Preparation Of Bi-based Heterojunction Photocatalyst And Their Removal Of 17?-ethynylestradiol

When human is exposed to 17alpha-ethynylestradiol(EE2),it can cause a series of adverse effects including changes in reproductive behavior,decreased hormone levels,and changes in the second characteristics of men.As a hydrophobic organic pollutant,EE2 is ubiquitous in water,which is threatening the reproduction and development of animals and plants.Therefore,it is meaningful to find effective methods to remove EE2.In recent years,bismuth-based semiconductors have been widely synthesized and used as photocatalysts to remove organic pollutants due to their excellent optical properties.In this paper,two kinds of Bi2O3/Bi2O4 and AgI/BiOI/BiPO4 heterojunction photocatalysts were prepared by calcination and ion exchange methods,respectively.The phase,morphology,chemical state and optical properties of the materials were analyzed by XPS,XRD,PL and SEM,etc.The photodegradaion performance of the heterojunctions was studied through the degradation of EE2 under visible light.Meanwhile,the degradation mechanisms of EE2 over the heterojunction photocatalysts were discussed.The details are as follows:1.Bi2O3/Bi2O4 binary heterojunction photocatalyst was synthesized via the calcination.The optimum synthesis conditions were as follows:The mass ratio of NaBiO3/KOH was 2.5,the calcination time was 2 h,and the calcination temperature was 25?.The degradation efficiency of Bi2O3/Bi2O4 for EE2 could reach a maximum value of?100%in 12 min under the visible-light illumination,whose reaction rate constant was 6.57 times higher than commercial Bi2O3.The photocatalyst changed from Bi2O3/Bi2O4 heterostructure to Bi2O3/Bi2O2CO3 heterostructure after photocatalytic reaction and maintain the good photocatalytic performance.The possible charge transfer paths and degradation mechanisms of EE2 over the Bi2O3/Bi2O4 was deduced by trapping experiments and energy band theory.2.AgI/BiOI/BiPO4 ternary heterojunction photocatalyst was synthesized via the ion exchange method.The synthesis was accomplished in two steps:First,BiOI was synthesized,then AgI/BiOI/BiPO4 was synthesized by ion exchange using BiOI as the template.The optimum synthesisc conditions of BiOI were as follows:KI aqueous solution was dripped into DMF solution of Bi(NO3)3·5H2O and stirred for 4 hours.The optimum conditions for the synthesis of AgI/BiOI/BiPO4 were as follows:0.5 g BiOl,the mole ratio of BiOI:AgNO3:NaH2PO4·2H2O was 2:2:2.The degradation efficiency of Agl/BiOI/BiPO4 for EE2 could reach a maximum value of?100%in 8 min under the visible-light illumination,whose reaction rate constant was 11.54,5.55,2.46,1.71 of that of AgI,BiOI,AgI/BiOI and AgI/BiPO4,respectively.Various heterojunctions(n-p AgI/BiOI,n-n AgI/BiPO4,p-n BiOI/BiPO4,n-p-n AgI/BiOI/BiPO4)coexisting in the system have flexible and diverse charge transfer mechanisms,which greatly improved their photocatalytic activity.