The heavy metals discharged from electroplating wastewater, represented as copper and chromium ions, is harmful to aquatic lives and human beings, and will break the ecological balance. In this work, magnetic hybrid porous structure adsorbent of Fe 3 O 4 @SiO 2 -UiO-66-EDTA is prepared for recycling copper and chromium ions. The adsorbent exhibits a maximum adsorption capacity of 212.10 mg/g for Cu(II) and 118.10 mg/g for Cr(VI). Notably, it shows excellent regenerability of 87.12% after 5 cycles. The adsorption of Cu(II) and Cr(VI) on Fe 3 O 4 @SiO 2 -UiO-66-EDTA follows the pseudo-second-order model, where chemical adsorption is dominant and it occurs spontaneously and exothermally. Based on XRD, FTIR, XPS, and DFT calculations, the adsorption mechanisms are driven by electrostatic attraction, chelation, and redox reactions. This work provides a novel and promising strategy for designing highly efficient adsorbents, paving the way for more effective treatments of electroplating wastewater contaminated with Cu(II) and Cr(VI).
Jianwei Zheng,Liying Zhang,Yang Li,Hong-Bin Sun,Gang Zhang,Qi Sun
Core–shell nanocomposites with a catalytic metal-organic framework (MOF) shell are more effective and stable than bare MOF. We have successfully designed an effective heterogeneous catalyst for the synthesis of benzimidazole by integrating acidic catalytic activity, and promoted the aerobic oxidation and magnetic recyclability of core–shell nanocomposite Fe3O4@SiO2@UiO-66. The Fe3O4@SiO2 core is encapsulated by the in situ-grown UiO-66 shell, and the UiO-66 shell retains the porous structure and crystallinity of UiO-66 with abundant exposed Lewis acid sites. It shows high catalytic ability for the synthesis of various benzimidazoles through the acid-catalyzed condensation and aerobic oxidation with in situ oxygen. The Fe3O4@SiO2 core provides magnetic recyclability of Fe3O4@SiO2@UiO-66, and maintains high catalytic ability and stability over six cycles.
The combination of magnetic nanoparticles and metal–organic frameworks (MOFs) has demonstrated their potential for pollutant sequestration. In this work, Fe3O4@SiO2@UiO-66 core–shell magnetic microspheres were synthesized and used for the removal of U(VI) from an aqueous environment. The characterization via transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectrometry (FT-IR), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA) and nitrogen adsorption porosimetry proved that the Fe3O4@SiO2@UiO-66 core–shell nanocomposite was successfully prepared. Batch experiments were conducted to study the effects of initial pH, shaking time and temperature on the uranium sorption efficiency. The isotherm and kinetic data were accurately described by the Langmuir and pseudo-second-order models. The maximum adsorption capacity was calculated to be 616.5 mg g−1 for U(VI) by fitting the equilibrium data to the Langmuir model. Various thermodynamic parameters were evaluated, which indicated the endothermic and spontaneous nature of adsorption. Thus, the excellent adsorption capacity and sensitive response of the Fe3O4@SiO2@UiO-66 core–shell magnetic microspheres to a magnetic field make them a promising candidate for the removal of uranium(VI) from aqueous solutions.
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