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