Degradation Of Pollutants By Catalytic Oxidation And Reduction Technologies Based On Bio-Pd/C And Bio-Pd-Ag/rGO

Industrial wastewater contains a variety of toxic organic pollutants,which are discharged into the surface and groundwater through textile,plastic,leather,paper and pharmaceutical industrial processes.Long-term exposure can lead to cancer.For the treatment of organic pollutants,electrocatalytic oxidation treatment and catalytic hydrogenation reduction treatment based on nanocatalyst are effective methods to remove organic pollutants.The traditional preparation methods of nanocatalysts are mainly physical and chemical methods,which have the problems of high equipment requirements,heavy use of chemical reagents and environmental pollution.Biosynthesis technology of nanomaterials is considered as a new green preparation technology.Compared with traditional synthesis methods,it is non-toxic,clean and environmentally friendly,and can well solve the environmental problems caused by physical and chemical methods.At present,the process of biological preparation of nano-catalysts involves the synthesis of nano-materials through the use of microorganisms such as fungi and bacteria in nature,and extracts from plants and algae.In this paper,Bio-Pd/C and Bio-Pd-Ag/rGO nanocomposite catalysts were prepared by in-situ reduction of bacteria S.oneidensis MR-1.The nanocatalysts were characterized and applied to the electrocatalytic oxidation degradation of methyl orange and catalytic hydrogenation reduction of p-nitrophenol,respectively.The main research contents and results are as follows:(1)Bio-Pd/C nanocomposite catalyst was prepared by biological method.The morphology and composition of the catalyst were characterized by transmission electron microscope,scanning electron microscope and X-ray photoelectron spectroscopy.Bio-Pd/C gas diffusion electrode was prepared from the catalyst.The effects of current,pH and aeration conditions on the degradation of methyl orange wastewater were investigated.It was found that Pd in the prepared catalyst was amorphous and highly dispersed in the connected pores of biochar,with regular shape and particle size of 10-15 nm.The removal effect of Bio-Pd/C gas diffusion system on methyl orange was better than that of biochar gas diffusion system.After 30 minutes of reaction,the removal rate of methyl orange in Bio-Pd/C gas diffusion system reached 99%and that of TOC reached 53%.The experimental results show that the degradation rate of methyl orange can be improved by increasing current,decreasing pH and increasing aeration.(2)Bio-Pd-Ag/rGO nanocomposite catalyst was prepared by biological method.The morphology and composition of the catalyst were characterized by transmission electron microscope,X-ray diffraction spectrum,X-ray photoelectron spectrum,Fourier transform infrared spectrum and Raman spectrum.It was applied to the study of catalytic hydrogenation and reduction of p-nitrophenol,and the molding state and catalytic effect of the catalyst under the conditions of different bacterial concentration and different metal proportion were investigated.When bacteria concentration OD600=1.0,Pd:Ag=1:1 in preparation of Bio-Pd-Ag/rGO morphology of nanometer composite catalyst which has the best conditions and the optimal catalytic hydrogenation effect,the response time to 20 min,the nitro phenol degradation rate of 99%,the apparent rate constant was 0.2413 min-1,comparing with other methods preparation of catalyst,biosynthesis of Bio-Pd-Ag/rGO nanocomposite catalyst has excellent removal effect of p-nitrophenol.Organic wastewater entering the natural water environment will not only cause pollution to the water body,but also indirectly endanger human life and health.In this experiment,nano-composite catalysts prepared by biological method can efficiently remove refractory organic pollutants through electrocatalytic oxidation and catalytic hydrogenation reduction reactions,so as to protect the earth's ecological environment.