Synthesis Based On LDH And Nb₂O₅ Materials And Their Application In Dye Removal

With the development of industry,a large amount of printing and dyeing wastewater is discharged into rivers,which has caused damage to the ecological environment and the health of people,seriously.The simple and effective adsorption method and the green environmental photocatalytic degradation method are two commonly used methods in the current printing and dyeing wastewater treatment technology.Layered double hydroxides?LDHs?can be used as adsorbents to adsorb dye molecules onto the surface or between layers to achieve removal.Nb₂O₅ is an n-type semiconductor with non-toxicity,long-term stability and corrosion resistance.It can be used as a photocatalyst to degrade dyes.In this paper,LDHs and Nb₂O₅are used as the main material to control the synthesis of new materials,and to study the effect and mechanism of the dye removal.Firstly,ZnAl-LDHs with different morphologies and sizes was synthesized by the method of urea hydrolysis with water-n-butanol mixed solution as solvent.From the SEM images,it was found that when V?water?/V?n-butanol?=3 or 0.3,the synthesized LDHs presented the“3D silk flowers”morphology?ZnAl-LDH-3?or the morphology of“sedimentary rocks”?ZnAl-LDH-0.3?.By studying the adsorption properties of the calcined product,it was found that ZnAl-LDO-3 shows better adsorption properties for the anion dye because of the larger specific surface area.After adsorption kinetics and Thermodynamics Simulation,it was found that its adsorption process is single layer chemisorption.With the increase of the dye concentration from 10 mg/L to 400 mg/L,the maximum adsorption amounts of Congo Red,methyl orange,and reactive red anionic dyes were:1540 mg/g?2.21mmol/g?,1153 mg/g?3.52 mmol/g?,and 390 mg/g?0.63 mmol/g?.Through mechanism studies,ZnAl-LDO-3 was found to adsorb dye molecules mostly on its surface.Secondly,the magnetic composites of Fe₃O₄/ZnAl-LDH and CoFe₂O₄/ZnAl-LDH were synthesized in pure water by using two kinds of magnetic nuclei with Fe₃O₄ and CoFe₂O₄.Through XRD,SEM and FT-IR characterization methods,it was confirmed that the magnetic core and LDH compound together.The Fe₃O₄/ZnAl-LDO and CoFe₂O₄/ZnAl-LDO adsorbents were prepared after calcination.Their adsorption properties for Acid Orange II?AOII?,Methyl Orange?MO?and Congo Red?CR?were studied,It was found that the CoFe₂O₄/ZnAl-LDO has the best removal effect.By studying the adsorption performance,it was found that the quasi-second-order kinetics model and the Langmuir isotherm model can be used to indicate that the adsorption process was a monolayer chemical adsorption.With the increase of dyes concentration from 10 mg/L to 300 mg/L,the maximum adsorption capacities of CoFe₂O₄/ZnAl-LDO were 276 mg/g for acid orange II,281 mg/g for methyl orange,and 452 mg/g for congo red,respectively.Finally,Fe₃O₄ and Co Fe₂O₄ are combined with Nb₂O₅ by hydrothermal method.The SEM,XRD,FT-IR analysis revealed that magnetic composites Fe₃O₄@SiO₂/Nb₂O₅ and CoFe₂O₄/Nb₂O₅ were prepared and the spherical Nb₂O₅ was on the surface of the magnetic core.The two composite materials can degrade Rhodamine B under the simulated sunlight.In comparison,the photocatalytic effect of CoFe₂O₄/Nb₂O₅ was more significant,and the Rhodamine B can be completely degraded after 9h.