Removal Of Tetracycline From Sewage By Bismuth Tungstate Modified Magnetic Bentonite

Because tetracycline is used after entering the environment,resulting in pollution and even harm to human health.Tetracycline itself has high water solubility and stability,can exist in water for a long time,the problem of tetracycline in water has been paid attention to.Photocatalytic removal of tetracycline from water is expected to achieve good results,and the preparation of photocatalytic materials and the factors affecting the removal of tetracycline are worth further discussion.In this paper,bentonite was used as the base material to prepare BM and Bi₂WO₆/BM materials with two functions of adsorption and photocatalysis for the removal of tetracycline in wastewater.In this study,magnetic CoFe₂O₄ material was prepared,and bentonite and CoFe₂O₄were combined to prepare BM with both adsorption and photocatalytic properties.In the preparation process,the preparation conditions were optimized,and the prepared BM was analyzed and tested by XRD,SEM,UV-Vis,etc.,to characterize the BM.The results showed that the optimal stirring temperature was 70?and the ratio of bentonite to CoFe₂O₄was 1:1.5.It was confirmed by characterization that the two compounds were successfully combined,and the degradation efficiency of tetracycline with BM for 3 h was 72.0%.The performance of the prepared BM was studied,including the effects of p H in water,concentration of tetracycline,dosage of catalyst and the presence of coexisting ions on the degradation of tetracycline.The optimal removal conditions were p H 9,tetracycline concentration 10mg/L and catalyst concentration 0.05 g/L.The influence of coexisting ions in water is as follows:the effect of Cl^-on the removal of tetracycline depends on its concentration,the effect of NO₃^-can be ignored,and SO₄^2-and ammonia nitrogen inhibit the degradation process.·O₂,H⁺and·OH played a major role in the degradation process of free radicals.After six cycles,the removal efficiency of tetracycline by BM decreased by 8.0%.When the actual water sample was used as the research system,the tetracycline removal rate was 60.0%after 3 h of reaction,which was due to the fact that other organic matter in the actual water body was decomposed by BM.Bi₂WO₆/BM was prepared by loading Bi₂WO₆ on the basis of BM.During the preparation process,the best tetracycline removal effect was obtained when the optimal composite ratio was 3:1,and the removal rate reached 92.0%.The above characterization of the material confirmed that the degradation experiment was conducted after the successful composite of the material.The properties of the prepared Bi₂WO₆/BM were studied.The p H,tetracycline concentration,Bi₂WO₆/BM dosage and coexisting ions in water were taken as the influencing factors.When the p H was 11,the concentration of tetracycline was 10 mg/L,and the concentration of catalyst was 0.05 g/L,the removal rate of tetracycline reached92.0%.When the concentration of Cl^-was 15 mmol/L,the degradation efficiency of tetracycline was generally improved,while the removal of tetracycline was inhibited at other concentrations.The presence of SO₄^2-and ammonia nitrogen can also inhibit the degradation of tetracycline,while NO₃^-has no obvious effect on the experimental results.Bi₂WO₆/BM showed good stability,and the degradation groups were H+,·OH and·O₂.The actual water sample removal and degradation efficiency decreased by 4.7%within 3 h.Considering the complexity of the actual water sample,the change of COD concentration was taken as the experimental reference to explain the reason for the decline of tetracycline degradation efficiency:the prepared Bi₂WO₆/BM was not completely used to remove tetracycline in the water body,but was used to remove other organic matter existing in the actual water sample.