Study On The Efficiency And Influences Of Azo Dye Degradation By FeBSiY Metallic Glass

Metallic glasses have attracted much attention due to their excellent mechanical properties. However, the low glass-formation ability and intrinsic brittleness limit their structural application. Metallic glasses have a complex atomic and electronic structure due to their long-range disordered atomic feature different form their crystalline counterparts, which imparts them excellent catalytic properties and opens a new chance in functional application. Degradation of azo dyes is always a big problem during swage treatment and a new high-efficient, cheap and safe solution is extremely urgent. Recently amorphous Fe powders with high degrading efficient to azo dyes were reported, however the detailed degrading mechanism is still elusive. In this paper, Fe₇₆B₁₂Si₉Y₃ metallic glass powder（G-ZVI） was fabricated by melt-spinning and subsequent ball-milling. The particle size distribution, structure, surface morphology, composition and thermodynamic parameter of the powder were studied by laser particle size analyzer, X-ray diffraction（XRD）, scanning electron microscope（SEM）, X-ray spectrometer（EDS） and differential scanning calorimetry（DSC）, respectively. Influence of the sample morphology, reaction conditions, and amorphous structure on the degradation efficiency was comprehensively evaluated in comparison to amorphous Fe₇₆B₁₂Si₉Y₃ ribbon（R-ZVI） and commercial zero-valent iron powder（C-ZVI）. The degradation mechanism of Fe-based metallic glass to methyl orange was discussed by monitoring the changes of degradation products during the reaction.The experiments results show that melt-spinning and subsequent ball-milling is effective to prepare metallic powder with uniform and well-dispersed particles of 10-40 μm. Fe₇₆B₁₂Si₉Y₃ metallic glass powder can effectively degrade azo dyes and completely remove azo double bond, including methyl orange, congo red, crystal violet and the mixture solution of four azo dye. The high-efficient degradation is mainly attributed to the amorphous structure, while the large specific surface area or strong residual stress of the ball-milled powders contributes a smaller effect. Degradation efficiency of G-ZVI to methyl orange was 18 times of R-ZVI and 1000 times of C-ZVI.Degradation reaction obeys the thermodynamics law, which indicates a faster reaction at the higher environmental temperature. Reaction activation energy was calculated as 22.6 k J/mol, which also indicates a low activation energy value and a high-efficient reaction. The p H of solution is another great influence factor to the degradation efficiency. Namely the higher the p H is, the slower degradation proceeds. The high degradation efficiency exists in neutral solution（p H=7）, then is decreased rapidly at p H of 10, and no reaction occurs at p H of 12.The degradation efficiency of Fe₇₆B₁₂Si₉Y₃ metallic glass powder remains almost unchanged after 13 cycles under these experimental conditions and then declines obviously after 20 degradation cycles, which is attributed to the oxidation products covered on the surfaces. Crystallization activation energy（Ex） of G-ZVI was 372.6 k J/mol, respectively, which indicates a stable structure against crystallization at room temperature and a long service life.The degradation efficiency of G-ZVI drops after low temperature structural relaxation and continues to drop dramatically with the onset of crystallization, which is due to the disappearance of favorable amorphous atomic nano-clusters. When compared with the Fe-rich nano-clusters, the Fe-poor regions mainly coordinate with the metalloid elements and exhibit a relatively low electro-negativity. So it is easy to envision galvanic cells between them, which promote the Fe atoms in the Fe-rich clusters to lose electrons and take part in the degradation reaction. So a large quantity of nano-galvanic cells are expected with a strong affinity for donating electrons to the reaction. The MO was decomposed into sulfanilic acid and other small molecule organics or even into carbon dioxide and water.This paper explores the high efficient degradation mechanism of azo dye by Fe₇₆B₁₂Si₉Y₃ metallic glass powders and the favorable structural conditions for effective degradation. The present findings may provide a new, highly-efficient and low cost commercial solution to azo dye waste water treatment in industrial application, and also broaden the application of metallic glasses in waste water treatment.