氢气还原海绵铁去除水体中硝酸盐的研究

利用小球烧结和氢气还原工艺制备了粒径1mm～5mm的多孔性球形海绵铁,对球形海绵铁去除水体中硝酸盐的效率及去除动力学进行了研究。结果表明:溶液初始pH值对硝酸盐去除效率的影响显著,初始pH值小于3时,硝酸盐的去除率随溶液初始pH的增加而逐渐降低;初始pH值大于3时,硝酸盐的去除率又随之升高。硝酸盐浓度低于10mgN/L时,硝酸盐去除率随着硝酸盐初始浓度的增加而增加,硝酸盐的残余量保持在0.4mgN/L左右;硝酸盐浓度高于20mgN/L时,硝酸盐的去除率随初始硝酸盐浓度的增加而略有降低。球形海绵铁去除硝酸盐为一级动力学反应,反应级数为0.970～1.378,表观反应速率常数为0.314h-1～0.536h-1。海绵铁还原硝酸盐的主要产物为氨氮,随着还原反应的进行,溶液pH值快速增加,氨氮以分子态氨的形式从水中逸出。进行归纳总结和对比,并以多环芳烃的提取为例列举了各方法的应用步骤,从而为其他环境样品其他有机物分析预处理提供参考。

Nitrate Removal from Water by Spherical Sponge Iron Prepared by H2 Reduction

Porous spherical sponge iron with 1mm～5mm diameter was prepared by mini-pellet sintering integrated with H2 direct reduction. Static state experiment was done to investigate nitrate removal efficiency from polluted water by spherical sponge iron and to explore nitrate reduction reaction kinetics. Results indicated that initial pH in solution had significant influence on nitrate removal rate. Nitrate removal rate decreased with increasing of initial pH when pH value was below 3,while increased when pH value was above 3. Nitrate removal rate increased with increasing of initial nitrate concentration when it was below 10mg-N/L,with concentration of nitrate residues about 0.4mg-N/L. When initial nitrate concentration was higher than 20mg-N/L,nitrate removal rate decreased slightly with increasing of nitrate concentration. Nitrate reduction by spherical sponge iron appeared to be the first order reaction,with the reaction order 0.970～1.378 and apparent reaction rate constant 0.314h-1～0.536h-1. Major product of nitrate reduction was ammonium. Molecule-state ammonia could escape from water solution because pH value increased along with the reduction reaction carrying through.