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)应用于低浓度硝酸盐污染饮用水的净化系统，在铜钯纳米簇上对N_2具有高选择性的硝酸盐进行催化加氢；(2)应用于高浓度亚硝酸盐污染工业废水的超高速净化系统的开发，在基本金属微粒上催化硝酸盐加氢。铜钯双金属催化剂在no_3与H_2加氢过程中对N_2有较高的选择性，但由于NH_3是饮用水中不希望出现的副产物，因此进一步抑制NH_3的生成是有待解决的问题。本研究发现，具有均匀活性位点的Cu-Pd纳米团簇对碱性溶液中no_3的加氢表现出独特的催化性能，即no_3被选择性加氢为NO_2-。此外，在pH=7附近的溶液中，Cu-Pd纳米团簇对no_2的选择性极低（3.3%）还原为NH_3具有较高的催化活性。基于这些发现，笔者提出了两步法，即在碱性溶液中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）来净化硝酸盐污染的饮用水。对于高浓度亚硝酸盐污染的工业废水的治理，开发具有高催化活性的催化剂是必不可少的。此外，用廉价贱金属制成的催化剂优于用贵重贵金属制成的催化剂。通过对多种贱金属催化剂的筛选，发现微颗粒Ni对NO_3-的加氢具有较高的活性。在Ni微颗粒催化剂中添加Zr可以抑制Ni微颗粒的氧化和聚集，从而提高催化活性和稳定性。我发现的高活性贱金属催化剂是世界上第一例。我进一步发现，在微颗粒镍催化剂中加入Pt极大地增强了催化活性。该催化剂具有高活性，可用于高浓度亚硝酸盐污染的工业废水的净化。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