| Bisphenol A?BPA?is one of the representative endocrine disruptor chemicals?ECDs?.Due to the estrogen-like effects,its wide usage has caused serious environmental pollution problems.As an emerging advanced oxidation process?AOP?,photocatalysis technology has attracted extensive attention because of its green character,high efficiency,no secondary pollution and wide application range.Therefore,this study aimed to synthesize a series of Zn1-xAg2xO/rGO photocatalysts to achieve the efficient degradation of BPA under visible light irradiation.Zn1-xAg2xO catalysts were firstly synthesized by a microwave-assisted method in this study.The synthetic conditions were optimized through the photocatalytic degradation of BPA.The optimal doping molar ratio was 0.05?Ag:Zn?,when the optimal microwave temperature was 180?with a reaction time of 30 min.The BPA removal rate of Zn0.975Ag0.05O reached 90%.The effects of Ag+doping on the crystallinity,structure and specific surface area of the catalyst were characterized by X-ray diffraction?XRD?,X-ray photoelectron spectroscopy?XPS?,Fourier transform-infrared spectra?FTIR?,Brunauer-Emmet-Teller?BET?,UV–vis diffuse reflectance spectrum?UV-Vis DRS?,etc.It turned out that Zn1-xAg2xO was mesoporous materials composed of Zn,Ag and O,where Ag2O exsisted in the catalyst.With the increase of doping ratio,the amount of Ag2O increased.Zn0.975Ag0.05O showed the strongest visible light response among the Zn1-xAg2xO catalysts.The consecutive experiment and dissolution of metal ions showed the bad stability of the Zn0.975Ag0.05O catalyst.In order to enhance the stability of Zn0.975Ag0.05O,a series of Zn0.975Ag0.05O/reduced graphene oxide(Zn0.975Ag0.05O/rGO)composite catalysts were then synthesized by the microwave-assisted method.The degradation performance of BPA and stability of the composite were successively investigated.When the loading ratio was optimized as 3.0 wt%,the BPA removal rate of the composite was 80%.The crystallinity,surface morphology,compositions and optical property of the composite were characterized by XRD,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,XPS,FTIR,BET and UV-Vis DRS.The results showed that Zn0.975Ag0.05O/rGO were mesoporous materials with responses in the visible-light region,when GO was reduced to rGO in the microwave hydrothermal reactions.The specific surface area increased significantly from 10.69m2·g-11 to 16.72 m2·g-1 with the addition of rGO.The stability of the composite was significantly improved and the dissolution of Ag+was markedly decreased in the consecutive experiment.Afterwards,the reaction conditions of BPA photodegradation were optimized in succession.The BPA removal rate of Zn0.975Ag0.05O/rGO exhibited no significant changes at a pH of 4-10,indicating the excellent pH adaptability of the composite.The reaction kinetic models of BPA degradation were proved to be in agreement with the pseudo-first-order reaction kinetics.Trapping experiments,electron paramagnetic resonance?EPR?and photoluminescence?PL?tests were used to identify the major reactive oxygen species?ROS?of the photocatalytic system.It turned out that?OH and h+were mainly responsible for the BPA decomposition.The doping of Ag+into ZnO significantly reduced the bandgap of the catalyst,and the addition of rGO effectively inhibited the recombination of photogenerated electron-hole?e-/h+?pairs.The degradation pathways of BPA were detected and analyzed by High performance liquid chromatography tandem mass spectrometry?HPLC-MS/MS?and density functional theory calculation?Mulliken population and Fukui function analyses?.The BPA degradation mechanism by Zn0.975Ag0.05O/rGO under visible light irradiation was proposed accordingly. |
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