零价铁表面积对泥浆反应体系中硝基苯降解行为的影响

Effects of Iron Surface Area on Reduction of Nitrobenzene-Contaminated Sediment in Slurry Reaction System

硝基苯能够被零价铁还原成为苯胺.利用气相色谱分析方法,研究了泥浆体系中零价铁表面积对硝基苯污染底质降解行为的影响.结果表明,在沉积物中初始w(硝基苯)为8.87μg/g,按照3.27 g/L最佳比例投加还原铁粉,经2 h反应约有97%的硝基苯被降解;其还原机理为表面接触反应,铁粉总表面积是影响硝基苯降解的主要参数;沉积物中硝基苯降解速率常数(K)和残留量(y)与单位体积泥浆中零价铁总表面积(ρa)之间表现为线性和负指数相关性,其关系式分别为:K=0.006 5+5.165 87×10-4ρa和y=8.57exp(-ρa/7.66)+0.25;零价铁还原硝基苯的降解过程,其降解动力学符合准一级方程,并且通过SEM扫描电镜发现零价铁在反应过程中表面被严重腐蚀,颗粒组成发生明显改变.

Nitrobenzene can be reduced to aniline by zero-valent iron metal. Effects of iron surface area on the reduction of nitrobenzene contaminated sediment were investigated by the GC analytical method in slurry reaction system. The results showed that under the conditions that the initial concentration of nitrobenzene in sediment was 8.87 μg/g and the optimum loading of iron was 3.27 g/L, more than 97% of nitrobenzene was degraded after 2 hours. The mechanism of nitrobenzene reduction by iron metal was demonstrated as surface mediated catalysis reaction, and the concentration of iron surface area in slurry was the most insignificant variable influencing the reduction. In the process of the reduction of nitrobenzene, a linear correlation was formulated between the iron surface concentrations and reaction constants, while the residual nitrobenzene in sediment decreased negative exponentially with the concentration of iron surface area, being shown as K = 0.006 5 ＋ 5.165 87 × 10^-4 ρ and y = 8.57exp（ - ρ/7.66） ＋ 0.25 irrespectively. The data of the kinetic experiment fitted well to the pseudo first-order kinetic model, while the serious corrosion on surface of iron and variety of the constitute of iron powder reduced were observed by SEM technology.