Study On Azo Dye Degradation Properties Of Iron-based Amorphous Alloys And Their Composites

Azo dyes are widely used in textile dying,paper printing and other industries,which produce a lot of waste-water.As azo dyes are biologically toxic,the direct discharge of azo dye waste-water is hazardous to human health and causes serious environmental problems.How to efficiently degrade azo dye waste-water has become the focus of research.Fe-,Mg-,Cu-,Al-,and Co-based amorphous alloys have been reported to show a higher efficiency compared with conventional crystalline alloys in degrading azo dye waste-water due to their short-range ordered and long-range disordered atomic structures.Specifically,Fe-based amorphous alloys have been studied because of their low cost and high decomposing efficiency.In this thesis,we choose Fe-based amorphous alloys and their composite materials as the research object and explore their ability and mechanism of degrading acid orange 7.The main contents of this paper are as follow:1、The high-efficient degrading ability of FeBC amorphous ribbons toward acid orange 7via redox reactions is reported and compared with that of FePC amorphous ribbons.The time required for degrading 50%of acid orange 7 using FeBC amorphous ribbons is only 1/3 of that using FePC amorphous ribbons.In the FeBC amorphous matrix,galvanic cell structures are formed between the Fe-B and Fe-C bonds because of the large difference in their bonding strengths,which contributes to the low reaction activation energy and the high degrading efficiency of FeBC amorphous ribbons.The extremely long service life of FeBC amorphous ribbons comes from the progressive formation of 3D porous nanosheet networks due to the gradual dissolution of degradation products,allowing more efficient mass transport and a larger specific surface area.This work provides an effective and environmental-friendly Fe-based amorphous alloy for degrading azo dyes.2、The dye degradation capability and reusability of FeSi BNb Cu amorphous ribbons are largely enhanced due to the surface activation by ball milling.The time required for degrading50%of acid orange 7 by the activated FeSi BNb Cu amorphous ribbons is only 1/6 of that by the as-quenched ribbons,while the reusable times of the activated ribbons is 6 times larger than that of the as-quenched ribbons.The superior degradation capability and better reusability of the activated FeSi BNb Cu amorphous ribbons come from not only the uneven topography of the ribbon surface induced by ball milling,but also the stored deformation energy,including the structural rejuvenation and the enlarged residual stress.Two possible pathways for degradation of acid orange 7 using the activated ribbons,including azo bond cleavage and hydroxylation of benzene ring,are proposed.This work provides a new method to effectively improve the degradation performance of amorphous ribbons.3、The novel Z-scheme FeSi B/g-C₃N₄ photocatalysts with high activity under visible-light irradiation are prepared via ball milling FeSi B powders and g-C₃N₄ powders.The degradation rate to acid orange 7 of FeSi B/g-C₃N₄ photocatalysts with 75 vol.%of g-C₃N₄ is 9,6.8 and 1.4times higher than that of g-C₃N₄,Fe₃O₄/g-C₃N₄ and FeSi B catalysts,respectively.The FeSi B powders are usually wrapped by g-C₃N₄,and the heterojunction structure is formed at the interface of g-C₃N₄ and FeSi B due to the shearing stress from ball milling.The separation of photo-generated electron–hole pairs in the composite is promoted by the formed heterojunction structure,resulting in the enhancement of photocatalytic activity.It is revealed that both·O^2-and h⁺are the dominant active species throughout the photocatalytic process.Furthermore,the FeSi B/g-C₃N₄ photocatalysts exhibit a sufficient degrading capability to acid orange 7 in acidic,neutral and weak alkaline solution,and also show excellent reusability.The FeSi B/g-C₃N₄photocatalysts can be recycled from solution conveniently due to their high saturation magnetization.This work offers a novel magnetically separable photocatalyst with heterojunction structure.