Performance And Mechanisms Of Lead Removal With Fe-Si-B Amorphous Alloys

Heavy metal sewage treatment is a pressing environment problem.Very recently,it is found that the Fe-based amorphous alloy could rapidily discolorate the the azo dyes wastewater and exhibit high reactivity and stability.Therotically,as a new type of zero-valent iron,the Fe-based amorphous alloy can also be used to treat wastewater containing heavy metal ions.However,most of the researches on waster treatment of Fe-based amorphous alloys focus on organic dye degradation.In this study,Pb(?)soutions were chosen as aimed contaminant,and three kinds of Fe-based amorphous alloy were used to remove Pb(?)in water.The purpose of the study was to explore their removal efficiency,internal mechanism and effects of environmental conditions.On this basis,a kind of Fe-Si-B amorphous alloy with the best performance was selected to removal various heavy metal ions with different standard redox potential.Firstly,the feasibility of Fe-Si-B amorphous alloy used as removal materials for Pb(?)in water was discussed and the removal efficiency of Fe-Si-B amorphous alloy ribbons and 300 mesh iron powders on Pb(?)in water was surveyed.Under the same conditions,the surface normalized reaction rate contants for the removal of Pb(?)by Fe-Si-B amorphous alloy ribbons could be 87 times larger than 300 mesh iron powders.It was found that the Pb(?)was removed by redox mechanism and surface adsorption by Fe-Si-B amorphous alloy ribbons,the Pb(?)was removed with surface adsorption by 300 mesh iron powders,and the reduction removal rate is greater than adsorption removal rate.Futher analysis shows that the high removal efficiency of Fe-Si-B amorphous alloy ribbons is ascribed to the amorphous structure and metalloid additions.ComParing with crystalline alloy,the Fe-based amorphous alloy in metastable state has relatively higher energy,leading to a more chemical reactivity in the statistical thermodynamics,and the addition of metalloid promote the formation of an easily detached oxide layer on the surface,which make the inner zero-valent iron easier in a more efficient way of reduction to removal Pb(?).Moreover,the removal efficiency of Fe-Si-B amorphous alloy ribbons remains 54 % after being used for 6 times in the solution containing Pb(?)ions.Based on the above work,two types of Fe-Si-B amorphous alloy powders prePared by high pressure argon gas atomization(GA)method and ball-milling(BM)method were chosen as removal materials,and the Pb(?)ions removal efficiency were studied and discussed,respectively.The results show that the Pb(?)ions removal efficiency by the two kinds of amorphous alloy powders were lager than those corresponding amorphous alloy ribbons.After reaction 20 min,a new problem occurs to BM powders because of the poor stability and easy to agglomeration;While for the GM powders,the reaction product distributes uniformly on the surface of powders and there was no agglomeration between Pariticles.And the loose mesh structure on the surface of GM powders increase the specific surface area,so as to further improve the adsorption of Pb(?)ions.Furthermore,within the studied conditions,Pb(?)ions are found to be removed by GM powders nearly within 90 min.Finally,the application of GM powders for removal of Cd(?),Ni(?),Pb(?),Cu(?),Ag(?),Cr(?)were investigated,the results shows that the removal efficiency is related to the standard redox potential of heavy metals.