| With the development of social economy, people’s life has been improved a lot and all kinds of enterprise and factory produced. In the meanwhile, it has caused serious environmental problems, which directly influenced people’s health and country’s economic development. In recent years, rapid population growth, economic development, arbitrary discharge of domestic sewage and industrial wastewater have caused heavy pollution for water source. China is a country lacking of freshwater source, so heavy water pollution has a tremendous impact on people’s drinking water. Therefore, it is urgent to find solution to purify wastewater and prohibit arbitrary discharge of wastewater. Through continuous research, purification of sewage study has achieved much progress. For now, many wastewater control methods have came into real use.Nanoscale zero-valent iron has been widely applied in water pollution control for it has the advantages of small particle size, low reduction potential, strong reduction property. In our study, our study employed nanoscale zero-valent iron to disinfect Escherichia coli and Staphylococcus aureus. we chose two kinds of typical water pollution bacteria Escherichia coli and Staphylococcus aureus as target pollutants to study toxic effect and mechanism of nanoscale zero-valent iron on these two bacteria. In this work, Fe@Fe2O3 core-shell nanowires were synthesized by the reduction of ferric chloride with sodium borohydride at normal pressure and temperature.it adopted solid plate count method to study the bactericidal effect of different amount of Fe@Fe2O3 on different bacteria in the study. Through the research about survival probability of bacteria during different period, we could verify the disinfection effect of Fe@Fe2O3. The results of reactive oxygen species trapping experiments showed that the main reactive oxygen species sterilizing bacteria were hydrogen peroxide. In addition, we added different concentration of hydrogen peroxide to further explore the concentration effect of reactive oxygen species to disinfection Staphylococcus aureus. In the meanwhile, Escherichia coii and Staphylococcus aureus treated by Fe@Fe2O3 were characterized by SEM to study the variation of morphotogy. In order to study the quality of DNA and integrality of DNA chain of Escherichia coli and Staphylococcus aureus treated by Fe@Fe2O3, extraction experiments of these bacteria treated by Fe@Fe2O3 were conducted. The results showed the survival rate of two kinds of bacteria reduced with the increase of Fe@Fe2O3 amount. It revealed that growth of Staphylococcus aureus depended on Fe@Fe2O3 amount and Fe@Fe2O3 had antiseptic selectivity.Iron-reducing bacteria and iron oxides existed widely in nature, and iron-reducing bacteria reacted on surface of iron oxides to form ferrous species which could react with oxygen to generate reactive oxygen species to remove pollutants in environment. Thus, it was of great significance on assembling iron-reducing bacteria/iron oxides system to study the forms of iron-reducing bacteria and iron oxides, activity and forms of ferrous species. In this work, two kinds of nano-Fe2O3 with different exposed facets were synthesized through hydrothermal synthesis, nano-Fe2O3 cube (HNCs) and nano-Fe2O3 plate (HNPs) respectively. Interactions of two kinds of nano-Fe2O3 with different exposed facets and iron-reducing bacteria HS01 were studied. The concentrations of total iron and ferrous, amount of bacteria and pH value change in the suspension at intervals were measured. Nano- Fe2O3 after reaction was characterized by SEM, TEM, XRD and XPS. The results showed that treated by iron-reducing bacteria, the crystallinity of nano-Fe2O3 decreased, the concentration of ferrous increased while ferric decreased surface-bond. SEM images of nano- Fe2O3 treated by iron-reducing bacteria for 30 days showed that crystal surface tended to be irregular with heavy agglomerates. This work revealed iron-reducing bacteria played important role in the process of reduction and transformation of iron oxides. |
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