Synthesis of Superparamagnetic Core-Shell Structure Supported Pd Nanocatalysts for Catalytic Nitrite Reduction with Enhanced Activity, No Detection of Undesirable Product of Ammonium, and Easy Magnetic Separation Capability.
Synthesis of Superparamagnetic Core-Shell Structure Supported Pd Nanocatalysts for Catalytic Nitrite Reduction with Enhanced Activity, No Detection of Undesirable Product of Ammonium, and Easy Magnetic Separation Capability.
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DOI：
10.1021/acsami.5b10365
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发表时间：
2016-01
影响因子：
9.5
通讯作者：
Wuzhu Sun;Weiyi Yang;Zhengchao Xu;Qi Li;J. Shang
中科院分区：
文献类型：
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作者：
Wuzhu Sun;Weiyi Yang;Zhengchao Xu;Qi Li;J. Shang
超顺磁性纳米催化剂可以最大限度地减少外部和内部的传质限制，更有效地中和反应中产生的OH（-），提高催化还原亚硝酸盐的效率，降低产物对不需要的铵的选择性，同时具有容易的磁分离能力。然而，常用的准单分散超顺磁性Fe 3 O 4纳米球不适合作为亚硝酸盐还原的催化剂载体，因为它会降低催化反应效率和产物对N2的选择性，并且铁的泄漏会给处理后的水带来二次污染。本研究以SiO2、聚甲基丙烯酸和碳为保护壳，分别制备了Fe3O4@SiO2/Pd、Fe3O4@PMAA/Pd和Fe3O4@C/Pd催化剂，用于催化还原亚硝酸根。结果表明，SiO2壳层对Fe 3 O 4纳米球核具有较好的保护作用。由于Fe3O4@SiO2/Pd催化剂分散性好、结构致密、对Fe 3 O 4有完全的保护作用，因此其催化还原亚硝酸盐的活性最高，且未检测到NH 4（+）的生成。由于这种独特的结构，Fe3O4@SiO2/Pd催化剂用于亚硝酸盐还原的活性被发现与Pd纳米颗粒的尺寸或形状无关，并且它们的产物选择性与Pd纳米颗粒的尺寸、形状和含量无关。此外，它们的超顺磁性和高饱和磁化强度使它们易于从处理过的水中磁分离，并且它们在随后的回收实验中也表现出良好的稳定性。
Superparamagnetic nanocatalysts could minimize both the external and internal mass transport limitations and neutralize OH(-) produced in the reaction more effectively to enhance the catalytic nitrite reduction efficiency with the depressed product selectivity to undesirable ammonium, while possess an easy magnetic separation capability. However, commonly used qusi-monodispersed superparamagnetic Fe3O4 nanosphere is not suitable as catalyst support for nitrite reduction because it could reduce the catalytic reaction efficiency and the product selectivity to N2, and the iron leakage could bring secondary contamination to the treated water. In this study, protective shells of SiO2, polymethylacrylic acid, and carbon were introduced to synthesize Fe3O4@SiO2/Pd, Fe3O4@PMAA/Pd, and Fe3O4@C/Pd catalysts for catalytic nitrite reduction. It was found that SiO2 shell could provide the complete protection to Fe3O4 nanosphere core among these shells. Because of its good dispersion, dense structure, and complete protection to Fe3O4, the Fe3O4@SiO2/Pd catalyst demonstrated the highest catalytic nitrite reduction activity without the detection of NH4(+) produced. Due to this unique structure, the activity of Fe3O4@SiO2/Pd catalysts for nitrite reduction was found to be independent of the Pd nanoparticle size or shape, and their product selectivity was independent of the Pd nanoparticle size, shape, and content. Furthermore, their superparamagnetic nature and high saturation magnetization allowed their easy magnetic separation from treated water, and they also demonstrated a good stability during the subsequent recycling experiment.