| Currently, the pollution of antiobiotics to water environment seriously threatens the ecosystem and human health and livestock wastewater is the main source. Tetracycline, as one of the most common antibiotics, has gained wide attention in recent years. Because of the existence of limitations in conventional treatment approaches, bioflocculants are used to treat tetracycline in livestock wastewater with high efficiency and non-second pollution in this thesis. In order to overcome defects of traditional adsorbents for difficulty in separation after being used in water, one kind of new magnetic bioflocculant is exploited to treat tetracycline effectively and without second pollution, which could provide technical support for the practical application of bioflocculants.The analysis of influences of each factor on removal efficiency shows that under the condition of 60 mg/L of bioflocculants MFX, 90 μL of coagulant aids(10% Ca Cl2), p H 8.0, 50 min of adsorption time, and 80 μg/L of initial tetracycline concentration, the removal efficiency of bioflocculants to tetracycline reaches the highest at 71.68%. The removal efficiency optimized by response surface(RSM) shows that the optimal removal efficiency of bioflocculants to tetracycline reaches 81.43% under the condition of 68.40 mg/L of bioflocculants MFX, 82 μL of coagulant aids, p H 8.5, 50 min of adsorption time, and 76 μg/L of initial tetracycline concentration.Thermodynamics analysis result shows both Langmuir and Freundlich adsorption isotherm model could describe the adsorption process. The adsorption process is exothermic reaction and adsorption efficiency is high. Dubinin-Radush Lkevich adsorption isotherm model shows that the adsorption is caused by chemical ion exchange. Kinetics analysis shows that pseudo-second order kinetics model could describe the adsorption process, which belongs to chemical adsorption process. The characterization of SEM, FTIR, Zeta potential and 3D-EEM shows that the porous structure of MFX is packed closely after absorbing tetracycline and hydroxyl is the main action site during the adsorption process in which adsorption bridging, sweeping flocculation and chemical adsorption are the main action.The synthetic magnetic powder is maghemite(γ-Fe2O3). It binds with bioflocculant MFX to form magnetic bioflocculant. It is one kind of dark brown powdery substance with stronger magnetism which possesses porous structure and bigger specific surface area. Under the condition of 16 mg of magnetic bioflocculants, 90 μL of coagulant aids, p H 6.0, and 30 min of adsorption time, the removal efficiency of magnetic bioflocculants to 80 μg/L of tetracycline reaches the highest at 81.82%, and the removal efficiency is high. The adsorption mechanism analysis by XRD, SEM, FTIR and Zeta potential shows magnetic bioflocculant has good adsorption effect for tetracycline. Tetracycline sufficiently occupies adsorption sites of magnetic bioflocculant after being adsorbed. The main type of adsorption reaction is with chemical adsorption. Hydroxyl and carboxyl are main functional groups, and the increase of adsorption sites may be the main reason for its good removal efficiency. |
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