Abstract:

The influence of weak magnetic field (WMF) on the process of U(Ⅵ) removing by zero valent iron (ZVI) was explored and the main mechanism was investigated. The weak magnetic field could obviously promote the U(Ⅵ) sequestration under the condition of different initial pH (pH_ini). The first-order kinetic rate constants of U(Ⅵ) removal by ZVI with WMF at pH 3.0-7.0 were about 0.7 to 11.2 fold greater than those without WMF. The removal capacity of zero-valent iron toward U(Ⅵ) was 1.7 g·g^-1 with WMF at initial pH 4.0 and Fe 0.5 g·L^-1, being of 0.3-fold higher than that without WMF. The weak magnetic field could promote the corrosion of the zero-valent iron, thereby increasing its removal of U(Ⅵ), which could be verified by SEM,[Fe²⁺] and pH variation. The main mechanism of U(Ⅵ) removal by zero valent iron was adsorption together with reduction. The application of WMF did not change the mechanisms but accelerated its adsorption and reduction toward U(Ⅵ). As a chemical-, energy-free and environmental-friendly method, improving the reactivity of ZVI by WMF superimposition was novel and promising in the prospect of U(Ⅵ) sequestration from water.

Key words: weak magnetic field, zero-valent iron, U (Ⅵ), kinetics, corrosion, adsorption, removal capacity

摘要：

考察了弱磁场（WMF）对零价铁去除水中U（Ⅵ）效能的影响，并探讨了其主要机理。结果表明，在初始pH（pH_ini）为3.0~7.0，有弱磁场（w/WMF）的条件下，零价铁去除U（Ⅵ）的一级动力学速率常数提高了0.7~11.2倍。当初始pH为4.0、零价铁的投加量为0.5 g·L^-1时，弱磁场作用下的零价铁对U（Ⅵ）的去除容量为1.7 g·g^-1，相比无弱磁场（w/o WMF）时提高了约0.3倍。pH变化、Fe²⁺浓度和SEM的结果说明，弱磁场通过促进零价铁的腐蚀促进其对U（Ⅵ）的去除。从XPS光谱分析中发现，零价铁去除U（Ⅵ）的主要机理为先吸附、后还原。弱磁场只能够加速其吸附和还原过程，而不能影响零价铁对U（Ⅵ）的去除机理。弱磁场促进零价铁去除U（Ⅵ）具有价格低廉、环境友好、无须额外的能量和药剂投入等优点，因而有良好的应用前景。

关键词: 弱磁场, 零价铁, U(Ⅵ), 动力学, 腐蚀, 吸附, 去除容量