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 Magneti

详细信息    查看全文

• 作者：Wuzhu Sun ; Weiyi Yang ; Zhengchao Xu ; Qi Li ; Jian Ku Shang
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：January 27, 2016
• 年：2016
• 卷：8
• 期：3
• 页码：2035-2047
• 全文大小：779K
• ISSN：1944-8252

文摘

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.