Researchers have developed a magnetic nanocomposite that effectively removes copper ions from aqueous solutions, demonstrating a maximum adsorption capacity of 341.29 milligrams per gram under optimized conditions. The material, composed of magnetite nanoparticles functionalized with anthranilic acid and chitosan, was synthesized and characterized to evaluate its potential for water remediation. This study, published in Discover Molecules, provides detailed insights into the structural properties and adsorption mechanisms of the composite, highlighting its suitability for treating heavy metal pollution in water systems.
The synthesis process involved the chemical co-precipitation of magnetite nanoparticles, which were then combined with anthranilic acid and chitosan in an acetic acid solution. The mixture was heated and subjected to ultrasonication to ensure uniform dispersion and integration of the components. The resulting nanocomposite was isolated, washed, and dried, yielding a material with a mean hydrodynamic diameter of 108.2 nanometers as determined by dynamic light scattering. This nanoscale dimension is critical for providing a high surface area, which enhances the interaction between the adsorbent and the copper ions in the solution.
Characterization techniques including scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier-transform infrared spectroscopy were employed to verify the morphology and chemical composition of the composite. The SEM images revealed a heterogeneous surface with bead-like structures, indicating the successful crosslinking of chitosan in the presence of magnetite and anthranilic acid. FTIR analysis identified key functional groups, such as O-H and N-H stretching vibrations, which play a significant role in the adsorption process. The presence of these groups suggests that the composite offers multiple binding sites for copper ions, facilitating effective removal from the water.
X-ray diffraction analysis confirmed that the magnetite nanoparticles retained their cubic spinel structure within the amorphous polymer matrix. The diffraction pattern showed distinct peaks corresponding to the (220), (311), (400), (422), (511), and (440) planes, indicating that the crystalline nature of the magnetite was preserved during the synthesis. This structural integrity is essential for maintaining the magnetic properties of the composite, which allow for easy separation and recovery of the adsorbent from the treated water using an external magnet.
The adsorption performance of the composite was evaluated under various experimental conditions, including pH, contact time, initial copper concentration, and adsorbent dosage. The results indicated that the removal efficiency was highly dependent on the solution pH, with the maximum removal of 89.89% achieved at pH 6. At lower pH values, the competition between hydrogen ions and copper ions for binding sites reduced the adsorption efficiency. Conversely, at higher pH levels, the precipitation of copper hydroxide decreased the availability of copper ions for adsorption, leading to a decline in removal efficiency.
Kinetic studies demonstrated that the adsorption process followed a pseudo-second-order model, with a correlation coefficient of 0.999. This suggests that the rate-determining step involves chemical bonding between the copper ions and the functional groups on the surface of the composite. The thermodynamic parameters further supported this finding, indicating that the adsorption process was spontaneous and endothermic. The positive enthalpy change of 56.21 kJ/mol confirmed that the process is favored at higher temperatures, likely due to improved diffusion of copper ions and increased availability of active sites on the adsorbent surface.
The isotherm data were fitted to both Langmuir and Freundlich models, with the Langmuir model providing a better fit to the experimental data. The maximum monolayer adsorption capacity was calculated to be 341.29 mg/g, reflecting the high affinity of the composite for copper ions. The favorable adsorption process was further indicated by the Langmuir constant values, which suggested that the adsorption was energetically favorable. The composite’s ability to achieve such a high adsorption capacity positions it as a competitive material for copper removal compared to other recently reported adsorbents.
To assess the practical applicability of the composite, tests were conducted using real water samples from a pond, a dam, and a river, which were spiked with copper ions. The adsorption efficiency in these real samples ranged from 64.42% to 77.17%, depending on the initial copper concentration and the specific water source. The highest efficiency was observed in river water, where the composite removed 77.17% of the copper ions. These results demonstrate the potential of the nanocomposite for use in real-world water treatment scenarios, although the study noted that the impact of competing ions in natural water systems was not investigated.
The reusability of the adsorbent was also evaluated through four successive adsorption-desorption cycles using hydrochloric acid and sodium hydroxide as eluents. The composite maintained 51.43% of its original adsorption efficiency after three cycles, indicating that it can be regenerated and reused, albeit with a gradual decrease in performance. The decline in efficiency was attributed to the strong chemisorption of copper ions, which hindered complete desorption and potentially altered some surface binding sites. Despite this, the ability to regenerate the adsorbent makes it a sustainable option for continuous water treatment applications.
The study concludes that the magnetite-anthranilic acid-chitosan nanocomposite is a promising material for the removal of copper ions from aqueous solutions. Its high adsorption capacity, rapid magnetic separation, and regenerability offer significant advantages for environmental remediation. However, further research is needed to understand the adsorption selectivity and performance in multi-component systems that more closely resemble actual water treatment conditions. The findings of this study contribute to the development of efficient and sustainable materials for addressing heavy metal pollution in water resources.
Thermal analysis provided clear boundaries for the physical resilience of the synthesized material. Thermogravimetric measurements demonstrated that the nanocomposite maintains structural stability up to 415 degrees Celsius. In differential scanning calorimetry curves, two separate endothermic events appeared between 190 and 210 degrees Celsius and between 400 and 500 degrees Celsius. The initial thermal event corresponded to the loss of physically adsorbed moisture and the dehydroxylation of iron oxide, during which structural hydroxyl groups converted into water and oxide species. The subsequent thermal event reflected the breakdown of the polymer backbone. Because no exothermic signature appeared prior to these transitions, the testing confirmed that the composite was free of unreacted monomer residues. Alongside thermal boundaries, the material’s surface charge behavior was mapped across an initial pH span of 1 to 10 in a background potassium chloride electrolyte. The point of zero charge emerged at pH 6.2, identifying the boundary where the net surface charge shifts negative. Operating just below this threshold, in the slightly acidic span between pH 5 and 6, allowed the anthranilic acid and chitosan groups to deprotonate sufficiently for copper binding without causing insoluble copper hydroxide precipitation.
Detailed infrared spectroscopy documented the specific functional groups responsible for anchoring the metal ions. Prior to adsorption, the composite displayed a broad absorbance band at 3467 reciprocal centimeters attributed to combined hydroxyl and amine stretching from the iron oxide, anthranilic acid, and chitosan. A band at 2930 reciprocal centimeters confirmed intact aliphatic and aromatic hydrocarbon structures, while a signal at 1536 reciprocal centimeters marked amine bending vibrations associated with hydrogen bonding and coordination to the iron oxide core. Absorbance at 1400 reciprocal centimeters captured interactions involving carboxylate groups, and a peak at 1260 reciprocal centimeters corresponded to aromatic carbon-nitrogen stretching. Following copper exposure, the broad hydroxyl and amine band shifted to 3424 reciprocal centimeters, while the 1260 reciprocal centimeters peak vanished entirely, signaling coordinate bond formation between copper ions and the nitrogen donors of the amine groups. Simultaneously, intensity fluctuations near 1390 reciprocal centimeters corroborated metal coordination with carboxylate functions, whereas the hydrocarbon band at 2930 reciprocal centimeters remained unchanged.
Batch testing clarified how initial metal concentrations and adsorbent quantities dictated removal efficiency and unit uptake. When initial copper concentrations increased from 50 to 300 milligrams per liter, removal efficiency dropped from 90.4 percent to 72.3 percent because active surface sites became saturated. However, the higher concentration gradient intensified the mass transfer driving force, raising equilibrium adsorption capacity from approximately 36 to over 90 milligrams per gram. When adjusting sorbent amounts from 0.006 to 0.1 grams in twenty-milliliter test volumes, removal jumped from 34.16 percent to 97.32 percent before leveling off past 0.05 grams. Conversely, unit adsorption capacity declined to 3.89 milligrams per gram at the highest dosage because surplus mass reduced the available solute per unit of sorbent. Complementing the monolayer Langmuir model, the empirical Freundlich isotherm yielded an exponent value of 1.32, with a slope of 0.7566. Because this parameter exceeded one, it confirmed favorable multilayer partitioning across a heterogeneous surface, consistent with separation factor values that remained below one across tested conditions.
Thermodynamic measurements conducted across temperatures of 301, 308, 313, and 318 Kelvin illuminated the driving forces of the capture mechanism. In addition to the positive enthalpy change, the reaction generated a positive entropy change of 191.13 joules per mole per Kelvin, pointing to increased randomness at the solid-solution boundary as hydrated water molecules were displaced from copper ions during coordination. The negative values of Gibbs free energy across all evaluated temperatures confirmed that uptake occurred spontaneously, with binding favored at higher temperatures. Spectroscopic and kinetic observations indicated that although magnetite provides the magnetic responsiveness required for physical recovery, it does not supply the primary chemical bonding sites. Instead, primary chelation is driven by the amino and carboxyl functional groups of the organic shell. The researchers noted that while the composite retained partial efficacy during cycling, regeneration using hydrochloric acid and sodium hydroxide gradually impaired active amine, hydroxyl, and carboxyl groups, while causing surface fouling and modest matrix degradation.
Subject of Research: Adsorption of Cu(II) ions from aqueous solutions using a Fe3O4-anthranilic acid-chitosan nanocomposite
Article Title: Synthesis of Fe3O4@anthranilic acid-chitosan composite: characterization and adsorption studies of Cu(II) from aqueous streams
Article References: Jadhao, J. S., Rathod, N. V., Rao, A., Ghugare, C. D., More, M. S., Kubade, A. V., Thakare, P. S., & Patil, A. B. (2026). Synthesis of Fe3O4@anthranilic acid-chitosan composite: characterization and adsorption studies of Cu(II) from aqueous streams. Discover Molecules, 3(1), Article 7. https://doi.org/10.1007/s44345-026-00048-w
Image Credits: AI Generated
DOI: 10.1007/s44345-026-00048-w
Keywords: heavy metal removal, copper adsorption, chitosan composite, magnetite nanoparticles, water treatment, nanomaterials, environmental remediation, adsorption kinetics, Synthesis, Fe3O4, anthranilic, acid-chitosan
News Source: Bethany Barker. (November 10, 2026). Magnetic Chitosan Composite Removes Copper From Water. Scienmag.
