Core–shell magnetic Fe₃O₄@C nanospheres functionalized with active chemical groups were synthesized via a one-step template-free solvothermal process and employed to remove hexavalent chromium (Cr(VI)) in aqueous media. The structure of Fe₃O₄@C nanoparticles could be effectively adjusted by the concentration of precursor. The Fe₃O₄ core possessed a high magnetism for the convenient separation of Fe₃O₄@C from aqueous solution, and high porosity and abundant functional groups (−OH, −COOH, and C═C) of carbon layer contributed to a superior performance on Cr(VI) removal. Therein, Cr(VI) ions could be efficiently adsorbed into the carbon layer and reduced to trivalent chromium (Cr(III)) mainly by C═C, and the resulting Cr(III) were chelated by the −COOH group. Noteworthy, the carbon layer thickness, pore size, and amount of chemical groups significantly increased with the increase of Fe₃O₄@C particle size resulting in a rising removal efficiency on Cr(VI). This study provides a promising approach for removing Cr(VI) and may have a huge application potential.

中文翻译：

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具有可调节结构的功能化Fe ₃ O ₄ @C纳米球，可有效去除六价铬

通过一步式无模板溶剂热法合成了具有活性化学基团功能的核-壳磁性Fe ₃ O ₄ @C纳米球，并将其用于去除水性介质中的六价铬（Cr（VI））。Fe ₃ O ₄ @C纳米颗粒的结构可以通过前驱体的浓度有效地调节。Fe ₃ O ₄磁芯具有高磁性，可方便地分离Fe ₃ O ₄水溶液中的@C以及高孔隙率和碳层的丰富官能团（-OH，-COOH和C═C）有助于去除Cr（VI）。其中，Cr（VI）离子可以有效地吸附到碳层中，并主要通过C═C还原为三价铬（Cr（III）），并且生成的Cr（III）被-COOH基螯合。值得注意的是，碳层的厚度，孔径和化学基团的数量随Fe ₃ O ₄ @C粒径的增加而显着增加，从而导致对Cr（VI）的去除效率提高。这项研究为去除Cr（VI）提供了一种有前途的方法，可能具有巨大的应用潜力。