National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Beijing 100190, China.
Environ Sci Technol. 2011 May 1;45(9):4066-72. doi: 10.1021/es104050h. Epub 2011 Apr 7.
Catalytic nitrate reduction is a promising technology in groundwater purification. In this study, PdCu bimetallic catalysts supported on an industrial amorphous silica-alumina (ASA) were synthesized and used to simulate catalytic removal of nitrate in groundwater. The catalysts exhibited very high activity and the highest catalytic selectivity toward N₂O and N₂ was 90.2%. The optimal Pd/Cu weight ratio was four. Relatively low reduction temperature was found benefit the catalytic stability and 300 °C was the appropriate reduction temperature during catalyst preparation. With an average particle size 5.4 nm, the metal particles were very uniformly distributed on the catalyst surface prepared with the codeposition method. This kept the catalyst more stable than the PdCu/Al₂O₂ catalyst with larger metal particles. According to XRD, TEM, and XPS results, the metals maintained zero-valence but aggregated by about 2 nm during the denitration reaction, which caused gradual deactivation of the catalysts. Little leaching of Cu and Pd from the catalyst might also have a slightly negative impact to the stability of the catalysts. A simple treatment was found to redistribute the particles on the deactivated catalysts, and high catalytic activity was recovered after this process.
催化还原硝酸盐是地下水净化中一种很有前途的技术。在这项研究中，制备了负载在工业用无定形硅铝（ASA）上的 PdCu 双金属催化剂，并用于模拟地下水催化去除硝酸盐。该催化剂表现出很高的活性，对 N₂O 和 N₂的最高催化选择性为 90.2%。最佳的 Pd/Cu 重量比为四。较低的还原温度有利于提高催化稳定性，在催化剂制备过程中，300°C 是合适的还原温度。采用共沉淀法制备的催化剂，金属颗粒的平均粒径为 5.4nm，非常均匀地分布在催化剂表面，这使得催化剂比具有较大金属颗粒的 PdCu/Al₂O₂催化剂更稳定。根据 XRD、TEM 和 XPS 的结果，金属在脱硝反应中保持零价，但聚集了约 2nm，导致催化剂逐渐失活。催化剂中 Cu 和 Pd 的少量浸出也可能对其稳定性产生轻微的负面影响。发现一种简单的处理方法可以重新分配失活催化剂上的颗粒，经过该过程后，催化剂的催化活性得到了恢复。
