Preparation Of Perovskite-Based Heterojunction Photocatalysts And Study On Degradation Of Organic Wastewater

In recent years,more and more pollutants have been found in the water,especially residual antibiotics have slowly gathered and been enriched,which have not only gradually affected the normal growth of aquatic animals,plants and bacterial colonies,but also brought great risks and threats to human health.In order to practice the development concept of green environmental protection,this study developed perovskite-based heterojunction photocatalysts with excellent photocatalytic activity and stability,and combined it with heterogeneous photo-Fenton catalytic oxidation for the degradation of Ceftriaxone sodium（CRS）antibiotic wastewater.A series of x-SnS₂/LaFeO₃（x=5-50 wt.%）composites with different content ratios were prepared by sol-gel and hydrothermal method.XRD,FT-IR,XPS,SEM and other characterizations have proved that the SnS₂/LaFeO₃ heterostructure was successfully constructed.And the results of photoelectric properties have suggested that the construction of heterojunction was beneficial to the efficient transfer and separation of photo-generated charges.All as-prepared photocatalysts were used to degrade CRS in visible light irradiation（λ>420 nm）,and the results showed that all the SnS₂/LaFeO₃ composites exhibited higher photocatalytic activity than single LaFeO₃ and SnS₂.That could be attributed to the synergistic effect between heterojunction photocatalysis and interfacial Fenton-like reaction,which could not only promote electron transfer,but also improve the redox process of≡Fe（Ⅲ）/Fe（Ⅱ）and activation efficiency of H₂O₂,and further facilitate the generation and utilization of active substances（·OH and·O₂^-）.The optimal ratio of 20-SN/LFO heterojunction material was selected to conduct the degradation of CRS by single factor tests.After considering the cost,the optimal technological conditions were as follows:initial CRS concentration was 20 mg/L,catalyst dosage was 0.5 g/L,hydrogen peroxide dosage was 0.5 m L and pH value was 7,and the degradation efficiency of CRS reached 87.54%after reaction for 150 min.In addition,the removal rate of CRS could still remain above 85.00%after four consecutive reactions,which displayed the good chemical stability of 20-SN/LFO catalyst.Four kinds of x-Bi₂S₃/LaFeO₃（x=5-30 wt.%）heterojunction photocatalysts with different content ratios were successfully built by sol-gel and solvothermal method,and then were characterized.The photocatalytic properties of pure LaFeO₃,pure Bi₂S₃ and different Bi₂S₃/LaFeO₃composites were compared by photo-Fenton degradation experiments of CRS.The results showed that after the combination of Bi₂S₃ and LaFeO₃,the photocatalytic activity of all Bi₂S₃/LaFeO₃composites were significantly improved,which could be ascribed to the enhanced visible light absorption and improved photocarrier separation and migration performance after the formation of the heterojunctions.The 10-BS/LFO composite exhibited the best photocatalytic performance,and the CRS removal rate reached 92.25%after 150 min.The result of recycling experiments indicated that the 10-BS/LFO photocatalyst had no significant activity loss,displaying good reuse performance.Free radical capture experiments proved that·OH and h⁺were the main active substances during the catalytic CRS degradation process.Combining the result with the analysis of energy band structure,the mechanism of photo-Fenton degradation of CRS by Bi₂S₃/LaFeO₃ heterojunction photocatalyst was proposed.At the same time,the possible degradation pathway of Ceftriaxone sodium was explored,and toxicities of Ceftriaxone sodium and its intermediates were analyzed and predicted by using T.E.S.T.toxicity assessment software.This study provides a feasible method for the development of photo-Fenton composite catalyst with high catalytic activity for the efficient treatment of antibiotic wastewater under visible light,which has potential value and significance.