采用微乳液法制备出粒径约为80 nm,主要成分为α-Fe的纳米铁粒子。纳米铁具有极高的活性,在无氧环境中,室温、中性条件下与初始质量浓度为30、50、80、120 mg/L的NO3--N振荡反应30 m in,即可获得90%以上的脱硝率。零价纳米铁去除硝酸盐氮的一系列批实验结果表明:硝酸盐与纳米铁反应为非一级动力学反应,硝酸盐氮浓度随时间单调减少,氨氮浓度随时间单调升高,而亚硝酸盐氮的浓度在反应过程中出现极大值,由动力学分析可知其具有连续反应的突出特征,并以此对反应路径进行了探讨。提出纳米铁与硝酸盐反应是氧化还原与吸附作用同时存在且主要产物为氨氮的观点。
采用液相还原法制备了以石墨为载体的负载型纳米铁,并以其为还原剂进行化学反硝化,考察了此种材料还原硝酸盐氮的特性。结果表明,负载型纳米铁在中性条件下能够快速将硝酸盐氮还原而去除;铁量相同而不同铁碳比的负载型纳米铁还原硝酸盐氮的速率有所不同;体系初始pH值越低则负载型纳米铁还原硝酸盐氮的速率越快,pH值为2时可在15 m in内将浓度为80mg/L的硝酸盐氮全部去除;体系中的溶解氧会与NO3-争夺电子,在pH值较低时NO3-的还原受溶解氧的影响较大;负载型纳米铁可构成微小原电池,在化学反硝化反应中Fe起主要作用,Fe2+对反应有促进作用。
Nano ZVI particles supported on micro-scale exfoliated graphite were prepared by using KBH4 as reducing agent in the H2O/ethanol system. The supported ZVI materials generally have higher activity and greater flexibility for environmental remediation applications. The exfoliated graphite as the support was treated beforehand to hydrophilic material. Nano iron particles are deposited onto the rough graphite surface while those were formed by borohydride reduction. The possible nitrate reduction pathways were proposed. The TEM image shows that iron particles are highly dispersed on the surface of graphite and several of iron particles are imbedded in the pit of support surface. In this synthesis, iron particles have a nearly spherical shape with a grain size of 50?100 nm. The surface areas of materials with different iron loadings of 3.5%, 7.0%, 10.0%, 15.0% and 20.0%(mass fraction) are 2.89, 9.55, 8.45, 23.8 and 6.18 m2·g?1 by BET surface analyzer. The chemical reduction of nitrate by supported nano ZVI in aqueous solution were tested in series batch experiments. Experiment results suggest that NO3? can be more rapidly reduced to NH4+ at neutral pH and anaerobic conditions by supported nano ZVI than unsupported nano ZVI or ZVI scraps. The 15% nano Fe/graphite shows the best reduction efficiency contrasted with other Fe loading particles.
