Study On Biosynthesis And Catalytic Performance Of Non-precious Metal Nanocomposites

Dye wastewater has high chroma,complex organic components,strong carcinogenicity,and is difficult to degrade.Direct discharge without treatment will cause adverse effects on the environment.Among the existing treatment methods such as adsorption,flocculation and precipitation,ultrafiltration membranes and catalytic degradation,the catalytic degradation method is the most widely used,but this relies on the development of new high-efficiency catalysts.In this paper,Shewanella oneidensis MR-1 was used to synthesize new nano-catalysts Cu/CNTs,Fe₂O₃/TNTs,Cu₇S₄/rGO nanocomposites and characterize their properties.On this basis,the catalytic degradation ability and mechanism of organic pollutants in the environment were studied.The main research contents and results are as follows:（1）Copper nanoparticles（Cu NPs）were supported on carbon nanotubes（CNTs）in situ by S.oneidensis MR-1 to form Cu/CNTs nanocomposites.Use transmission electron microscope（TEM）,X-ray photoelectron spectroscopy（XPS）,Raman spectroscopy（Raman）,high-resolution transmission electron microscope（HRTEM）,scanning electron microscope（SEM）,X-ray diffractometer（XRD）,etc.characterization;the catalytic reduction performance of Cu/CNTs nanocomposites on 4-Nitrophenol（4-NP）under different loading,dosage,pH and temperature conditions was investigated.The results show that Cu NPs with a diameter of about 4-10 nm have been successfully synthesized on the surface of CNTs and they have high crystallinity.Under the condition of 45°C and pH value of 10,the Cu/CNTs nanocatalyst with a loading ratio of 3 wt%can achieve 4-NP catalytic performance up to99.5%at 80 min,and the first-order kinetics constant k has been calculated to be 0.0532 min^-1.After 6 cycles of reaction,the Cu/CNTs nanocomposite still has higher catalytic degradation efficiency for 4-NP.（2）Fe₂O₃/TNTs nanocomposites were synthesized by S.oneidensis MR-1,and the decolorization of aniline blue by Fe₂O₃/TNTs nanocomposites with S.oneidensis MR-1 was investigated.High resolution transmission electron microscope（HRTEM）,scanning electron microscope（SEM）,energy dispersive spectrometer（EDS）,X-ray photoelectron spectroscopy（XPS）,UV-vis spectrophotometer（UV-vis）,X-ray diffraction（XRD）,etc.to characterize the structure and properties of Fe₂O₃/TNTs.The results showed that Fe₂O₃ was successfully supported on TiO₂ nanotubes（TNTs）.Under UV light irradiation,the decolorization rate of aniline blue by Fe₂O₃/TNTs can reach 97.5%in 60 minutes,showing good photocatalytic activity.The decolorization rate of aniline blue by S.oneidensis MR-1 and Fe₂O₃/TNTs nanocomposites was increased by 1.63%compared with S.oneidensis MR-1.（3）The Cu₇S₄/rGO was synthesized by biology and chemical respectively.Various characterization techniques indicate that nanocomposites synthesized by microorganisms have excellent catalytic activity.The photocatalytic efficiency of nanocomposite catalyst which synthesized by S.oneidensis MR-1 with Na₂S as sulfur source to methyl green（MG）was as high as 98.3%within 100 min,and five cycles of tests showed that it had high stability.The excellent performance of Cu₇S₄/rGO nanocomposite catalyst is due to the combination of Cu₇S₄ and rGO to enhance the active center and improve the electron transfer rate.The synthesis of nanocomposite materials by microbiological methods can effectively reduce the cost of traditional synthetic nanomaterials and reduce environmental pollution.Several nanocomposites synthesized in this study can efficiently degrade organic matter in water,which is beneficial to the protection of the ecological environment and human health,and explored its degradation mechanism,which has improved the reference for large-scale practical applications.