Herein, we report on the modification of nitrogen-doped graphene oxide (NGO) nanoadsorbents containing oxygen functionalities and N-containing moieties with different types of magnetic iron oxide nanoparticles (MIONPs). The physicochemical properties of the prepared NGO-MIONP nanomaterials were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM)-coupled EDS, Fourier transform infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller and zeta potential. A comparative study between the NGO modified with FeOOH (NGO-FeOOH), Fe3O4 (NGO-Fe3O4), and Fe2O3 (NGO-Fe2O3) as adsorbents for the removal of cadmium from synthetic water and acid mine drainage (AMD) was carried out. To achieve the maximum adsorption efficiency, experimental parameters were systematically studied under various conditions, including adsorption time, amount of adsorbent, solution pH and initial concentration. The comparative investigation reveals that the differences in adsorption behavior are due to differences in the surface chemistry, surface area, porosity and structural properties of the adsorbents investigated. The removal efficiency of Cd2+ from both synthetic and AMD at pH 8.0 decreased in the order: NGO-FeOOH > NGO-Fe3O4 > NGO-Fe2O3 with synthetic wastewater removal values at 97%, 96% and 93.0% respectively, while those for AMD were 99.9%, 98.4% and 96.4%. NGO-MIONPs exhibited superior maximum adsorption capacities for Cd(II) ions: NGO-Fe3O4 (87.90 mg.g−1), NGO-Fe2O3 (82.07 mg.g−1), and NGO-FeOOH (129.23 mg.g−1). Regarding the isotherm, NGO and NGO-MIONP nanoadsorbents were well fitted in the Langmuir model. Moreover, kinetic studies showed that both NGO and NGO-MIONPs were well fitted by pseudo-second-order kinetic models with a correlation coefficient (R2) ≥ 0.990. Both NGO-Fe3O4 and NGO-FeOOH nanoadsorbents were easily separated by means of an external magnetic field and were easily regenerated and reused for up to five cycles without losing significant adsorption efficiency. Therefore, the present study demonstrates that novel NGO-MIONP nanohybrids exhibited excellent Cd2+ adsorption, indicating that they are potential adsorbents for industrial wastewater treatment and AMD. Graphical abstract

Nitrogen-doped graphene oxide-based magnetic nanoadsorbents: a comparative study on removal of cadmium from acid mine drainage

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发表日期：

2025年12月4日

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K. Yokwana,
M. J. Sithole,
E. N. Nxumalo,
S. D. Mhlanga,
L. L. Noto

摘要

Herein, we report on the modification of nitrogen-doped graphene oxide (NGO) nanoadsorbents containing oxygen functionalities and N-containing moieties with different types of magnetic iron oxide nanoparticles (MIONPs). The physicochemical properties of the prepared NGO-MIONP nanomaterials were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM)-coupled EDS, Fourier transform infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller and zeta potential. A comparative study between the NGO modified with FeOOH (NGO-FeOOH), Fe₃O₄ (NGO-Fe₃O₄), and Fe₂O₃ (NGO-Fe₂O₃) as adsorbents for the removal of cadmium from synthetic water and acid mine drainage (AMD) was carried out. To achieve the maximum adsorption efficiency, experimental parameters were systematically studied under various conditions, including adsorption time, amount of adsorbent, solution pH and initial concentration. The comparative investigation reveals that the differences in adsorption behavior are due to differences in the surface chemistry, surface area, porosity and structural properties of the adsorbents investigated. The removal efficiency of Cd²⁺ from both synthetic and AMD at pH 8.0 decreased in the order: NGO-FeOOH > NGO-Fe₃O₄ > NGO-Fe₂O₃ with synthetic wastewater removal values at 97%, 96% and 93.0% respectively, while those for AMD were 99.9%, 98.4% and 96.4%. NGO-MIONPs exhibited superior maximum adsorption capacities for Cd(II) ions: NGO-Fe₃O₄ (87.90 mg.g⁻¹), NGO-Fe₂O₃ (82.07 mg.g⁻¹), and NGO-FeOOH (129.23 mg.g⁻¹). Regarding the isotherm, NGO and NGO-MIONP nanoadsorbents were well fitted in the Langmuir model. Moreover, kinetic studies showed that both NGO and NGO-MIONPs were well fitted by pseudo-second-order kinetic models with a correlation coefficient (R²) ≥ 0.990. Both NGO-Fe₃O₄ and NGO-FeOOH nanoadsorbents were easily separated by means of an external magnetic field and were easily regenerated and reused for up to five cycles without losing significant adsorption efficiency. Therefore, the present study demonstrates that novel NGO-MIONP nanohybrids exhibited excellent Cd²⁺ adsorption, indicating that they are potential adsorbents for industrial wastewater treatment and AMD.

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