Preparation And Surface Modification Of Iron-based Amorphous/Nanocrystalline Alloys For Efficient Dye Degradation

Synthetic dyes not only cause trouble to environment,but also harm to human health.Therefore,the treatment of dye wastewater is significant to environmental protection.Amorphous alloy has shown great potential in the field of dye degradation in recent years,because of the unique atomic disordered structure and high catalytic activity.It provides a theoretical basis and practical feasibility for the application of wastewater treatment industry.In this paper,different iron-based amorphous/amorphous nanocrystalline alloy ribbons were prepared and investigated the degradation performance under the same experimental condition.The mechanism of the excellent degradation performance was also analyzed by means of XRD,TEM,SEM and XPS.In addition,electrochemical dealloying and chemical dealloying were used to modify the surface of alloy ribbons,and the changes of catalytic degradation performance were also investigated.In the Fe Cu BP,Fe Cu BY,Fe Zr BY,Fe Si BPCu,Fe Ti B,Fe Si B alloy ribbons,Fe₈₀Cu₄B₁₄P₂shows the best dye degradation performance.Under the simulated visible light,rhodamine B solution(20 mg/L)can be completely degraded in 8 min and the reaction rate constant is as high as 0.51 min^-1.Moreover,it has good catalytic stability.The excellent degradation performance is mainly derived from the formation of two types of galvanic cells.Galvanic cells in nanoscale can accelerate the electron transport efficiency in Fenton process and improve the generation efficiency of free radicals,and thus the dye degradation performance can be improved.Additionally,the unique three-dimensional porous network structures are formed on the surface during the degradation process.The network structures can promote the continuous catalytic degradation performance due to the increased specific surface area and the exposed fresh alloy matrix.By adjusting the composition of Fe_84-xCu_xB₁₄P₂ alloys and changing the amorphous forming ability to match the solidification conditions,iron-based nanocrystalline alloy ribbons with different volume fractions of nanocrystals were prepared only by melt-spinning method,avoiding conventional heat treatment.With Cu content increasing,the alloys change from amorphous to amorphous-nanocrystalline structure,and the volume fraction of nanocrystals increases,laying the foundation for the surface modification.The best efficiency of dye degradation is Fe₈₀Cu₄B₁₄P₂among these Fe Cu BP alloys.When the Cu content less than 4%,the number of galvanic cells was insufficient,resulting in a slower electron transport capacity.The volume fraction of amorphous decreases with Cu increases,which lead to a decrease in the number of catalytic active sites.Also,the alloy changes from amorphous metastable state to crystalline stable state,and so the catalytic performance gets worse.After dealloyed with low potential,the smooth surface of Fe₇₈Cu₆B₁₄P₂ amorphous nanocrystalline alloy ribbon is transformed into a typical nanoporous structure surface.The reaction rate constant increases from 0.244 to 0.574 min^-1,and the performance of catalytic degradation is improved significantly due to the nanoporous structure surface,which can expose more reaction sites and active substances.After dealloyed in HF solution,the catalytic degradation performance of Fe₈₀Zr₆B₁₂Y₂amorphous alloy can be significantly improved,and the degradation efficiency increases with the extension of dealloying time.It can be observed that the amorphous structure of(Fe,Y)OF can be densely distributed on the surface after dealloying.The results of electrochemical impedance shows that(Fe,Y)OF can significantly reduce the charge transfer resistance on the surface of the alloy and accelerate the electron transfer,which can speed up the generation of·OH in the Fenton reaction,and improve the dye degradation efficiency.