Adsorption-photocatalysis Synergy Effect With Modified Bi₂WO₆ In The Degradation Of Trace Antibiotics

In recent years,with the continuous development of social economy,the production of tetracycline antibiotics has been increasing progressively year by year,and the accumulation of tetracycline in the environment and its impact on human health have gradually attracted people’s attention.A series of environmental problems can not be underestimated since they are difficult to be degraded and are highly enriched in the environment.Currently,photocatalysis is a newly-developing technology among the field of green environmental protection,which has the advantages of high efficiency,no secondary pollution and utilizing solar energy.Nevertheless,in terms of the low concentration tetracycline polluted water,this technology notwithstanding has the disadvantage of poor adsorption performance,which leads to the low efficiency of photocatalytic oxidation.As a consequence,how to improve the adsorption and photocatalytic properties of photocatalysts has gradually become the priorities and objectives to researchers.In the meantime,it is still indispensable to further study how to reduce the wastage of catalyst and enhance the photocatalytic performance of the reactor in the practical water pollution treatment.On account of our previous research,this thesis took bismuth tungstate（Bi₂WO₆）catalysts as the targeted contaminant to explore the change of adsorption performance of Bi₂WO₆ catalysts which modified by surfactant,and optimate their preparation conditions.The adsorption and photocatalytic performance parameters of the modified Bi₂WO₆ catalysts were investigated with light concentration tetracycline polluted water as the objective.The mechanism of adsorption-photocatalysis synergistic effect with modified Bi₂WO₆ was analyzed in the degradation of trace antibiotics.The catalysts were loaded with the polyurethane sponge carrier,in order to investigate their effect operating in the continuous flow photocatalytic reactor,which provided guidance parameters for the application and recovery of powder catalyst.The main results were as follows:（1）The optimization of modified Bi₂WO₆ preparation method:A series of modified Bi₂WO₆ catalysts were prepared by solvothermal method on the basis of our preceding research.The optimal preparation conditions were raised through the analysis of adsorption experiment consequences and various characterization results:SDS（1.30wt%）,solvothermal time of 16h,and reaction temperature of 180℃.The catalyst（BS1.3）was confirmed that it possessed the best morphology,adsorption and photocatalytic performance which was prepared by the above method,and the adsorption efficiency of tetracycline that could be stabilized up to 83.81%within60min.（2）Research in the characteristics of tetracycline adsorbent process and adsorption-photocatalysis synergy mechanism of BS1.3 catalyst:The experimental results showed that the adsorption effect was optimal when the p H was 7.0 and the catalyst dosage was 1.00g/L.The adsorption isotherm was consistent with the Langmuir model,representing that it belonged to the monolayer adsorption with strong selectivity.The results of adsorption thermodynamics and kinetics indicated that the adsorption of tetracycline on BS1.3 was a spontaneous physico-chemical adsorption process.When the adsorption reaction achieved plenitude,h⁺,·O₂^-and·OH were active groups of photocatalytic degradation which degraded pollutants under light irradiation,and 97.30%of 20.00mg/L tetracycline could be removed within 80min.It was concluded that the adsorption-photocatalysis synergy effect of BS1.3 catalyst was enormously improved at the tetracycline removal.（3）Immobilization of BS1.3 material and its operation effect in the reactor:PVB was used as immobilized agent to prepare BS1.3/sponge catalyst for reducing the wastage of powdered catalyst and possess superior recycling.The loading rate of the composite catalyst was 51.72%,and the adsorption rate of tetracycline was about 60%.Besides,BS1.3/sponge catalyst had good performance in the photocatalytic degradation whose removal rate was 95.91%within 110min.The concentration of pollutants in the influent was set at 800.00μg/L for the sake of exploring the operation effect of the immobilized catalyst in the continuous flow reactor,and the optimal operation conditions were determined as follows:the amount of material was 0.60 g/L,light intensity was set to 140000 lux,illumination condition was 2 h intervals,HRT was 6 h.Under these circumstances,the supported catalyst removed trace tetracyclines by 96.81%,and still maintained a higher removal rate after running for12 days.