Design And Performance Study Of Sulfide Composite Bismuth Tantalate Photocatalytic Material

Industrial development has introduced various water pollution.Semiconductor photocatalysis is a potential water purification method,because of its low cost,high efficiency and environmental friendliness.Bismuth tantalate(Bi₃TaO₇)has stable chemical properties,but the rapid recombination of photogenerated electrons and holes leads to its low utilization efficiency of visible light.On the other hand,metal sulfides usually have strong visible light response,but light corrosion is easy to occur in aqueous solution.As we all know,construction of Z-scheme heterojunction can effectively inhibit the recombination of photo-generated electrons and holes,which is an effective method to improve the efficiency of photogenerated charges transfer.In this paper,direct Z-scheme photocatalysts were successfully constructed based on Bi₃TaO₇ and metal sulfides,to improve and the photocatalytic performance of under visible light.The main research contents are as follows:(1)Direct Z-scheme photocatalyst Bi₃TaO₇/Bi₂S₃/SnS₂ was successfully synthesized by hydrothermal method.The catalyst exhibited different degradation activities for levofloxacin(LVFX),chromium(VI)and tetracycline hydrochloride(TC)under visible light.Compared with the pure sample,the apparent rate constants of Cr(VI)and TC degradation by the ternary composite catalyst were increased by 23 times,7 times,18 times,and 40 times,8 times,18times,respectively.Meantime,the degradation activity of the composite catalyst for LVFX enhanced with the increase of the ratio of Bi₂S₃ and SnS₂,but the highest degradation rate was only 22.1%.(2)The Z-scheme catalyst Bi₃TaO₇/CdS was synthesized by in-situ growth method.Compared to pure sample,the composites exhibited better degradation activity for CIP and LVFX under 30 min and 40 min visible light irradiation.The degradation was 76.5%and 85.1%,respectively.Meanwhile,the best sample BCS-2 also exhibited better stability and recyclability than pure CdS.The degradation efficiency of BCS-2 on CIP was still 75.7%after four cycles.The degradation decreased to 29%by CdS due to the photo corrosion.LC-MS anayla indicated that CIP was finally converted into small molecule substances such as CO₂.(3)The novel Z-scheme heterojunction with excellent photocatalytic performance was successfully constructed by in-situ growth of X_0.5Cd_0.5S(X=Zn?Mn)on the surface of Bi₃TaO₇.Photocatalyst BZCS-2 and BMCS-3 had the best degradation efficiency for LVFX under visible light irradiation,and the photocatalytic activity within 40 min were 85.8%and 89.4%.The enhanced photocatalytic performance can be explained as follow:Bi₃TaO₇ was compounded with X_0.5Cd_0.5S(X=Zn?Mn)to form the direct Z-scheme heterojunction,which improved the utilization efficiency of photogenerated electron-holes.Capture experiments suggested that holes,superoxide radicals and hydroxyl radicals degrade LVFX together.The final mineralized products were CO₂,H₂O,etc.Compared with the photocatalytic properties of the four composites,it is found that after the composite of Bi₃TaO₇ and Mn_0.5Cd_0.5S to form Z-scheme heterojunction provides more active sites and improves the utilization efficiency of photogenerated electrons and holes,which makes Bi₃TaO₇/Mn_0.5Cd_0.5S-3 show more excellent photocatalytic properties.