Hydrothermal Synthesis Of BiOBr/XWO₄（X=Fe,Cu） Composite Photocatalysts And Their Photocatalytic Degradation Of Tetracycline

The treatment of antibiotic wastewater is a very serious problem all over the world.Doxycycline is an effective drug used to inhibit the diseases of upper respiratory tract infection and septicemia caused by Gram positive bacteria and negative bacilli,and it belongs to one of tetracycline drugs.However,excessive use of antibiotics can accelerate the spread of drug-resistant bacteria,reduce human immunity and pose a threat to the environment.Doxycycline has been detected in ground water and surface water,and the degradation of tetracycline by traditional wastewater treatment plants is not satisfactory.Increasing attention has focused on the pollution of doxycycline,and finding a solution for the doxycycline pollution is the most pressing need in this field.In this study,two kinds of BiOBr/XWO₄（X=Fe,Cu）composite photocatalysts were prepared to degrade several tetracycline.The main contents were divided into two parts:P-P BiOBr/FeWO₄ heterojunction was prepared by the solvothermal method.The crystalline structures,morphology,chemical composition,chemical bonding,energy band gap and photocatalytic properties of the samples were characterized by XRD,SEM,TEM,EDS,XPS,FT-IR and UV-Vis DRS.the morphology of BiOBr/FeWO₄ was composed completely of microspheres.The bandgaps of BiOBr,BiOBr/FeWO₄（1:1）,BiOBr/FeWO₄（2:1）,BiOBr/FeWO₄（4:1）and BiOBr/FeWO₄（8:1）were found to be 2.90 eV,2.73 eV,2.63 eV,2.46 eV and 2.57 eV,respectively.BiOBr/FeWO₄（4:1）degraded 90.4%of doxycycline in less than 1 h and after four cycles of degradation experiments,the photocatalytic doxycycline hydrochloride BiOBr/FeWO₄ photocatalyst still showed excellent sustained stability and excellent photocatalytic efficiency.The results indicated that FeWO₄ enhanced the light response range of BiOBr and accelerated the separation of the carriers photogenerated under visiblelight.P-N BiOBr/CuWO₄ heterojunction was prepared by the solvothermal method.By several different characterization techniques,it was found that the diameter of BiOBr/CuWO₄ hollow microspheres has changed from 1-2μm to 1-5μm.The degradation pathways of all the samples followed the pseudo-first-order kinetic model.The rate constants k were 0.0159 min^-1,0.0024 min^-1,0.0176 min^-1,0.0248 min^-1,0.0277 min^-1 and 0.0424 min^-1 for BiOBr,CuWO₄,BiOBr/CuWO₄（1:1）,BiOBr/CuWO₄（2:1）,BiOBr/CuWO₄（4:1）and BiOBr/CuWO₄（6:1）,respectively.The BiOBr/CuWO₄ composite photocatalysts with different molar mass ratios exhibited higher photocatalytic degradation efficiency of doxycycline.The composite photocatalyst leading to high degradation on doxycycline hydrochloride（DC）,tetracycline（TC）,oxytetracycline（OTC）and chlortetracycline hydrochloride（CTC）,and the degradation rate were 92.4%,93.7%,85.3%and 81.4%,respectively.It can be seen that the BiOBr/Cu WO₄（6:1）composite photocatalyst has high catalytic activity for all tetracycline antibiotics.