Rapid Liquid-phase Preparation And Properties Of The Micro-/Nano-Structural Iron-Rich Catalytic Degradation Materials

With the rapid development of modern industry and people's living standard,the species and quantity of toxic and bio-refractory organic pollutants contained in industrial wastewater are increasing constantly.Iron-rich materials used as heterogeneous catalysts for advanced oxidation processes?AOPs?can produce hydroxyl radicals??OH?,which can sufficiently and nonselectively oxidize these organic pollutants.Iron-rich materials can also be easily seperated and recycled without any secondary pollution.Out of economic considerations,the development of new growth technologies which are efficient,controllable,low cost,and suit-able for practical production of heterogeneous catalysts for AOPs is necessary.In this dissertation,iron alkoxide hierarchical structure and bismuth ferrite mi-cro/nano-particles were facilely synthesized by microwave-poloyl and micro-wave-hydrothermal processes,respectively.Fe₃O₄@C hollow-out frameworks with a large surface area were obtained by pyrolysis of iron alkoxide.The morphologies and crystal struc-ture of the micro/nano-structures were characterized via SEM,TEM,XRD,XPS,Raman,FTIR,and UV-Vis spectrum,etc.The relationships between the structure and growth process were investigated.In addition,the adsorption,?photo-?Fenton catalysis and visible-light ca-talysis properties of the as-prepared products were extensively studied.The dominant research content and discussion are as follows.?1?Iron alkoxide hierarchical structures were facilely synthesized by microwave-assisted polyol method.The influence of glycol?EG?-mediated processing parameters,includ-ing heating temperature,time,rate,stirring method and addition of ethanolamine?ETA?on the structure and morphology of iron alkoxide was investigated systemati-cally.The results obtained are as follows:1)The hierarchical 3D flowerlike structure was obtained at 180°?.Under similiar experimental conditions,the hierarchical structure changed from a 3D flower into a nanoflake,then a nanoparticle with the temperature increasing.The iron alkoxide existed as FeII-FeIII glycolate.2)With as-sistance of ETA,the iron alkoxide featured high crystallinity and can be assembled into a regular sheet morphology under stirring.?2?Fe₃O₄@C hollow-out frameworks with a low coercivity were obtained by annealing of iron alkoxide in an inert atmosphere.The effects of the crystal structure and morphol-ogy for the precursor on the Fe₃O₄@C hollow-out frameworks were studied.The re-sults obtained are as follows:The higher the crystallization degree of the precursor,the better the dimensional homogeneity of Fe₃O₄@C.The hollow Fe₃O₄@C frameworks had a high mechanical strength and the morphology remained intact under ultrasonic conditions.?3?Bismuth ferrite?BiFeO₃ and Bi₂Fe₄O₉? materials were quickly synthesized via micro-wave-assisted co-precipitation-hydrothermal method.A "core-shell aggregate" mech-anism was proposed to explain the growth of the BiFeO₃ micro-cube?BFO-MC?via a co-precipitation-hydrothermalmethod.Accordingtothemechanism,hexadecyltrimethylammonium bromide?CTAB?was employed as surfactants to adjust surface energy to suppress the growth and ripening of BiFeO₃ nanoparticles?BFO-NPs?.?4?The stability of iron alkoxide and its removal efficiency of organic dye from solution were investigated systematically.Owning to a large specific surface area,455.16 m²/g,and zero isopotential point,about 8.5,the iron alkoxide exhibited a strong adsorption?513 mg/g?for congo red?CR?.The Langmuir model and Webber-Morris kinetic equation were employed to explain the adsorption process.The adsorption mechanism,namely the ligand substitution and electrostatic adsorption along with FeII reduction,coordination and H-bond interaction,is tentatively proposed.Owning to a high ad-sorption capacity and FeII content,the degradation of iron alkoxide to anionic dyes congo red?CR?and methyl orange?MO?were stronger than rhodamine B?RhB?.?5?The magnetic properities,?photo-?Fenton catalytic and photo catalytic activity of the iron alkoxide,the Fe₃O₄ nanoclusters,the Fe₃O₄@C hollow-out frameworks and the BiFeO₃ nanoparticles were investigated.The results obtained are as follows:1)Alt-hough the 3D flower-like iron alkoxide showed a?photo-?Fenton catalytic activity,it was metastable and easily oxidized to FeOOH.2)Fe₃O₄@C hollow-out frameworks had the advantage of strongest oxidation resistance,minimum iron leaching and higher utilization rate of H₂O₂.3)BiFeO₃ exhibited a poor Fenton catalytic activity but an excellent visible light catalytic performance without the addition of H₂O₂.The photocatalytic degradation of RhB using BFO-NP was controlled mainly by the hy-droxyl radicals??OH?.The current work shows that the microwave-assisted liquid-phase technique is a low cost and facile approach for micro/nano-structural iron-rich materials.The growth of mi-cro/nano-structural materials can be controlled by the parameters of the growing process.The as-prepared iron-based micro/nano-materials have shown an important potential in the appli-cation of removal of organic dyes through Fenton catalysis and photocatalysis.