Synthesis And Photodegradation Performance Of BiOI/ZnO/rGO Composites

Recently,pesticides and antibiotics with harmful impacts on human health have become two major contaminants in water pollution due to their widespread use in agriculture and medical activities.To prevent the harmful effects of drugs such as pesticides and antibiotics,harmless disposal of wastewater before being discharged to the environment is necessary.Photocatalytic technology is a method to realize the mineralization degradation of pollutants by using light energy to drive the REDOX reaction of semiconductor catalysts.Among various semiconductor catalysts employed in environmental remediation,Zinc oxide（ZnO）is recognized as a promising catalytic material because of its advantages including low cost,eco-friendly,high photosensitivity,high thermal and chemical stability and high electron mobility.However,the application in visible light of ZnO is being limited because of its wide band gap energy and low quantum efficiency results of the fast photo–carrier recombination rate.In order to overcome these defects,the paper tried to introduce BiOI and graphene materials to modify ZnO.Firstly,ZnO was synthesized on graphene oxide（GO）carrier by hydrothermal method to prepare ZnO/rGO composites.The photodegradation efficiency of diethoate under ultraviolet light showed that the optimal ratio of rGO was 10 wt%.The optimal dosage of diethoate was0.5 g·L^-1 and the optimal initial concentration of diethoate was 5 mg·L^-1.Characterization of ZnO/rGO composites shows that the introduction of GO can not only increase the specific surface area of the composites which promotes the adsorption and transport of substrate and oxygen,but also inhibit the electron-hole recombination and improve the transport of carriers.On this condition,the photocatalytic performance of ZnO/rGO composite was the highest.The degradation efficiency of dimethoate reached 99%under UV light for 180 min,and the photodegradation rate and efficiency were 4 times and 1.5 times of that of pure ZnO,respectively.Secondly,BiOI/ZnO heterojunction were synthesized by one–step hydrothermal method.The photodegradation rate of metronidazole under visible light showed that the optimal specific gravity of BiOI was 10 wt%,the optimal dosage of the catalyst was 0.5 g·L^-1 and the optimal initial concentration of metronidazole was 20 mg·L^-1.Characterization of the BiOI/ZnO heterojunction showed that the formation of heterojunction could not only reduce the material band gap,but also delay the recombination of electron holes.In addition,the introduction of BiOI can improve the specific surface area of ZnO and promote the adsorption of degraded substrates.At the same time,BiOI/ZnO heterojunction showed the highest photocatalytic performance.The degradation efficiency of metronidazole under 180 min of visible light irradiation reached 94%,and the photodegradation rate was 2.6 times and 4.8 times that of ZnO and BiOI,respectively.Finally,BiOI/ZnO/rGO composites were constructed using GO as the carrier by loading the BiOI/ZnO heterojunction on it.The photodegradation rate of chloramphenicol under visible light showed that the optimal proportion of rGO was 5 wt%,the optimal dosage of chloramphenicol was 0.5 g·L^-1 and the optimal initial concentration of chloramphenicol was10 mg·L^-1.Characterization of the BiOI/ZnO/rGO composites showed that the introduction of rGO could not only improve the specific surface area of the BiOI/ZnO heterojunction,but also inhibit the recombination of charge carriers,thus achieving efficient charge transfer at the catalyst interface.At the same time,BiOI/ZnO/rGO composites showed the highest photocatalytic performance.The degradation efficiency of chloramphenicol by visible light irradiation for 180 min reached 90%,and the photodegradation rate was 8.1 times that of BiOI,2.0 times that of ZnO,and 1.8 times that of BiOI/ZnO.