催化反硝化脱氮效果及反应机制的研究

Study on catalytic performance and reaction mechanism of catalytic denitrification

为解决水体中的硝酸盐氮污染,提出了零价铁(Fe0)耦合Pd-Cu催化剂的新型催化反硝化法去除水体中的硝酸盐氮.分别从催化反硝化操作参数的优化、反应机理及动力学等方面进行深入探讨.结果发现,用响应面曲线法对实验进行设计及分析,筛选的最佳操作条件为:溶液pH为5.0、反应时间为135min、活性组分Pd:Cu质量比为3.1、Fe0投加量为3.1g/L.在此实验条件下,催化反硝化的氮气转化率可达到74.6%.催化反应中,Fe0在催化反应中作为电子供体存在.催化剂载体负载的活性组分Pd、Cu在催化反应中发挥着重要的作用.催化剂载体的物理化学特性(如多孔结构、比表面积、吸附性能等)很大程度上影响着催化反硝化效果.通过控制溶液适宜的pH值、对催化剂载体进行酸洗处理、改变催化剂活性组分等方法可以一定程度上提高催化反硝化N2转化率.催化反硝化反应遵循Langmuir-Hinshelwood一级反应动力学规律.该催化反应是一个典型的多级反应过程.一定浓度的HCl溶液和NaOH溶液能使催化剂再生,提升催化剂的催化效果.

In order to resolve nitrate pollution in water body,the novel catalytic denitrification by synergistic effect of zero-valent iron(Fe0)and Pd-Cu catalyst was proposed.The optimization of operational conditions,reaction mechanism,and kinetic study were further investigated.Results found that using response surface methodology for experimental design and data analyses,74.6%of N2 conversion was obtained under the following optimal conditions:5.0pH,135min reaction time,3.1mass ration(Pd:Cu),and 3.1g/L Fe0.In the catalytic process,Fe0primarily serves as the electron donor.Pd and Cu coated on the carrier play critical roles in catalytic denitrification.Physical-chemical characteristics of carrier(such as porous structure,specific surface area,adsorption ability etc.)dramatically influence the catalytic performance.It’s also found that N2conversion could be greatly improved by controlling solution pH,acid wash of carrier,and replacement of catalyst’s active ingredient.Catalytic reduction of nitrate was better demonstrated by first-order equation of Langmuir-Hinshelwood modeling.Catalytic denitrification has been regarded as the typical multiphase and multistage reaction process.Acid and alkaline wash by certain concentration of HCl or NaOH solution may partially regenerate the catalyst and improve its catalytic performance.