| Wastewater with dyes is toxic to microorganisms and has poor biodegradability.It is difficult to be biodegraded rapidly and effectively.Photocatalysis is a technology which can degrade the refractory pollutants with high effection.It’s a feasible method to use photocatalytic technology to degrade dye wastewater,which have excellent reaction rate and whose reaction is not selective.It would be cleaner and not produce secondary pollution.There are many materials that can be used as photocatalysts.Finding the catalyst that is in response to visible light is the key to promote the practical application of this technology.g-C3N4 is one of the most widely materials in photocatalysis,but the photocarriers of g-C3N4 is easy to recombine,so it needs to be modified to improve its photocataloytic activity.The construction of Z-type heterojunctions is one of the most convenient and effective methods.The key to construct Z-type heterojunctions is to find materials with matching edge.The research contents of this project are as follows.Firstly,g-C3N4 and V2O5 were prepared by heat treatment,and the raw materials are melamine and ammonium respectively.After that,V2O5/g-C3N4 binary composite was prepared by hydrothermal method.The morphology,element distribution,crystal structure and optical properties of the material were observed by characterizationSecondly,the degradation of Rhodamine B(Rh B)was studied,and the degradation of Rh B by V2O5/g-C3N4 accorded with pseudo first-order kinetics.The degradation of RHB by binary composite is better than that by g-C3N4 and V2O5.The effects of doping ratio,p H value,consumption of catalyst and kinds of dyes on photocatalytic degradation were investigated.When the doping ratio is 1.5%,the degradation rate of Rh B is the best.With the decrease of p H,the photocatalysis efficiency of composite materials increases.When the catalyst dosage is 0.03 g,the photocatalytic effect is the best.In addition,the degradation of methylene blue(MB),methyl orange(MO)and malachite green(MG)was studied.It is found that the degradation rate of dyes can reach more than 90% in 150 min,when the binary materials degrade above dyes.It can be proved that the composite has universal applicability to dyes.Four cycle experiments of composite materials and the XRD pattern before and after material circulation show that the binary composite has good stability.The quenching experiment and the correlation calculation prove the construction of Z-type heterojunction.Finally,the life cycle assessment is carried out to evaluate the environment impact of the preparation,use and treatment of binary composite materials.The fuctional unit of LCA is to prepare 0.03 g photocatalytic material.The evaluation system is the whole process of preparation of the photocatalyst,degradation of 100 m L Rh B solution with concentration of 10 mg/L and the treatment of the photocatalyst.The results show that in the non-recycling or recycling scenario,the preparation phase has the greatest contribution to the environment impact of the whole material life cycle system.The environmental impact value of ecological toxicity and global warming potential of fresh water is large.Therefore,the material has a great impact on climate change and water health.In addition,PVP,electrical energy and photocatalyst have a greater impact on the environment.Low frequency ultrasound and other measures can be used to reduce the impact of environment.Recycling materials can reduce the environmental impact of the whole life cycles system,especially the global warming potential and ecological toxicity of freshwater sediment.Summarize the overall study,it can be judged that V2O5/g-C3N4 binary composite has good photocatalytic activity in the degradation of dyes,and the optimal conditions and rules of photolysis are obtained.Through the study of mechanism,stability and life cycle assessment,it provides a theoretical basis for achieving cleaner production and improving the environmental friendliness of the material. |
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