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Self-Template Etching Synthesis of Urchin-Like Fe3O4 Microspheres for Enhanced Heavy Metal Ions Removal

Yu, Yong, Li, Yang, Wang, Yongqiang, Zou, Bingfang
Langmuir 2018 v.34 no.32 pp. 9359-9365
chromium, heavy metals, iron oxides, lead, magnetic separation, metal ions, microparticles, oxalic acid, surface area
Hierachical Fe₃O₄ microspheres with superparamagnetic properties are attractive for their superior structural, water-dispersible, and magnetic separation merits. Here self-template etching route was developed to create optimal porous structure in superparamagnetic Fe₃O₄ microspheres by using the oxalic acid (H₂C₂O₄) as etching agent. A plausible formation mechanism of the urchin-like Fe₃O₄ microspheres was proposed based on systematic investigation of the etching process, which involved two stages including pore-forming step based on size-selective etching and pore-expanding step based on further etching. The as-synthesized Fe₃O₄ microspheres exhibited urchin-like structure with specific surface area and pore-size tunable, water-dispersible, and superparamagnetic properties. The optimal urchin-like Fe₃O₄ microspheres demonstrated superior performance including fast magnetic separation and high removal capabilities for the heavy metals ions like Pb²⁺ (112.8 mg g–¹) and Cr(VI) (68.7 mg g–¹). This work will shed new light on the synthesis of urchin-like microspheres for superior performance.