Controllable Synthesis Of Iron-based Nanocomposites And Its Application In Treatment Of Organic Wastewater

The organic pollutants in the wastewater not only bring harm to animals,plants and human body,but also pose a great threat to the entire environmental ecosystem.Therefore,it is extremely urgent to efficiently treat organic pollutants in wastewater.Iron-based nanooxides are rich in nature and harmless to the environment,and have the characteristics of small size and quantum size of nanomaterials,which make them occupy an important position in the field of wastewater treatment.In this thesis,nano-hydroxyferric oxide??-FeOOH?and its composites with fusiform morphology were synthesized by solvothermal method combined with controlled hydrolysis method.They were applied to the adsorption and photocatalytic treatment of organic wastewater,and provided theoretical support for its application in wastewater treatment.The specific research contents are as follows:The?-FeOOH nanomaterials with fusiform morphology were synthesized by green and simple solvothermal method.The morphology and structure of the nanomaterials were investigated by a series of characterization methods.On this basis,in order to further understand the influencing factors of the synthesis process of the nanocrystals,the influence of the synthesis conditions on its morphology and structure was explored,and the synthesis mechanism was discussed.The results show that the specific reaction temperature has an important influence on the morphology of?-FeOOH.As the temperature increases,the morphology of the product changes from the initial long rod to the spindle and eventually becomes an irregular spherical shape;the proper proportion of glycerol and water molecules on the surface of the nucleus has a significant effect on the nucleation and growth of fusiform?-FeOOH nanocrystals.The organic dye wastewater was simulated by high concentration Congo red?CR?solution,and the synthesized fusiform nano-?-FeOOH material was applied to the adsorption of wastewater.The effects of?-FeOOH nanoparticles on the adsorption of CR under different adsorption conditions were investigated.The adsorption kinetics and adsorption isotherms of the adsorption process were fitted to explore the adsorption mechanism.The results show that the adsorption process depends on the amount of adsorbent,the pH of the solution,the reaction time and the initial dye concentration.The optimum amount of adsorbent is 0.035 g,the adsorption equilibrium time is 30 min,and it has a wide range of pH application?6-12?;the maximum adsorption capacity reaches 714.29 mg/g,which is much higher than most similar materials.The adsorption kinetic data is in good agreement with the pseudo second-order kinetic model;the adsorption process is consistent with the Langmuir and Freundlich adsorption isotherm models.The adsorption mechanism was also analyzed by means of FTIR,indicating that the adsorption process involves not only electrostatic interaction,but also ion exchange or functional group bonding.?-FeOOH can achieve 90%treatment even at a concentration of 1000 mg/L in CR wastewater.The Fe-Ti nanocomposites were synthesized by controlled hydrolysis method with fusiform nano-?-FeOOH as the precursor.The photocatalytic persulfate system was constructed by using the composite as catalyst.The performance of catalytic persulfate degradation of organics was studied under simulated sunlight.In addition,the mechanism of pollutant degradation was investigated by free radical trapping and FTIR experiments.The results show that the Fe-Ti nanocomposite catalyst is obtained by the combination of titanium oxide and?-FeOOH,and the response wavelength is extended to the visible region,which can make full use of the simulated solar source.The photocatalytic persulfate system constructed in this experiment can degrade RhB quickly and efficiently.When the addition amount of tetrabutyl titanate was 600?L during the synthesis,the photocatalytic performance of the Fe-Ti composite catalyst was the best.The optimum amount of oxidant potassium persulfate in the system is 1g/L,and the catalyst addition amount is 1 mM;the system has excellent photocatalytic degradation performance in a wide range of pH?2-7?.The catalyst shows good stability and recyclability through recycling experiments.The capture indicates that SO₄^·-,·OH,·O₂^-and h⁺are involved in the oxidative degradation of organic pollutants,among which SO₄^·-are the main reactive oxygen species of RhB degradation,while·OH,·O₂^-and h⁺plays an auxiliary role.Further studies have found that the photocatalytic persulfate system can be used not only for the removal of a single RhB dye,but also for a variety of organic substances?methylene blue,methyl orange,phenol and bisphenol A?.The results show that the photocatalytic persulfate system constructed in this paper can be an efficient catalytic oxidation technology for the treatment of refractory organic wastewater.