Degradation Of Dye Wastewater By Metallic Glasses

Recently, several metallic glasses ?MGs? were reported to degrade azo dyes successfully, and the findings pave a new way for functional application of MGs.However, the mechanisms for dye degradation, the effect of the MG composition and surface condition on the degradation behaviors have not been addressed in depth.In this thesis, a systematic study was performed on the degradation properties of azo dye by oxide Fe-based MG, Co-based and Cu-based MGs, and the electrochemical degradation properties of Fe-based MG.The degradaiton of an azo dye by oxide Fe₇₈Si₈B₁₄ MG obeys the pseudo first-order kinetic model in two stages: a slow step followed by a rapid one. This observation is in accordance with the following results, the azo dye is simply adsorbed onto the Fe₇₈Si₈B₁₄ MG powders in the initial stage, because the oxide layer coated on the powder surface depresses the degradation reaction by covering the activity sites, and then the degradation occurs with the desquamation of the powders. The azo dye could be degraded with a rapid reaction rate when the Fe₇₈Si₈B₁₄ MG powders are applied to the treatment process again, because of the consumption of the oxide layer and the unchanged core of the Fe₇₈Si₈B₁₄ MG. The surface oxide layer does not influence the reusability of the Fe₇₈Si₈B₁₄ MG in degrading azo dye.The azo dye degradation rate by Co78SiB14 MG is higher than that by the corresponding crystalline alloy and Fe-based, Mg-based MGs. The atoms in the highly coordinatively unsaturated state in Co78Si8B14 MG function as catalysts and the absorbed atomic hydrogen species are responsible for hydrogenation degradation of azo dyes. The coordinatively unsaturated local structure and the local galvanic couples between Si, B and Co increase the catalytic activity of Co78Si8B14 MG. The two degradation ways make Co78Si8B14 MG show wide applicability and good reusability in degrading dye wastewater.Cu46Zr44.5Al7.5Gd2 MG was found to degrade azo dye rapidly, which exhibits excellent catalytic activity with high stability over a multiple-cycling life. Azo dye can be degraded more easily by the Cu46Zr444.5Al7.5 Gd2, MG due to the lower thermal activation energy barrier of 17 kJ/mol. The degradation rate remains almost unchanged when the Cu64Zr44.5Al7.5 5Gd2 MG ribbons were reused for 18 times. The durability of Cu46Zr44.5Al75Gd2 MG will promote the practical application of MGs as functional materials.Fe₇₈Si₈B₁₄ MG was demonstrated as a new type of electrocatalyst to effectively and economically degrade an azo dye. Hydroxyl radicals ?·OH? generated by the reaction of water and dissolved oxygen electrocatalyzed on the surface of the Fe₇₈Si₈B₁₄ MGs with a high oxidation potential of ?2.8 V and were crucial for oxidatively degrading the azo dye. The electrochemical degradation rate ?U= 1V? is 12 times higher than that of the chemical degradation ?U = 0 V?. The degradation with Fe₇₈Si₈B₁₄ MG electrodes at 1 V exhibited the best performance owing to the high degradation efficiency, short reaction time, low specific energy and electrode mass consumption. In comparison to other typical electrodes, Fe₇₈Si₈B₁₄ MG electrodes exhibit a minimized degradation time, and the specific energy is 4-6 orders of magnitude lower than that of dimensionally stable anode, metal-like boron-doped diamond and carbon electrodes. Fe₇₈Si₈B₁₄ MG electrodes will promote the practical application of electrochemical technology.