| Persistent endocrine disrupting chemicals(EDCs),such as bisphenol A(BPA),have gained considerable attention over the past decade as priority pollutants due to their continuous release in the water cycle and their suspected adverse effects on human health and wildlife.Numerous toxicological studies proved that BPA is hazardous to aquatic environment,even in low concentration(ng/L),along with alterations in the devlopment and physiology of living organisms.The BPA exhibits the hydrophobic and nondegradable properties,and the traditional wastewater treatment method is difficult to achieve its effective degradation.Semiconductor photocatalytic technology have attracted wide attention due to its great potential in degrading most of these bio-refractory organic pollutants without secondary pollution by using the visible-light as the excitation energy.Under visible-light irradiation,Ag3PO4 exhibits extremely higher photocatalytic efficiency for organics.However,there are some crucial difficulties in the practical applications of pure Ag3PO4,including the uncontrolled photocorrosion problem that occurs under light irradiation and the challenges of the suspended particulate catalyst collection in the photocatalytic separation process.According to the bottlenecks that the poor photostability of the visible light responsive photocatalyst Ag3PO4,this paper proposes an innovative composites construction strategy for Biochar-MFe2O4/Ag3PO4(M=Zn,Co).The magnetic biochar was prepared with the "one-pot" method in a controllable manner by using the pine pollen as templates and CoFe2O4(ZnFe2O4)as magnetic mediums.And then the in-situ precipitation method was used to prapare the Biochar-CoFe2O4/Ag3PO4 and Biochar-ZnFe2O4/Ag3PO4 composite materials.The photocatalytic properties of the Biochar-CoFe2O4/Ag3PO4 and Biochar-ZnFe2O4/Ag3PO4 were systematically investigated with BPA as the treatment object.On the basis of activity test characterization,the mechanism of the photocatalytic degradation of the BPA with these composites were revealed.The main contents and conclusions are as follows:1?Comparing with pure Ag3PO4,the composite materials display outperform catalytic performance(higher activity and super stability).While in Biochar-CoFe2O4/Ag3PO4(MB:Ag3PO4 =3:7)photocatalytic system,about 91.12%of BPA and 80.23%of TOC are removed within 60 min visible-light irradiation.Also,BPA is approximately decomposed completely(98.23%)by Biochar-ZnFe2O4/Ag3PO4(MB:Ag3PO4 =1:4)with the superme mineralization of 86.08%was achieved.In detailed,the degradation rate of BPA in Biochar-CoFe2O4/Ag3PO4 and Biochar-ZnFe2O4/Ag3PO4 photocatalytic system presented the highest value of 0.0341 min-1,0.0608 min-1,which is 4.9 and 9.4 times those of pure Ag3PO4,respectively.Meanwhile,Biochar-CoFe2O4/Ag3PO4 and Biochar-ZnFe2O4/Ag3PO4 exhibits excellent photocatalytic stability with the degradation efficiency(87.36%)and the rate of mineralization(69.73%)keeping at a high level after three-times recycling reactions,which is higher than that in the Ag3PO4 photocatalytic system(approximately 9.58%).2?The characterization of the Biochar-CoFe2O4/Ag3PO4 and Biochar-ZnFe2O4/Ag3PO4 composite photocatalyst were accomplished by means of SEM,HRTEM,BET and other characterization means.The results show that the introduction of the magnetic biochar(Biochar-ZnFe2O4)can significantly reduce the diameter and agglomeration of the Ag3PO4 in the composite photocatalyst and enlarge the surface area of composite.3?The characterization of the Biochar-CoFe2O4/Ag3PO4 and Biochar-ZnFe2O4/Ag3PO4 composite materials were accomplished by means of UV-vis,EIS and PL.The introduction of carrier(Biochar-ZnFe2O4 and Biochar-CoFe2O4)not only enhance the absorption range of light, but also decreased the rate of recombination of photogenerated electron-hole pairs,leading to a greatly improved photocatalytic performance of the composite photocatalyst.4?The results of ESR and free radical capture experiments demonstrate all the three scavengers inhibit the photodegradation,efficiency in various degrees,and the order of reactive species in Biochar-MFe2O4/Ag3PO4(M=Zn,Co)system is photogenerated holes(h+)>super-oxide radical(O2·-)>hydroxyl radical(·OH).Furthermore,a possible mechanism,direct hole oxidation,is illustrated for BPA degradation.5?The improved photocatalytic performance of the BBiochar-CoFe2O4/Ag3PO4 and Biochar-ZnFe2O4/Ag3PO4 composite photocatalyst is attributed to the better adsorption efficiency,the higher optical absorption property and the lower electron-hole recombination rate. |
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