Yu Sheng-Hui, Yao Qi-Zhi, Zhou Gen-Tao, Fu Sheng-Quan
CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, ‡School of Chemistry and Materials Science, and §Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China , Hefei 230026, P. R. China.
ACS Appl Mater Interfaces. 2014 Jul 9;6(13):10556-65. doi: 10.1021/am502166p. Epub 2014 Jun 18.
Hollow core/shell hematite microspheres with diameter of ca. 1-2 μm have been successfully achieved by calcining the precursor composite microspheres of pyrite and polyvinylpyrrolidone (PVP) in air. The synthesized products were characterized by a wide range of techniques including powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and Brunauer-Emmett-Teller (BET) gas sorptometry. Temperature- and time-dependent experiments unveil that the precursor pyrite-PVP composite microspheres finally transform into hollow core/shell hematite microspheres in air through a multistep process including the oxidation and sulfation of pyrite, combustion of PVP occluded in the precursor, desulfation, aggregation, and fusion of nanosized hematite as well as mass transportation from the interior to the exterior of the microspheres. The formation of the hollow core/shell microspheres dominantly depends on the calcination temperature under current experimental conditions, and the aggregation of hematite nanocrystals and the core shrinking during the oxidation of pyrite are responsible for the formation of the hollow structures. Moreover, the adsorption ability of the hematite for Sm(III) was also tested. The results exhibit that the hematite microspheres have good adsorption activity for trivalent samarium, and that its adsorption capacity strongly depends on the pH of the solution, and the maximum adsorption capacity for Sm(III) is 14.48 mg/g at neutral pH. As samarium is a typical member of the lanthanide series, our results suggest that the hollow hematite microspheres have potential application in removal of rare earth elements (REEs) entering the water environment.
通过在空气中煅烧黄铁矿与聚乙烯吡咯烷酮（PVP）的前驱体复合微球，已成功制备出直径约为1 - 2μm的中空核壳结构赤铁矿微球。采用多种技术对合成产物进行了表征，包括粉末X射线衍射（XRD）、场发射扫描电子显微镜（FESEM）、能量色散X射线光谱（EDX）、透射电子显微镜（TEM）、高分辨率TEM（HRTEM）、热重分析（TGA）、差示扫描量热法（DSC）以及布鲁诺尔-埃米特-泰勒（BET）气体吸附法。温度和时间依赖性实验表明，前驱体黄铁矿-PVP复合微球在空气中最终通过多步过程转变为中空核壳结构赤铁矿微球，该过程包括黄铁矿的氧化和硫化、前驱体中包裹的PVP的燃烧、脱硫、纳米级赤铁矿的聚集和融合以及微球内部到外部的质量传输。在当前实验条件下，中空核壳微球的形成主要取决于煅烧温度，并且赤铁矿纳米晶体的聚集以及黄铁矿氧化过程中的核收缩是中空结构形成的原因。此外，还测试了赤铁矿对Sm(III)的吸附能力。结果表明，赤铁矿微球对三价钐具有良好的吸附活性，其吸附容量强烈依赖于溶液的pH值，在中性pH值下对Sm(III)的最大吸附容量为14.48 mg/g。由于钐是镧系元素的典型成员，我们的结果表明中空赤铁矿微球在去除进入水环境的稀土元素（REEs）方面具有潜在应用。
