Abstract:

With modified diatomite as support, the composite materials of nanoscale zero-valent iron and modified diatomite (NZVI-CDt) were prepared by using sodium borohydride as reducing agent via the liquid phase reduction method. The NZVI-CDt was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The influences of initial concentrations of nitrate nitrogen (5-30 mg·L^-1) and pH (3, 5, 7 and 9) on removal of nitrate nitrogen were investigated, and the final degradation products were detected. The results showed that the iron nanoparticles were highly dispersed on the surface of diatomite and several iron nanoparticles were embedded within the diatomite porous. Iron nanoparticles had a nearly spherical shape with the range of 100 nm. The NZVI-CDt showed efficient removal of nitrate nitrogen. The removal efficiency could reach 90.1% after 60 min at proper conditions:pH 7, initial 20 mg·L^-1 concentration of nitrate nitrogen and 0.5141 g NZVI-CDt at the room temperature. Kinetic studies showed that the reduction of nitrate nitrogen by NZVI-CDt followed the pseudo-first-order kinetics. In addition, kobs decreased with increasing nitrate nitrogen concentration.

Key words: modified diatomite, nanomaterials, composites, nitrate nitrogen, removal efficiency, kinetics

摘要：

以改性硅藻土为载体，采用硼氢化钠液相还原法制备了硅藻土负载的纳米铁（NZVI-CDt，nanoscale zero-valent iron supported on modified diatomite）复合材料。结果表明，所制得的纳米零价铁颗粒呈球形，粒径小于100 nm，均匀分散在改性硅藻土表面，部分纳米铁颗粒镶嵌在硅藻土孔隙内。NZVI-CDt能高效去除水体中NO₃^--N，当pH=7，温度为25℃，初始浓度为20 mg·L^-1，NZVI-CDt复合材料投加量为0.5141 g，反应60 min时，NZVI-CDt对NO₃^--N的去除率达到90.1%。NZVI-CDt去除NO₃^--N的反应符合准一级反应动力学方程，反应速率常数k_obs随着NO₃^--N初始浓度的增加而呈现下降的趋势。

关键词: 改性硅藻土, 纳米材料, 复合材料, 硝酸盐氮, 去除率, 动力学