Fe₃O₄@Mesoporous-SiO₂@Chitosan@Polyaniline Core–Shell Nanoparticles as Recyclable Adsorbents and Reductants for Hexavalent Chromium

In this work, we designed the Fe3O4@mesoporous-SiO2@chitosan@polyaniline core–shell nanoparticles (Fe3O4@mSiO2@CS@PANI, hence abbr. FSCP), which can be used to capture Cr(VI) in wastewater. Rapid adsorption behavior and high removal capability (249.6 mg Cr(VI) per gram of FSCP) were exhibited by this material. X-ray photoelectron spectroscopy (XPS) analysis demonstrates that Cr(VI) was adsorbed and in situ reduced on FSCP at pH 2. Adsorption was facilitated by the electrostatic attraction of HCrO4– and −N+═C–/–N+H–, while the active −NH–/–N+H– sparked the reduction of Cr(VI) to Cr(III). Moreover, the coordination of the resulting Cr(III) with the amino group promoted adsorption, thus achieving detoxification of Cr(VI) in wastewater. After eight recycling experiments, the Cr(VI) removal efficiency of this material is still more than 90%, indicating that this material has excellent stability and good application potential. Therefore, this magnetic adsorbent offers a potential solution for the successful handling of chromium-containing wastewater.