催化剂在Fe^0还原污水硝态氮中的催化作用

Nitrate catalytic reduction by zero-valent iron from water over supported catalyst

为降低水体中的硝态氮对环境的危害,提高污水处理厂出水水质,将催化剂运用到零价铁还原硝态氮反应中,分别对含TiO_2及Pd的催化剂进行了探索性实验。该实验以配置的KNO_3溶液为实验水样,在比较研究添加H^+、TiO_2/Al_2O_3催化剂、Pd/Al_2O_3催化剂去除效果的基础上,深入研究了负载量、载体类型、pH、溶解氧、共存离子等因素对去除效果的影响。结果表明,催化剂TiO_2/Al_2O_3对零价铁还原硝态氮的去除率有促进作用,水样pH=3.1时去除率为72%,产物主要为氨氮,应用性较差;而催化剂Pd/Al_2O_3在pH=3.1时去除率虽为43%,但产物以N_2为主。在负载量为5%的情况下,N_2转化率为76%,这对去除总氮有重要意义,并从电子转移角度探讨了该反应的反应机理,提出了活性氢(H*)为核心的机理模型。

We herein report studies into the catalytic reduction of nitrate by metallic iron（ Fe^0） as a novel method of nitrate removal from water. Pd and TiO_2-based catalysts were employed throughout. A KNO_3 solution was used to evaluate the NO-3-N removal efficiency upon the addition of H＋,TiO_2/ Al_2O_3,and Pd /Al_2O_3. The effect of catalyst loading,support,pH,dissolved oxygen,and accompanying ions on nitrate removal were also investigated. The presence of TiO_2/ Al_2O_3 had a positive effect on nitrate removal. In addition,although the nitrate removal rate reached 72% at pH 3. 1,the dominant product was NH_4~＋-N,which has little practical application. Replacing TiO_2/ Al_2O_3 with Pd / Al_2O_3,a lower removal rate of 43% was obtained,however,the main product was N_2 gas. Furthermore,increasing the Pd loading to 5% increased the conversion rate of N_2 to 76%.Finally,the reaction mechanism was discussed on the basis of electron transfer,and a conceptual model of NO-3-N removal by zero-valent iron in the presence of a catalyst was given.