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的饮用水净化系统中，铜-钯纳米团簇催化高选择性硝酸盐对N_2的催化加氢；(2)在工业废水高浓度亚硝酸盐污染的超高速净化系统的开发中，在贱金属微粒上，硝酸盐的催化加氢。1.铜-钯双金属催化剂在NO_3-与H_2的加氢反应中对N_2具有较高的选择性，但进一步抑制NH_3的生成是需要解决的问题，因为NH_3是饮用水中不受欢迎的副产物。研究发现，具有均匀活性中心的Cu-Pd纳米团簇在碱性溶液中对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纳米团簇具有良好的…在pH=7附近的溶液中，NO2-的催化还原活性更高，对NH3的选择性很低(3.3%)。基于这些发现，我提出了两步法，即在碱性溶液中将NO2-选择性加氢为NO2-(第一步)，在中性溶液中将NO2-选择性加氢(第二步)，以净化被硝酸盐污染的饮用水。2.对于高浓度亚硝酸盐污染的工业废水的净化，开发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比用贵重金属制成的催化剂更可取。通过对多种贱金属催化剂的筛选，发现了一种对NO_3-加氢反应具有较高活性的微粒Ni。在微米级镍催化剂中添加适量的锆，可分别抑制镍微粒的氧化和聚集，从而提高催化剂的活性和稳定性。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，在微粒镍催化剂中添加铂极大地提高了催化活性。该催化剂具有较高的活性，可用于高浓度亚硝酸盐污染的工业废水的净化。较少

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