| Phosphorus is one of the main nutrient elements in the water. When the phosphoruscontent in water is excess, it will cause a series of serious environmental problems. Forexample, excessive amounts of phosphorus can lead to rapid growth of algae and plankton,and thus the oxygen content and light transmittance in the water will decrease, water qualitywill deteriorate, which may result in the massive death of aquatic life. What’s more, the badenvironment may do harm to people’s health and bring them economic losses. Therefore, toremove the phosphate in the water has become one of the important task of environmentalresearch. At present, many methods are used to remove phosphorus in the water, adsorptionmethod has been widely used because of its unique advantages. We all know that a perfectadsorbent is the key to the application of adsorption method. Compared with ordinaryadsorbent, magnetic rare earth adsorptive materials have many advantages, such as goodadsorption performance, rapid adsorption rate, large absorption capacity, reclaim and reuse. Inthis thesis, we synthesized two kinds of magnetic rare earth absorbents (Fe3O4@Y(OH)CO3and Fe3O4@CeO2·nH2O) by solution and solvothermal method, respectively. Meantime, avariety of modern analysis instruments, such as scanning electron microscopy (SEM),transmission electron microscopy (TEM), energy-dispersive X-ray spectrum (EDX), PowderX-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetryand differential analyses (TG/DTG), vibrating sample magnetometer (VSM) and are used tocharacterize their morphologies, structures, elemental composition, surface property, thermalstability and magnetism. We studied their adsorption dynamics and thermodynamics,investigated their influence factors such as pH value, initial concentration, adsorptive timeand temperature on the adsorption of phosphate, and discussed regeneration, recycle of theadsorption materials and adsorption mechanism.(1) We prepared Fe3O4@Y(OH)CO3adsorption material with core-shell structure usinga solution method. The surface of the particles is rough and the particle size is about220nmand the shell is about20nm. The maximum adsorption capacity is62.527mg/g. Theadsorption isotherm accorded with Langmuir model. Its correlation coefficient is0.9959. Itsadsorption kinetics equation can be well-fitted by the pseudo-second-order rate model and thecorrelation coefficient is greater than0.99. The adsorption reaction is an endothermic andentropy increase spontaneous process. The adsorption mechanism belongs to single molecularlayer chemisorption. (2) We prepared Fe3O4@CeO2·nH2O adsorption material by a solvothermal method. Thesurface of the particles is rough and the particle size is about210nm. The maximumadsorption capacity is9.2512mg/g. The Langmuir model fitted with the experiment data welland the correlation coefficient is0.9987. The adsorption kinetics followed thepseudo-second-order rate equation and the correlation coefficient is greater than0.99. Theadsorption reaction is an endothermic and entropy increase spontaneous process. Theadsorption mechanism belongs to monolayer physics adsorption.(3) The adsorbent can regenerate in0.25mol/L NaOH solution. The adsorbent can bereused for five times and the adsorption capacity slightly decreased after cycling five times.(4) The magnetic separation process may be finished within two miniutes, convenientlyand speedily.In this thesis, two kinds of magnetic rare earth adsorption materials were successfullysynthesized by using different methods. They not only showed good adsorption performance,but also can realize the fast magnetic separation. Thus, these magnetic rare earth adsorptionmaterials will have a great application potential. |
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