Development of ultra-high speed cleanup process using heterogeneous catalyst for nitrate-contaminated drinking water

在本研究中，我设定了两个目标：（1）在低浓度硝酸盐污染饮用水净化系统中，铜钯纳米团簇催化氢化硝酸盐高选择性地生成N_2;（2）在高浓度硝酸盐污染工业废水超高速净化系统中，贱金属微粒上硝酸盐的催化加氢。1.铜-钯双金属催化剂在H_2加氢NO_3-时对N_2表现出较高的选择性，但进一步抑制NH_3的形成是有待解决的问题，因为NH_3是饮用水中不希望的副产物。本研究发现，Cu-Pd纳米团簇具有均匀的活性中心，在碱性溶液中对NO_3-的加氢反应表现出独特的催化性能，即NO_3-选择性加氢为NO_2-。此外，还证明了Cu-Pd纳米团簇的存在， ...更多信息 在pH=7附近的溶液中，该催化剂对NO_2-的还原具有很高的催化活性，但对NH_3的选择性很低（3.3%）。在此基础上，提出了在碱性溶液中NO_3 ~-选择性加氢为NO_2 ~-（第一步）和在中性溶液中NO_2 ~-选择性加氢为N_2（第二步）的两步法工艺，用于处理饮用水中的硝酸盐污染。此外，用廉价贱金属制成的催化剂优于用贵金属制成的催化剂。通过对多种贱金属催化剂的筛选，发现了一种对NO_3-具有高活性的镍微粒。Zr的加入提高了催化剂的活性和稳定性，分别是由于抑制了Ni微粒的氧化和聚集。我发现的高活性贱金属催化剂是世界首例。我进一步发现，Pt添加到微粒Ni催化剂极大地提高了催化活性。该催化剂具有较高的活性，适用于含高浓度亚硝酸盐的工业废水的净化。少

In the present study, I set two objectives ; (1)for the application of cleanup system for drinking water contaminated with low concentration nitrate, catalytic hydrogenation of nitrate with high selectivity to N_2 over cupper-palladium nano-cluster, and (2)for the development of ultra-high speed cleanup system for industrial waste water contaminated with high concentration nitrite, catalytic hydrogenation of nitrate over microparticle of base metal.1.Copper-palladium bimetal catalyst has been reported to show relatively high selectivity to N_2 for hydrogenation of NO_3-with H_2, but further suppression of NH_3 formation is the problem to be solved because NH_3 is an undesired by product for drinking water. In this study, it was found that Cu-Pd nano-cluster possessing uniform active sites shows unique catalytic property for the hydrogenation of NO_3-in alkaline solution, that is, NO_3-is hydrogenated selectively to NO_2-. In addition, it was demonstrated that the Cu-Pd nano-cluster sho … More ws high catalytic activity for reduction of NO_2-with very low selectivity to NH_3 (3.3%) in the solution with near pH=7. Based on these findings, I propose the two-step process consisted of selective hydrogenation of NO_3-to NO_2-in alkaline solution (first step) and that of NO_2-to N_2 in neutral solution (second step) for the cleanup of nitrate-contaminated drinking water.2.For the cleanup of industrial waste water contaminated with high concentration nitrite, development of the catalyst possessing high catalytic activity is indispensable. In addition, the catalyst made with cheep base metal is preferred to with precious noble metal. The screening of a number of base metal catalysts found a micropaticle Ni showing high activity for the hydrogenation of NO_3-. An addition of Zr to the micropaticle Ni catalyst enhanced the catalytic activity and stability, due to suppressions of the oxidation and aggregation of Ni microparticles, respectively. The highly active base metal catalyst I found is first case in the world. I further found that an addition of Pt to the micropaticle Ni catalyst extremely enhanced the catalytic activity. The micropaticle Ni catalyst with high activity would be applicable for the cleanup of industrial waste water contaminated with high concentration nitrite. Less