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<p>This study presents the synthesis of an Fe<sub>3</sub>O<sub>4</sub>/rGO nanocomposite optimized with 27% (wt./wt.) Fe<sub>3</sub>O<sub>4</sub> loading for the efficient adsorption of 4-nitroaniline (4-NA) and Cr(VI) from wastewater. Various characterization techniques were employed to evaluate the structural, textural, thermal, mechanical, and physicochemical properties of the synthesized nanocomposite. X-ray diffraction (XRD) and Raman spectroscopy confirmed the formation of inverse spinel Fe<sub>3</sub>O<sub>4</sub> nanocrystals. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) revealed a quasi-homogeneous dispersion of Fe<sub>3</sub>O<sub>4</sub> nanoparticles (average crystallite size: 10.67&#xa0;nm) anchored onto rGO nanosheets. The presence of microporous networks in the nanomaterial was verified through N<sub>2</sub>-BET analysis, which demonstrated a high specific surface area of 192.8 m<sup>2</sup>/g, facilitating the adsorption of harmful contaminants. Goniometric measurements confirmed the hydrophilic nature of the adsorbent. Batch adsorption experiments were conducted at 303&#xa0;K with a fixed adsorbent dosage of 0.25&#xa0;g/L to evaluate adsorption kinetics. Equilibrium adsorption times were determined as 4&#xa0;h for 4-NA and 6&#xa0;h for Cr(VI), both following pseudo-second-order kinetics. At pH 2 and 303&#xa0;K, the nanocomposite exhibited remarkable maximum adsorption capacities of 264.21&#xa0;mg/g for 4-NA and 324.56&#xa0;mg/g for Cr(VI). High-resolution X-ray photoelectron spectroscopy (HR-XPS) analysis of spent samples revealed that the adsorption of 4-NA occurred predominantly through physical mechanisms, such as electrostatic attraction and π-π interactions between 4-NA molecules and the rGO moiety. In contrast, Cr(VI) adsorption was primarily achieved via synergistic chemical processes, including chelation with surface oxygen-functional groups (OFGs) and partial reduction to Cr(III), catalyzed by Fe<sub>3</sub>O<sub>4</sub>. With a saturation magnetization of 18.4&#xa0;emu/g, the nanocomposite can be efficiently separated from aqueous media after adsorption using an external magnet. Furthermore, the nanocomposite demonstrated robust chemical and morphological stability, retaining its adsorption capacity and showing no significant iron leaching over four test cycles for both 4-NA and Cr(VI). This highlights its potential for sustainable wastewater remediation.</p>

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Fe3O4 Nanoparticles Loaded on Hydrothermally Synthesized Reduced Graphene Oxide Nanosheets for the Efficient Removal of Aqueous p-Nitroaniline and Cr(VI)

  • 期刊论文

  • 发表日期：

    2025年12月12日

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  • Sourav Halder,
  • Lokesh Chandra Das,
  • Bhaskar Bhaduri

摘要

This study presents the synthesis of an Fe3O4/rGO nanocomposite optimized with 27% (wt./wt.) Fe3O4 loading for the efficient adsorption of 4-nitroaniline (4-NA) and Cr(VI) from wastewater. Various characterization techniques were employed to evaluate the structural, textural, thermal, mechanical, and physicochemical properties of the synthesized nanocomposite. X-ray diffraction (XRD) and Raman spectroscopy confirmed the formation of inverse spinel Fe3O4 nanocrystals. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) revealed a quasi-homogeneous dispersion of Fe3O4 nanoparticles (average crystallite size: 10.67 nm) anchored onto rGO nanosheets. The presence of microporous networks in the nanomaterial was verified through N2-BET analysis, which demonstrated a high specific surface area of 192.8 m2/g, facilitating the adsorption of harmful contaminants. Goniometric measurements confirmed the hydrophilic nature of the adsorbent. Batch adsorption experiments were conducted at 303 K with a fixed adsorbent dosage of 0.25 g/L to evaluate adsorption kinetics. Equilibrium adsorption times were determined as 4 h for 4-NA and 6 h for Cr(VI), both following pseudo-second-order kinetics. At pH 2 and 303 K, the nanocomposite exhibited remarkable maximum adsorption capacities of 264.21 mg/g for 4-NA and 324.56 mg/g for Cr(VI). High-resolution X-ray photoelectron spectroscopy (HR-XPS) analysis of spent samples revealed that the adsorption of 4-NA occurred predominantly through physical mechanisms, such as electrostatic attraction and π-π interactions between 4-NA molecules and the rGO moiety. In contrast, Cr(VI) adsorption was primarily achieved via synergistic chemical processes, including chelation with surface oxygen-functional groups (OFGs) and partial reduction to Cr(III), catalyzed by Fe3O4. With a saturation magnetization of 18.4 emu/g, the nanocomposite can be efficiently separated from aqueous media after adsorption using an external magnet. Furthermore, the nanocomposite demonstrated robust chemical and morphological stability, retaining its adsorption capacity and showing no significant iron leaching over four test cycles for both 4-NA and Cr(VI). This highlights its potential for sustainable wastewater remediation.