsorbent complexes' relative stability was examined. Calculations of adsorption energy ( E ads ) were performed by utilizing the below equation. E ads = E ARS@adsorbent − ( E ARS + E adsorbent ) 1 where E ARS@adsorbent indicates the energy of the complex formed between the ARS dye and chitosan, starch, and glucose, E ARS is energy of ARS dye, and E adsorbent is the energy of chitosan, starch, and glucose-MNPs, respectively. Although the B3LYP functional is widely used for investigating adsorption and electronic properties, it may underestimate long-range dispersion interactions such as van der Waals forces. Therefore, Grimme's D3 dispersion correction48 was incorporated into the calculations to achieve a more accurate description of intermolecular interactions and adsorption energies between the dye molecules and the adsorbent surface. To characterize the reactivity of complex compounds, HOMO–LUMO energy gap ( E H–L ) and various reactivity parameters including hardness ( η ), electrophilicity index ( ω ) and chemical potential ( µ ) were calculated using the provided equations below: Weak intermolecular forces between complex components were highlighted by using RDG-NCI analysis (non-covalent interaction).49–51 Three color schemes are used in RDG isosurfaces to indicate the kind of interaction. Red denotes steric repulsion, blue denotes strong interactions, and green denotes weak interactions.52 Additionally, the 3D iso-surface of RDG-NCI analysis was visualized using Multiwfn and VMD software.53 The synthetic scheme for producing various sugar-capped iron oxide magnetic nanoparticles (SMNPs) is illustrated in Fig. 1. This process utilizes our recently developed Ko-precipitation Hydrolytic Basic (KHB) method, which allows the synthesis of stabilized, controlled, and colloidally dispersed MNPs. The method relies on the stepwise in situ basic hydrolytic co-precipitation of Fe3+ and Fe2+ salts in the presence of stabilizing sugar polymers ( i.e. chitosan and starch). Addition of NH 4 OH results in the formation of black ultra-small SMNPs, that after purification are ready to be used for subsequent dye removal experiments. To verify the successful formation of SMNPs, a series of characterization techniques including FTIR, XRD, TEM, and VSM were carried out. TEM images revealed that all MNPs possessed a uniform quasi-spherical morphology, with average particle sizes ranging between 10 nm and 15 nm, as illustrated by their corresponding particle size-distributions (Fig. 2). To analyze the crystallinity and confirm the phase composition of the as-prepared SMNPs, XRD measurements were conducted. The resulting diffraction patterns for all SMNP samples are presented accordingly. Fig. 3a displays well-crystalline, single-phase inverse spinel structures. The distinct and well-resolved diffraction peaks in each pattern indicate that the samples possess high crystallinity. The cubic spinel structure of pure Fe 3 O 4 (JCPDS #01-088-0315) appeared in all samples through the characteristic sharp peaks of (220), (311), (400), (422), (511), (440), and (533) corresponding to diffraction peaks at 2 θ = 30.16°, 35.49°, 43.01°, 53.78°, 57.21°, 62.73° and 74.54°. The absence of any additional peaks ( i.e. (210) or (211)) of γ-Fe 2 O 3 patterns (JCPDS #39-1346),54–56 further indicates that the as-synthesized materials consist solely of pure inverse cubic spinel magnetite phase. It should be noted that the XRD pattern of chitosan-MNPs shows slightly reduced peak intensities, which can be attributed to chitosan's strong surface-coating ability, where its amino and hydroxyl groups coordinate with the iron core. Rietveld refinement analysis supported these findings, confirming crystallite sizes between 7.85 nm and 15 nm, and lattice parameters ( a = b = c = 8.370/81 Å) with an excellent agreement between the observed and calculated patterns (Table S1). FTIR was subsequently carried out to verify the successful sugar coating onto the MNPs (Fig. 3b). The presence of the iron oxide core is expressed by the characteristic Fe–O stretching vibrations observed at 560–620 cm−1. Distinct peaks at 2850 and 2920 cm−1 correspond to the C–H stretching modes of the sugars, while the broad band around 3400 cm−1 is attributed to O–H and NH 2 stretching vibrations from hydroxyl and amino groups (in case of chitosan). The chitosan coated sample also exhibited a peak around 1550 cm−1 associated with N–H bending, confirming the presence of amino groups.57 Additional peaks near ∼1100 cm−1 corresponds to the C–O–C stretching vibrations characteristic of the sugar backbone. All this indicates the successful functionalization of the MNP surfaces with specific sugars, mainly through hydrogen bonding, in accordance with earlier observations. Next, the surface charges of the different SMNPs were evaluated by measuring their zeta potentials ( ζ ) (Fig. 3c). Average zeta potentials in aqueous MNP dispersions were found to be as follows: chitosan-MNPs ( ζ = +44.5 ± 2.53 mV), starch-MNPs ( ζ = −0.595 ± 0.855 mV), and glucose-MNPs ( ζ = −14.2 ± 0.321 mV). These results are notable because the positive zeta potential of chitosan-MNPs is attributed to the positively charged nature of chitosan polymer capping the MNP surfaces, whereas the slightly negative zeta potentials observed for starch-MNPs and glucose-MNPs are associated with the presence of hydroxyl groups. Finally, field-dependent magnetization measurements were performed to evaluate the magnetic properties of the various SMNPs. Fig. 4a shows the hysteresis loop ( M – H ) of the different SMNPs at room temperature. All magnetic parameters are depicted in Table 1. It can be seen that all MNPs exhibit superparamagnetic behavior, with minimal and nearly negligible coercivity ( H c ) ( H c ∼ 0) and remanence ( M r ) ( M r < 1) (Fig. 4a, inset). The saturation magnetization ( M s ) obtained for the chitosan-MNPs, starch-MNPs, and glucose-MNPs were found to be equal to 23.4, 36.3, and 37.6 emu g−1, respectively indicating a high level of magnetic order and crystallinity. To validate the distinct magnetic characteristics of the various SMNP samples, the effective anisotropy constant ( K eff ) was determined using the law of approach to saturation (LAS), based on the following equations. To further confirm the unique magnetic behavior of the different SMNP samples, the law of approach to saturation (LAS) was used for calculating the effective anisotropy constant ( K eff ) by applying the following equations: where the parameter b is obtained by fitting the experimental magnetization data to the above equation. Then, K eff is then determined from the following relationship: MNPs sample M s (emu g−1) (experimental) M s (emu g−1) (LAS fit) H c (Oe) M r (emu g−1) M r / M s K eff (erg cm−3) Glucose-MNPs 37.6 37.84 0.008 0.62 0.02 2.01 × 105 Starch-MNPs 36.3 36.79 0.011 0.55 0.01 1.94 × 105 Chitosan-MNPs 23.4 23.65 0.016 0.67 0.03 1.25 × 105 As can be deduced, all of the recorded M – H hysteresis curves showed excellent agreement with the LAS model and yielded notably high K eff values of ∼1.25 × 105 to 2.01 × 105 erg cm−3 (Table 1 and Fig. 4b). With the as-synthesized SMNPs in hand, dye-removal experiments were next evaluated. Nanocomposite materials are widely recognized for their potential in adsorbing organic dyes from wastewater, prompting interest in assessing the performance of our tailored SMNPs. The anionic ARS was chosen as representative dye pollutant due to its widespread use in wastewater treatment studies. Initially, the adsorption behavior of ARS in the presence of the different SMNPs (chitosan, starch, and glucose), was tested at fixed dye concentration of 40 ppm, monitored using UV-vis spectroscopy (Fig. 5–7). This investigation aimed to determine how effectively the coated MNPs are capable in removing the dye from solution. UV-vis spectrum of ARS typically exhibits a strong absorption peak at 510 nm, corresponding to its maximum absorbance, reflecting dye initial concentration. A reduction in this peak intensity indicates a decrease in dye concentration, signifying enhanced removal efficiency. As evident in Fig. 5, chitosan-MNPs achieved extremely rapid dye removal across all dosages (2.5, 5, 10, and 20 mg) with adsorption occurring within only few seconds (<120 s). These very promising data were also visually observable with the naked eye (Fig. S2). Even at very low MNP concentrations (5 mg NPs equivalent to 1 mg mL−1), ARS dye was rapidly removed completely. At the lowest dosages (∼0.5 mg mL−1), chitosan-MNPs will still show dye removal, however, to a lesser extent. These results confirm that increasing the adsorbent dosage enhances dye removal efficiency due to larger surface area and more available binding sites. Notably, the results were reproducible, as repeated experiments using different MNP batches showed identical removal efficiencies. FTIR was performed to investigate ARS–MNP interactions before and after dye adsorption onto chitosan-MNPs. Delightfully, the spectra indicated the same characteristic vibrational peaks as the free ARS dye, further confirming the successful and fast adsorption of the dyes onto chitosan-MNPs (Fig. S3). Interestingly also, when surface charge zeta potential measurements of ARS dye after adsorption was conducted, average zeta potentials of ζ = +16.5 ± 0.513 mV was recorded, indicating the successful adsorption of ARS dye onto chitosan-MNPs (Fig. S4). This superior performance results from the cationic nature of chitosan, where protonated amino groups (NH 3 +) strongly attract the anionic sulfonate groups of ARS. Hydrogen bonding between the hydroxyl (OH) and amino (NH 2 ) groups of chitosan and the functional groups of ARS dye further enhance this interaction. The combination of positive surface charge, high density of active groups, and improved dispersion explains both the fast and high adsorption capacity observed. Starch-MNPs, on the other hand, displayed noticeably lower removal efficiencies and slower dye adsorption compared to chitosan-MNPs (Fig. 6). For 20 mg of starch-MNPs, the peak intensity decreased progressively, suggesting ongoing adsorption but with slower kinetics. When the dosage was gradually reduced to 10 mg and 5 mg, the adsorption was slightly lower (still 40–50% of dye was removed), and at 2.5 mg, only slight changes were detected. This indicates that starch-MNPs exhibit much lower adsorption efficiency compared to chitosan-MNPs. Starch contains only neutral hydroxyl groups (OH), which interact with the dye primarily through weak hydrogen bonding. Experimental observations also showed that starch-MNPs reach a clear saturation limit, after which no further adsorption occurs. This behavior indicates the presence of a limited number of adsorption sites; once these are occupied, the adsorption process is seized. In addition, the polymeric and bulky structure of starch could limit the diffusion of dye molecules toward the NP surface, reducing the effective contact between the adsorbent and the adsorbate. Finally, glucose-MNPs were examined to determine whether the sugar monomer itself influences the adsorption behavior. Similar to starch, glucose-MNPs also reached a saturated point during adsorption experiments, where adsorption ceased despite additional interaction time. The 20 mg sample demonstrated a sharp decline in absorbance, indicating efficient removal of ARS, while lower dosages (10 mg and 5 mg) showed moderate decreases, and the 2.5 mg sample displayed only a minor decrease (Fig. 7). This confirms that glucose, containing only hydroxyl groups, provides a limited number of active sites. Adsorption is driven mainly by hydrogen bonding, which is inherently weaker than the electrostatic interactions responsible for chitosan's performance. It is important to note that all the experiments of dye removal were conducted under neutral pH conditions, which is consistent with previous studies that identified an optimal pH range of 6–8 for ARS removal.57,58 In summary, these notable results can be largely attributed to key factors such as the surface chemistry and functional groups of the sugars capping the MNPs.34 While the functionalized sugars provide high density of binding sites, they also enhance the dispersion stability of the SMNPs, making them well-dispersed in aqueous solutions and, thereby, maximizing their interaction with the dye molecules. Each of the sugars provides distinct chemical characteristics that influence the adsorption mechanisms. Chitosan is a cationic polysaccharide containing protonated amino groups (NH 3 +), which provide a strong positive surface charge and create favorable electrostatic attractions with anionic dyes. Starch, on the other hand, is a neutral polysaccharide composed mainly of hydroxyl (OH) groups, offering limited adsorption sites, and interacting primarily through hydrogen bonding. Glucose, a monosaccharide, also contains hydroxyl groups; however, its lower hydroxyl group density compared to starch results in reduced intermolecular interactions. By comparing these three different sugars, our work clearly showed how surface charge and coating the MNP structures can influence dye removal efficiency (Fig. 8). As can be seen, and as general trend, as the amount of SMNPs increases, the dye removal efficiency improves correspondingly with minimal amount of dye remaining in solution. This enhancement is primarily attributed to the increased number of functional groups and active adsorption sites, along with the larger available surface area to volume ratio resulting from the higher adsorbent dosage. It is worth noting that although bare Fe 3 O 4 NPs have been reported as dye adsorbents (particularly for cationic dyes) in previous studies,36,59,60 their practical applicability remains limited because of their poor dispersibility in water, which leads to low adsorption capacities and limited selectivity. In our experiments, and as expected, when bare uncoated bare Fe 3 O 4 NPs ( ζ = −12.0 ± 0.551 mV) were tested towards removing the anionic ARS dye from solution, they were found to be the least effective (Fig. S5). Overall, in comparison to other magnetic nanomaterials in the literature, the adsorption performance of chitosan-MNPs is, thus, superior (Table S2). It should be emphasized that any direct comparison should only be made after thoroughly evaluating all experimental conditions, including the nature of the nanoadsorbents, adsorbent dosage, adsorbate and dye concentrations, temperature, shaking time and speed, contact time, and pH, as all of these factors can significantly influence the reported maximum adsorption capacities and kinetics. Thus, functionalizing MNPs with appropriate sugar biopolymers possessing plenty of functional groups is an excellent strategy to tremendously enhance the dye adsorption and removal efficiency. Therefore, we prove that coating MNPs with suitable polymers is essential to enhance their dispersion, biocompatibility, and stability in aqueous environments, thereby improving the efficiency and selectivity of dye removal. Remarkably, the extremely short adsorption and equilibration times achieved (only few seconds) indicates the potential for applying the designed SMNPs, especially chitosan-MNPs, for industrial-scale up removal of ARS dye from wastewater. Adsorption is a surface-based process driven by both physical and chemical forces, in which ARS dye molecules migrate from the liquid solution and attach to the surface of the adsorbent material.61 To gain clearer insight into the adsorption behavior, both adsorption kinetics and isotherms were examined. First, the equilibrium adsorption capacities ( q t ) were determined at different time intervals ( t ) taking fixed ARS dye concentration (40 ppm) and 5 mg of each SMNPs. As can be seen, the obtained values of q t are plotted vs. time in Fig. 9a. The adsorption of ARS dyes was very fast particularly for chitosan-MNPs reaching equilibration times in only 5 min, followed by starch-MNPs and glucose-MNPs reaching equilibration within 20 min. Thus, the equilibrium adsorption capacities are achieved in less than 30 min for all SMNPs and reached a plateau with further increase in time interval. These high adsorption rates are attributed to the abundant active sites on the surface of MNPs, which are available for adsorption, but are gradually occupied by dye molecules as time progresses. Next, adsorption experiments were carried out by exposing a fixed quantity of SMNPs (5 mg) to varying concentrations of 5 mL ARS dye solutions ranging from 20 to 120 ppm for a set period of time. Once adsorption was complete, SMNPs were removed, and the remaining dye concentration in each supernatant was determined using calibration curves to establish equilibrium values. Maximum adsorption capacity ( q e ) for each of the SMNPs was found to be equal to 90.10 mg g−1, 45.95 mg g−1, and 19.50 mg g−1 for chitosan-MNPs, starch-MNPs, and glucose-MNPs respectively (Fig. 9b). These adsorption capacities of our SMNPs are relatively excellent, as they were found to be similar or slightly higher than earlier reported Fe 3 O 4 nano-based sorbents (Table S2).7,21,57 As highlighted, the relatively high adsorption capacities attained here can be primarily attributed to the tailored sugars coating on the MNP surfaces, providing a large number of functional groups that increase the abundant active sites and create electrostatic and hydrogen-bonding sites, thereby promoting exceptionally high dye adsorption. Three different models including the pseudo-first-order, pseudo-second-order, and intraparticle diffusion were employed to evaluate the adsorption kinetics (Fig. 10a–c). Table 2 summarizes correlation coefficients and the rate constants for each model that were obtained through linear regression. The dye adsorption mechanisms explanation onto the various synthesized SMNPs relies on identifying the kinetic model that provides the strongest correlation with the experimental data. The corresponding equations for the applied kinetic models are given below.62–66 The pseudo-first-order kinetic model is expressed as follows: Kinetics model Glucose-MNPs Starch-MNPs Chitosan-MNPs Pseudo-first order Experimental q e (mg g−1) 19.50 45.95 90.10 Theoretical q e (mg g−1) 11.55 28.80 36.87 k ad (min−1) 0.065 0.014 0.193 R 2 0.952 0.951 0.925 Pseudo-second order Experimental q e (mg g−1) 19.50 45.95 90.10 Theoretical q e (mg g−1) 16.603 36.44 87.72 k s (g mg−1 min−1) 0.0138 0.001 0.022 R 2 0.991 0.967 0.999 Intraparticle diffusion C 1 (mg g−1) −0.788 −0.553 20.74 k i1 4.269 3.806 27.76 R 2 0.945 0.990 0.970 C 2 (mg g−1) 7.572 8.168 73.31 k i2 1.124 2.019 2.737 R 2 0.960 0.982 0.939 In this model, the pseudo-first-order rate constant is represented by k ad . q e (mg g−1) and q t (mg g−1) denote the adsorbed amount of ARS dye at equilibrium and at a given time t (min), respectively. The previous equation was applied to estimate the values of k ad and q e , and the corresponding correlation coefficients ( R 2) are summarized in Table 2. Due to the relatively poor linear fit obtained, the pseudo-first-order model does not adequately describe the adsorption of ARS dyes onto the SMNPs. Furthermore, the pronounced discrepancy between the theoretical and experimental q e values provides additional evidence that this adsorption process does not follow pseudo-first-order behavior. The suitability of the pseudo-second-order kinetic model for describing the adsorption behavior was assessed using the following equation: In this model, the pseudo-second-order rate constant is denoted by k s . Compared with the model of pseudo-first-order kinetics, the plot of t / q t versus t (min) produced straighter line with an excellent correlation coefficient ( R 2 = 0.999) for the adsorption of ARS dye onto the various SMNPs. Additionally, the experimentally measured q e values were in close agreement with the theoretically calculated ones, further confirming the suitability of this model. These findings indicate that the model of pseudo-second-order kinetics provides the most accurate description of ARS dye adsorption onto the SMNPs. These findings are consistent with earlier observations, where electrostatic interactions/hydrogen bonding were identified as the primary mechanism for dye removal, similar dye adsorption kinetic studies were attained.67–69 The intraparticle diffusion model is expressed by the equation: In this model, k i denotes the intraparticle diffusion rate constant, while C represents a constant. During the adsorption of ARS dye onto SMNPs, the dye molecules migrate from the bulk of the solution to the surface of the adsorbent through different transport mechanisms, including boundary-layer diffusion via external mass transfer, intraparticle diffusion, or both mechanisms. The Weber–Morris intraparticle diffusion plots (Fig. 10c) reveal that the adsorption process does not follow a single linear trend but instead exhibits two well-defined linear phases for all adsorbents. This multi-linear behavior indicates that adsorption occurs in sequential stages rather than being controlled by a single mechanism. The first linear region corresponds to rapid external mass transfer and surface adsorption, while the second region represents the slower diffusion of ARS molecules into the internal and active sites of the adsorbent. The fact that the initial linear portions of the curves do not intersect the origin indicates that intraparticle diffusion is not the only mechanism governing the adsorption rate. Instead, the process is controlled by a combination of surface adsorption and intraparticle diffusion, with the latter becoming the dominant step during the second phase of adsorption. The intercept ( C ) of the intraparticle diffusion plots provides insight into the boundary-layer effect, where higher C values indicate greater film diffusion resistance. As shown in Table 2, the boundary-layer thickness in the second stage (intraparticle diffusion) is significantly larger than in the first stage (film diffusion), suggesting that internal diffusion encounters more resistance than surface adsorption. For instance, C 1 and C 2 values for chitosan-MNPs are 20.74 and 73.31 mg g−1, respectively showing a higher value of C 2 as compared to C 1 . Furthermore, the intraparticle diffusion rate constant ( k i ) decreases markedly from the first to the second stage. The steeper slope in the first region reflects rapid surface adsorption, whereas the gentler slope in the second region indicates that intraparticle diffusion is the rate-limiting step. For instance, k i1 and k i2 values for chitosan-MNPs are 27.76 and 2.737 min−1, respectively showing a lower value of k i2 as compared to k i1 . This trend is consistent across all adsorbents, highlighting the importance of internal pore structure and accessibility in controlling adsorption kinetics. Overall, these findings confirm that the adsorption of ARS dye onto SMNPs is a multi-step process involving an initial fast phase of surface adsorption followed by a slower phase of intraparticle diffusion. The significant reduction in k i and increase in C values in the second stage emphasize that improving active site accessibility and reducing diffusion resistance are critical for enhancing adsorption efficiency. In order to understand the mechanism of interaction between the SMNP surface and the ARS dye molecules, adsorption data were evaluated for chitosan-MNPs using Langmuir, Freundlich, and Temkin isotherm models (Fig. S6). Table 3 presents the obtained correlation coefficients and constants. Overall, the experimental results aligned well with both the Langmuir and Freundlich isotherm models, although each model offers a different perspective on the adsorption behavior. Langmuir Freundlich Temkin q (mg g−1) k L (L mg−1) R 2 k F (mg g−1) 1/ n R 2 B T (mg g−1) A T (L mg−1) R 2 100.2 0.339 0.967 33 818 0.314 0.978 14.318 15.664 0.887 The calculated constants and correlation coefficients are summarized in Table 3. Overall, the experimental data showed good agreement with both the Langmuir and Freundlich models, although each provided different insights into the nature of the adsorption process. Langmuir model produced a high correlation coefficient ( R 2 = 0.967), indicating that the adsorption process can be reasonably described by monolayer coverage of dye molecules on a homogeneous surface with a finite number of identical adsorption sites. The maximum monolayer adsorption capacity ( q max ) was found to be 100.2 mg.g−1, suggesting a relatively strong affinity of the adsorbent toward the dye. This q max value reflects the potential of chitosan-MNPs for practical ARS dye removal applications. The Langmuir constant k L (0.339 L mg−1) further confirmed favorable adsorption, and this was supported by the calculated separation factor ( R L ). The R L values decreased from 0.128 at an initial concentration of 20 mg L−1 to 0.024 at 120 mg L−1, all falling within the range 0 < R L < 1. This clearly demonstrates that the adsorption process was favorable across all studied concentrations and became increasingly favorable at higher initial dye concentrations, likely based on a stronger driving force that enhances mass transfer between the MNP surface and the ARS solution. The Freundlich model yielded the highest correlation coefficient ( R 2 = 0.978), slightly outperforming the Langmuir model. This indicates that the adsorption process is more accurately described by a heterogeneous surface containing sites with different binding energies, rather than by a uniform monolayer system. The relatively high Freundlich constant ( k F = 33.818 mg g−1) further indicates a strong affinity of the adsorbent toward ARS dye. The value of 1/ n was 0.314, which is less than 1, signifying that the adsorption was both favorable and indicative of a surface with high heterogeneity. The good fit of the Freundlich model suggests the presence of different types of adsorption sites and possible multilayer formation, which is consistent with the complex structure often observed in natural or modified adsorbent materials. On the other hand, Temkin model exhibited the lowest agreement with the data ( R 2 = 0.887), although still acceptable. This model proposes that the heat of adsorption gradually decreases as surface coverage increases, a result of interactions occurring between the adsorbate molecules and the adsorbent surface. B T constant (14.318 mg g−1) and A T constant (15.664 L mg−1) values indicate moderate interactions between ARS dye molecules and the SMNPs surface. Nonetheless, the lower R 2 value compared with the Langmuir and Freundlich models suggests that the assumption of a uniform linear decrease in adsorption energy may not fully describe the system's behavior. SMNPs exhibit a more complex surface energy distribution than what the Temkin model accommodates. Taken together, these fitting data indicate that although the Langmuir model provides useful information regarding the monolayer adsorption capacity, the Freundlich model offers the best overall representation of the equilibrium data. This implies that the adsorption of the ARS dye onto SMNPs proceeds predominantly through a heterogeneous, energetically non-uniform surface with possible multilayer uptake. The favorable R L values, low 1/ n value, and relatively high q max collectively demonstrate that the chitosan-MNPs possess a strong potential for the removal of ARS dye from aqueous solutions. Thermodynamic parameters were investigated to gain deeper insights into the adsorption of ARS dye onto chitosan-MNPs over the temperature range of 293–323 K. The adsorption capacity increased with increasing temperature, indicating that the process is endothermic in nature (Fig. S7a). The thermodynamic equilibrium constant ( K d ) was defined as: The standard Gibbs free energy change (Δ G °) was calculated using: Δ G ° = − RT ln K d where, R is the universal gas constant and T is the absolute temperature. The van't Hoff equation: was applied to determine the enthalpy (Δ H °) and entropy (Δ S °) changes from the slope and intercept of the linear plot (Fig. S7b). The calculated parameters (Table 4) show a positive Δ H ° value (+21.01 kJ mol−1), confirming the endothermic nature of the adsorption process and explaining the enhanced adsorption at higher temperatures. This relatively low value of Δ H ° also suggests that the process is governed mainly by physisorption. The positive Δ S ° value (+82.39 J mol−1 K−1) indicates an increase in randomness at the adsorbent–solution interface during adsorption. Furthermore, the negative Δ G ° values (−3.187 to −5.767 kJ mol−1) confirm that the adsorption process is spontaneous and thermodynamically favorable.70–72 T (K) Δ H ° (kJ mol−1) Δ S ° (J mol−1 K−1) Δ G ° (kJ mol−1) 293 +21.01 +82.39 −3.187 303 −3.983 313 −4.537 323 −5.767 The optimized configurations of chitosan, starch, glucose, ARS dye, and the complexes (ARS@chitosan, ARS@starch and ARS@glucose) are presented in Fig. 11. The calculated dispersion-corrected adsorption-energies ( E ads (Disp)) for ARS@chitosan, ARS@starch, and ARS@glucose complexes were found to be equal to −14.98 kcal mol−1, −6.53 kcal mol−1, and +1.83 kcal mol−1 correspondingly (Table 5). Remarkably, a similar trend is observed in the aqueous phase, where ARS@chitosan remains the most stable complex with a highly negative adsorption-energy of −46.85 kcal mol−1 due to the presence of multiple intermolecular interactions, including strong H⋯O and electrostatic interactions with short bond distances. The ARS@starch complex also demonstrates favorable adsorption in water with an adsorption energy of −41.42 kcal mol−1, although its stability is lower than that of ARS@chitosan complex. Conversely, the ARS@glucose complex again exhibits positive E ads (Disp) of +21.95 kcal mol−1, confirming its weak interaction with ARS. The E ads (Disp) reveal that the adsorption affinity of ARS follows the order ARS@chitosan > ARS@starch > ARS@glucose in both gaseous and aqueous phases. The closest interacting-atoms and interaction-distances (bond lengths) for the optimized ARS@chitosan, ARS@starch, and ARS@glucose complexes in gas and water phases are presented in Fig. S8 and Table S3. The ARS@chitosan complex exhibited the strongest interaction with lowest E ads (Disp) and shortest interaction-distance of 1.86 Å, demonstrating strong-binding. The ARS@starch complex showed comparatively weaker adsorption with lower E ads (Disp) and a longer interaction-distance of 2.27 Å, suggesting moderate intermolecular interaction strength. In contrast, the ARS@glucose complex displays a positive E ads (Disp), indicating unfavorable adsorption. Overall, the results firmly demonstrate that chitosan provides the strongest adsorption capability toward ARS, followed by starch, while glucose model exhibits limited interaction capability under the studied conditions. Complex E ads (Disp) (kcal mol−1) gas phase E ads (Disp) (kcal mol−1) water phase ARS@chitosan −14.98 −46.85 ARS@starch −6.53 −41.42 ARS@glucose +1.83 +21.95 According to the quantum-mechanical theory, the interaction between the anionic ARS dye and the chitosan, starch, glucose molecules arises from HOMO–LUMO orbital interaction.73 HOMO–LUMO orbitals determine the electrons involved in donation and acceptance. The energy gap ( E H–L gap) can be used to evaluate the stability, reactivity, and type of interactions between the complex's components.74,75 The small E H–L gap indicates the enhanced chemical-reactivity and decreased kinetic-stability. The spatial-distribution of HOMO and LUMO orbitals in ARS dye, ARS@chitosan, ARS@starch, and ARS@glucose complexes are depicted in Fig. 12. The frontier molecular-orbital energies, including HOMO ( E HOMO ), LUMO ( E LUMO ), and HOMO–LUMO gap ( E H–L ) for the chitosan, starch, glucose, ARS, ARS@chitosan, ARS@starch, and ARS@glucose complexes in the gas and water phase are given in Tables 6 and S4, respectively. In gas phase, E H–L of the chitosan, starch, and glucose are 6.66 eV, 6.75 eV, and 7.54 eV, correspondingly, indicating higher electronic-stability and lower chemical-reactivity. Similarly, E H–L of the ARS dye is 0.43 eV. Upon complexation, the E H–L of the ARS@chitosan, ARS@starch, and the ARS@glucose complexes are 3.36 eV, 3.43 eV, 3.46 eV, respectively. The E H–L gaps of chitosan, starch and glucose decreased upon complexation with ARS dye. This decrease in E H–L gap indicates higher reactivity of complex-systems. In water phase, isolated chitosan, starch, and glucose molecules exhibited relatively large E H–L , whereas the ARS-based complexes showed considerably lower E H–L gaps, indicating enhanced charge-transfer interaction and increased reactivity after adsorption (Table S4). Among the complexes, ARS@chitosan exhibited the lowest E H–L and highest electrophilicity-index (6.57 eV), suggesting the strongest electronic interaction with ARS in water medium. ARS@starch also demonstrated comparable interaction behavior, while ARS@glucose complex showed relatively weaker electronic stabilization compared with the other complexes. System E HOMO E LUMO E H–L η µ ω ARS −0.23 0.20 0.43 0.21 −0.01 0.00065 Chitosan −5.89 0.76 6.66 3.33 −2.56 0.98 Starch −6.26 0.48 6.75 3.37 −2.88 1.23 Glucose −6.49 1.05 7.54 3.77 −2.72 0.98 ARS@chitosan −6.01 −2.64 3.36 1.68 −4.32 6.33 ARS@starch −6.38 −2.94 3.43 1.71 −4.66 5.57 ARS@glucose −6.00 −2.54 3.46 1.73 −4.27 5.27 The reactivity parameters are primarily used to assess a complex's chemical behavior and reactivity. Tables 6 and Table S4 provide summary of the global reactivity-parameters observed for the ARS dye, ARS@chitosan, ARS@starch, and ARS@glucose complexes in gas and water phases, respectively. The hardness ( η ) of a species reflects its resistance to deformation in the presence of an electrical-field. A higher hardness indicates less reactive and more stable system, whereas lower hardness corresponds to high reactivity and less stability.76,77 Chemical potential ( µ ) reflects the tendency of a chemical species to redistribute electron-density with its surrounding. The electrophilicity-index ( ω ) describes how well the system absorbs electron.78 According to the results, the value of η of ARS@chitosan complex is slightly less than ARS@starch and ARS@glucose complex in both gas and water phases. In the gas phase, the ω value of the complexes follows the order ARS@chitosan (6.33 eV) > ARS@starch (5.57 eV) > ARS@glucose (5.27 eV), indicating that the ARS@starch complex possesses the strongest electron-accepting ability and highest chemical-reactivity among the studied complexes. In the water phase, the ω follows the order ARS@chitosan (6.57 eV) > ARS@starch (6.41 eV) > ARS@glucose (5.95 eV), suggesting enhanced electrophilic character of the ARS@chitosan complex in solvent medium, while ARS@glucose remains comparatively less reactive in both phases. Reduced density gradient (RDG) analysis is a visualization approach used to investigate noncovalent interactions (NCIs).51,79,80 RDG-NCI analysis makes it easier to characterize interactions like hydrogen bonding, van der Waals (vdWs) interactions, and repulsive interactions. Fig. 13 shows the 3D isosurfaces and 2D NCI graphs for the ARS@chitosan, ARS@starch, and ARS@glucose complexes. The RDG 2D spectrum displays red, green, and blue colors with λ 2 ( ρ ) values ranging from −0.05 to 0.05 a.u. Intense blue spikes in the λ 2 ( ρ ) region between −0.05 and 0.02 indicates strong electrostatic interactions, which may include hydrogen-bonding. Similarly, the green region in the λ 2 ( ρ ) = 0 a.u. area show weak non-covalent bonds, such as dipole–dipole or London dispersion forces. The prominent red spikes indicate the steric repulsions when λ 2 ( ρ ) is greater than 0.01 atomic units. The strength of the interaction forces is linked with the isosurface's width.81–85 The ARS@chitosan, ARS@starch, and ARS@glucose complexes showed every kind of non-covalent interaction, as indicated by 2D NCI graphs. The presence of steric repulsion within the rings of the ARS dye molecule was showed by the red-colored peaks in 2D plots at λ 2 ( ρ ) above 0.01 atomic units. The presence of weak vdWs between ARS dye molecule and chitosan, starch, and glucose is indicated by the green-areas at λ 2 ( ρ ) −0.02 to −0.01 a.u. in the 2D NCI spectrum of ARS@chitosan, ARS@starch, and ARS@glucose complexes. Additionally, the existence of green-flakes between the chitosan, starch, glucose surface and the ARS dye is indicated by the 3D isosurface of all complexes. For the ARS@chitosan complex, the 3D isosurface (Fig. 13A) shows extensive green surfaces between ARS dye and chitosan, representing vdWs forces, alongside blue region, suggesting strong attractive interactions consistent with hydrogen bonding. The corresponding 2D RDG scatter plot exhibits dense spikes in the negative sign( λ 2 ) ρ region, confirming significant electrostatic and hydrogen bond interactions between ARS and the functional groups of chitosan. The ARS@starch complex (Fig. 13B) showed similar but comparatively moderate interaction features, with dominant green iso-surfaces suggesting stable vdWs and hydrogen bonding interactions. In contrast, 3D iso-surface of ARS@glucose complex (Fig. 13C) showed minimal green-flakes between ARS dye and glucose indicating weaker interactions. The repulsive red-flakes were the strongest among ARS@glucose complex compared to either ARS@chitosan or ARS@starch complexes. Overall, the NCI results clearly demonstrate that chitosan provides stronger NCI interactions with ARS dye, primarily due to the presence of functional groups. An effective adsorbent must demonstrate not only high adsorption capacity but also strong recyclability. In the recyclability experiments, chitosan-MNPs were tested over eight consecutive adsorption cycles to evaluate their reusability. After each cycle, the NPs were easily retrieved using an external magnet. Thanks to their high saturation magnetization and superparamagnetic behavior. The supernatant was discarded, and the MNPs were thoroughly washed with water several times, without any desorption agents, until no residual dye remained. Successive adsorption cycles were carried out using the same procedure as previously described using the regenerated magnetic nano-adsorbent. The results showed that during the first cycle, chitosan-MNPs achieved almost complete removal of ARS, reflecting their strong adsorption capacity (Fig. 14). Although a slight gradual decrease in efficiency was marked with repeated cycles, the decline was not significant, and the NPs continued to demonstrate very high removal performance across all eight cycles. Even in the later cycles, chitosan-MNPs were still able to remove a considerable amount of the dye (∼80%), which is remarkable when assessed with other reusability experiments reported in literature. These observations indicate that chitosan-MNPs has good structural stability and preserves a large portion of its active sites even after multiple uses, making it a reliable and reusable adsorbent for practical wastewater treatment applications. In summary, effective, fast, and selective removal of ARS organic dyes using MNPs functionalized with three different sugar coatings ( i.e. chitosan, starch, and glucose) was achieved. The as-synthesized SMNPs exhibited small sizes, aqueous stability, and high magnetization, enabling efficient magnetic-assisted removal of organic pollutants from water. Our dye removal experiments demonstrated that chitosan-MNPs exhibited the highest adsorption capacity, selectively and rapidly removing ARS dye within only a few seconds, thereby making them one of the most effective nano-adsorbents for ARS removal. Starch- and glucose-MNPs were also able to remove the dye, however, at lower adsorption abilities. This behavior is attributed to the positively charged nature of chitosan capping the MNP surfaces, which strongly attracts the anionic ARS molecules, whereas starch and glucose-MNPs are neutral with only hydroxyl groups, resulting in decreased adsorption efficiencies. Adsorption isotherm and kinetics indicate that the adsorption process follows the Langmuir or Freundlich models and adheres to pseudo-second-order kinetics. Thermodynamic study demonstrated that adsorption processes of ARS dye onto MNPs are endothermic and spontaneous in nature (Δ H ° = +21.01 kJ mol−1, Δ G ° = −3.187 to −5.767 kJ mol−1). DFT theoretical studies confirmed that the adsorption is primarily driven by van der Waals, electrostatic, and hydrogen bonding interactions between the sugar-coated MNP surfaces and the ARS dye, with the strongest affinity observed for chitosan@ARS complexes (ARS@chitosan complex showed the most favorable E ads = −46.85 kcal mol−1 and strongest bonding interactions). Importantly, regeneration studies displayed that the chitosan-MNPs could be reused over multiple cycles while maintaining high adsorption performance and excellent recyclability (≥80%). This combination of reusability and strong adsorption efficiency highlights the promising use for chitosan-MNPs for potential large-scaled wastewater treatment applications. Therefore, the results of this work highlight that the engineered SMNPs offer an effective, environmental friendly, and economical strategy for removing hazardous organic dyes from contaminated water, presenting a sustainable solution for both industrial and environmental wastewater. K. H. B. conceived, designed, and conceptualized the study. Z. A. S. prepared all SMNP samples and performed the dye removal experiments. W. A. A. performed the adsorption kinetics and isotherm studies. M. P. and J. I. carried out and wrote DFT theoretical part. O. M. L. and N. M. conducted magnetization, magnetic parameters, and Langevin fittings. K. H. B. and Z. A. S. analyzed the experimental data and wrote the manuscript. All authors revised and approved the manuscript. The authors declare no competing financial and/or non-financial interests in relation to the work described. This work was supported and funded by the Deanship of Scientific Research at Imam Mohammad Ibn Saud Islamic University (IMSIU) (grant number IMSIU-DDRSP2602). The authors would like to thank the continuous support of the Chemistry Department, College of Science, and the Deanship of Graduate Studies & Scientific Research at University of Bahrain (UoB). The computational part was conducted in part using the facilities of the Benefit Advanced AI and Computing Lab at UoB (https://ailab.uob.edu.bh), with support from Benefit Bahrain Company (https://benefit.bh). The authors are grateful to Mrs Alia Mustafa for helping with XRD measurements and Rietveld analyses. Finally, special and foremost thanks for Prof. Khaled Greish, Head of Clinical Research Center at Arabian Gulf University (AGU), for facilitating the use for DLS. The data that supports the findings reported herein are available upon request. 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