微纳米级天然黄铁矿负载nZVI去除水中Cr(Ⅵ)

Removal of Cr(VI)from water by micro-nano-scale natural pyrite loaded nZVI

采用机械活化(球磨)的方式,制备了微纳米级天然黄铁矿。同时以此作为载体材料,通过液相还原法制备了微纳米级天然黄铁矿负载纳米零价铁(nZVI/黄铁矿)去除水中的Cr(VI)。分析了nZVI/黄铁矿中黄铁矿和nZVI的质量比、反应初始pH对Cr(Ⅵ)去除效果的影响,并结合动力学、吸附等温线和热力学的拟合结果,对反应机理进行了探讨。结果表明,在nZVI/黄铁矿去除Cr(Ⅵ)的实验中,黄铁矿和nZVI的最佳质量比为1:2,且黄铁矿的负载加强了nZVI在酸性和碱性条件下对Cr(Ⅵ)去除能力。除此之外,nZVI/黄铁矿和nZVI对Cr(Ⅵ)去除过程均符合准二级动力学模型和Freundlich等温吸附曲线,吸附过程由物理吸附和化学吸附共同控制,为极易发生的多层吸附。反应体系中ΔG<0、ΔH>0、ΔS>0,为熵增吸热反应,可以自发进行。nZVI/黄铁矿对Cr(Ⅵ)具有更好的吸附性能和还原固定效果,反应更容易进行。以上研究结果可为天然黄铁矿和零价铁协同处理重金属的实际应用提供技术支持。

In order to remove Cr(VI)from water,micro-nano-scale natural pyrite was prepared by mechanical activation(ball milling).At the same time,as a carrier material,micro-nano-scale natural pyrite loaded nanozero-valent iron(nZVI/pyrite)was prepared by a liquid phase reduction method.The effects of the mass ratio of pyrite to nZVI in nZVI/pyrite and the initial pH of the reaction on the removal of Cr(VI)were analyzed.The reaction mechanism was discussed based on the fitting results of kinetics,adsorption isotherms and thermodynamics.The results show that in the experiment of Cr(VI)removal by nZVI/pyrite,the optimal mass ratio of pyrite to nZVI was 1:2,and the loading of pyrite enhanced the Cr(VI)removal ability of nZVI under acidic and alkaline conditions.In addition,the removal process of Cr(VI)by nZVI/pyrite and nZVI conformed to the pseudo-second-order kinetic model and Freundlich isothermal adsorption curve.The adsorption process was controlled by physical and chemical adsorption,and was a very easily occurred multi-layer adsorption.In the reaction system,ΔG<0,ΔH>0,ΔS>0,which was an entropy increase endothermic reaction and could happened spontaneously.Moreover,nZVI/pyrite had a better adsorption performance and reduction fixation effect on Cr(VI),and the reaction was easier to happen than nZVI alone.The research results can provide a theoretical basis and technical support for the practical application of natural pyrite and nano-zero-valent iron in the synergistic treatment of heavy metals.