Preparation And Decolorization Properties Of CoFe₂O₄/C And TiO₂/CoFe₂O₄ With Different Morphologies

Nowadays,water pollution is becoming a major challenge faced by all human beings.Among those technologies,adsorption and photocatalysis have received more attention due to many advantages such as high-speed,high efficiency,and simple operation process,and a variety of adsorbents and catalysts have been researched and used extensively.In recent years,based on the concept of resources circulation and reuse,natural organism materials with low cost,extensive sources,high carbon content and high regeneration ability have captured the attention of many researchers on preparing activated charcoal.Meanwhile,TiO₂ has been widely studied as a photocatalyst because of its robust chemical stability,nontoxicity and cost-effective.However,it is difficult to fully remove the actived carbon or TiO₂,which may result in recycling issue and secondary pollution.One of the effective ways is to endow the materials magnetic properties through combining component with magnetic component,which can realize both efficient catalytic performance and magnetic separation.Cobalt ferrite?CoFe₂O₄?,which exhibits high saturation magnetization and good chemical stability,has been widely used as magnetic materials widely.Introduction of CoFe₂O₄ to carbon and TiO₂ can enhance the decolorization of dyes.Therefore,the preparation of CoFe₂O₄/C adsorbents and TiO₂/CoFe₂O₄ catalyst is of great considerable realistic significance in the wastewater treatment industry.The thesis mainly focuses on preparation of CoFe₂O₄/C and CoFe₂O₄/graphene-like carbons?CoFe₂O₄/LGC?materials by using template-assisted solvothermal method under the alkali-free condition.Based on it,TiO₂/CoFe₂O₄ composites with different morphologies were prepared by sol-gel method.The results show that the materials have effective decolorization performance and magnetic separation.This method possesses the advantages of simplicality,high efficiency,cost-effective,green and resource-rich.The thesis consists of three parts as follows:Part I: Preparations of CoFe₂O₄/C and CoFe₂O₄ via defatted cotton template-assisted solvothermal method and decolorization performance.A novel template-assisted solvothermal method was used to prepare CoFe₂O₄/C nanomaterial by using defatted cotton?DC?as the template and carbon sources and Fe?NO3?3?9H2O and Co?NO3?2?6H2O as Fe and Co sources without any other alkali additives.The prepared samples were characterized by XRD,FT-IR,TEM and SEM.The influences of the solvent species?H2O and EtOH?,solvothermal reaction temperature,time,and the content of defatted cotton in the composites on the saturation magnetization were investigated.The adsorption activities of the samples were also studied using the adsorption experiment of methylene blue as the model.The low-temperature activate treatment was applied to treat the sample which was prepared under the best preparation conditions,the adsorption activities of the low-temperature activate samples were also studied.The results indicate that the adsorption activities of fibrous CoFe₂O₄/C nanocomposite increase with rising reaction temperature,prolonging reaction time and increasing the DC content.The low-temperature activated samples exhibit excellent methylene blue?MB?decoloration capability,and can be separated easily under applied magnetic field.Therefore,CoFe₂O₄/C composite can be used as a potential adsorbent for the removal of MB from wastewater.Likewise,the novel template-assisted solvothermal method was used to prepare CoFe₂O₄(CF_fiber)nanomaterials.The as-synthesized samples were characterized by XRD,TG,TEM and SEM.The degradation of MB was used as the model reaction to investigate the effect of solvent types,calcination temperature and calcination time on photocatalytic activity of CF_fiber nanomaterials.The results indicate that the as-prepared CF_fiber shows hollow fibers structure and its saturation magnetic intensity?78 emu/g?is higher than the value of theoretical of CoFe₂O₄?72 emu/g?.The degradation efficiency of MB solution reaches 60 % on the sample CF_fiber when radiation time is 150 min under 300 W mercury lamp.MB degradation on CF_fiber follows pseudo-first-order kinetics model.In addition,the formation process of hollow fibers CF_fiber was investigated.Part II: Preparation CoFe₂O₄/LGC and CoFe₂O₄ via pomelo peel template-assisted solvothermal method and decolorization performance.Compared with defatted cotton,discarding pomelo peel?PP?would not only cause environmental pollution but also cause great waste.Based on part I,the CoFe₂O₄/LGC composites were prepared by using PP as the template via one-step template-assisted solvothermal method.The influences of solvent kinds,solvothermal reaction temperature,time and the content of PP in the composites on the saturation magnetization and adsorption activities were investigated.Response surface methodology design was used to design and evaluate the experiment.The low-temperature activate treatment was applied to treat the sample which was prepared under the optimal conditions,and the adsorption activities were also studied.The results show that CoFe₂O₄/LGC nanocomposites are nanosized and made of multilayer nanosheets.The adsorption study shows that the low-temperature activate samples exhibit excellent adsorption capacity for MB with adsorption capacity 28 mg/g,and can be separated easily under applied magnetic field.The adsorption follows pseudo-second-order kinetics model and Langmuir isotherm models.Similarly,the novel PP template-assisted solvothermal method was used to prepare CoFe₂O₄?CFsheet?nanomaterial.The degradation of MB was used as the model reaction to investigate the effect of solvent kinds,calcination temperature and calcination time on the photocatalytic activity of the as-prepared samples.The results indicate that the as-prepared CFsheet materials are consist of multilayer nanosheets.The CFsheet,which was prepared at the conditions inculding EtOH solvent,650 ? calcination temperature,and 1 h calcination time,exhibits 80 % decolorizing efficiency of MB solution when radiation time was 150 min under 300 W mercury lamp.MB degradation follows pseudo-first-order kinetics model.Part III: Preparations of TiO₂/CF_fiber hollow fibers and TiO₂/CFsheet nanosheets magnetic composites and photocatalysis performance.Based on the successful preparation of hollow fibers CF_fiber,the TiO₂/CF_fiber composites with core-shell structure were synthesized via sol-gel method by using CoFe₂O₄ as the core.The as-prepared samples were characterized by XRD,SEM,VSM and UV-Vis.The degradation of MB was chosen as the model reaction to investigate the effect of calcination temperature,calcination time and the content of CoFe₂O₄ on photocatalytic activity of the TiO₂/CF_fiber materials.XRD result indicates that the composite is composed of anatase-TiO₂ and spinel-type CoFe₂O₄.SEM result shows that the as-prepared core-shell TiO₂/CF_fiber composites have fibrous structure.VSM datas certify that Ms of TiO₂/CF_fiber composites is remarkably lower than that of CoFe₂O₄,but the TiO₂/CF_fiber composites can be separated rapidly under applied magnetic field.Compared with TiO₂,TiO₂/CF_fiber composites have large absorption on UV-Vis area.The pthotocatalytic effect of TiO₂/CF_fiber compound materials is superior to the pure TiO₂ and CoFe₂O₄.Similar to the previous parts,based on the successful preparation of CFsheet nanosheets,the TiO₂/CFsheet composites with core-shell structure were prepared through sol-gel method by using CFsheet as the core.SEM result indicates that as-prepared core-shell TiO₂/CFsheet composites have sheets structure.VSM results indicate Ms of TiO₂/CFsheet composite is remarkably lower than that of CFsheet,but the TiO₂/CFsheet composite can be separated rapidly under applied magnetic field.Photocatalytic experimental results show that the composites also have superior catalytic effect.The TiO₂/CFsheet,prepared at the conditions of 350 ? calcination temperature,2 h calcination time,and 30 % CFsheet,delivers 99 % decolorizing efficiency of MB solution when radiation time was 30 min under 300 W mercury lamp.MB degradation follows pseudo-first-order kinetics model.