Reduction Of V(?) By Shewanella Oneidensis MR-1 And Shewanella Putrefaciens And Its Mechanism

Vanadium is one of the major pollutants in most parts of the world.it is considered to be a relatively abundant element in soil,water body and atmosphere.it is also a major trace metal in chemical fuels.it is widely used in the production of non-ferrous metals such as titanium alloys in aerospace and nuclear industries.Because of the extensive use of vanadium by human beings,the problem of vanadium pollution in atmosphere,water and soil is also becoming more and more prominent.?anadium in the natural environment exists in a variety of oxidation states:????,V???and V???,among which vanadium pentoxide is the most common form of existence.the toxicity of vanadium increases with the increase of its valence state,which means that the redox behavior of vanadium can control the migration and geochemical cycle of vanadium in the environment.a small amount of pentavalent vanadium in the environment can be reduced to low-priced vanadium by redox reaction in the natural environment,and a large number of existing vanadium pollution can only be effectively treated by manual intervention.In recent years,research on vanadium morphology has become a hot topic,and the widely accepted method is microbial reduction.under laboratory conditions,a group of strains with V???tolerance and Fe???reduction function were cultured to explore the reduction mechanism of V???and to investigate the influencing factors of microbial removal.The main findings are as follows:The effects of shewanella oneidensis mr-1 and shewanella putrefaciens on V??? reduction and its influencing factors were studied in laboratory culture.The biotransformation of different concentrations of V???mediated by S.oneidensis MR-1 and S.putrefaciens is closely related to the tolerance characteristics of vanadium by microorganisms.Low concentration V???has little effect on the growth of vanadium,while bacterial growth is inhibited at high concentration,which in turn inhibits the reduction rate of V???;the optimum growth p H of the strain is neutral,and the weak alkaline environment is more favorable to the reduction of V???than the acidic environment.through SEM and XPS analysis,V???and V???were present on the surface of mycelium after 5 d of treatment,which confirmed that S.oneidensis MR-1 and S.putrefaciens were also accompanied by a small amount of adsorption while reducing the V???.Effect of exogenous addition of electron shuttle substances on S.oneidensis MR-1 and S.putrefaciens reduction V???under laboratory culture conditions.Exogenous addition of anthraquinone-2,6-sodium bisulfonate?AQDS?accelerated V???reduction.After exogenous addition of 1 mmol/L AQDS culture for 7 d,the reduction rate of V???increased to 69.1%by S.oneidensis MR-1,and the reduction rate of V???increased to41.3%by S.putrefaciens.The high concentration AQDS has a slight inhibitory effect.Exogenous addition of low concentration riboflavin has little effect on the reduction of V???.When exogenous addition of riboflavin concentration exceeds 4?mol/L,it will accelerate the reduction of V???by microorganisms.S.oneidensis MR-1 and S.putrefaciens on V???reduction and its influencing factors after adding Fe???,and the mechanism of the reduced strain was characterized by SEM and XPS methods.when V???is added to the anaerobic system of S.oneidensis MR-1 and Fe???,it is quickly reduced.S.oneidensis MR-1 can directly reduce the V???reaction,but the efficiency of direct reduction will be reduced and limited.when V???was added to the anaerobic system of S.putrefaciens and Fe???,the reduction rate was accelerated but lower than that of the S.oneidensis MR-1 group S.oneidensis MR-1 and S.putrefaciens can directly reduce the V???,but the efficiency of direct reduction will be reduced and limited.scanning electron microscopy?SEM?showed that the addition of V???had a certain toxic effect on two iron reducing bacteria.XPS results showed that V???and V???formed V?OH?₃ precipitates and Fe???and Fe???also existed in the system during the reduction.therefore,V???microbial reduction can provide a useful pathway for the detoxification of vanadium.The experiments simulated the leaching and reduction of vanadium by S.oneidensis MR-1 and S.putrefaciens in vanadium-bearing mineral environment.The effects of S.oneidensis MR-1 and S.putrefaciens on the leaching of vanadium in vanadium magnetite and vanadium-bearing coal and the reduction and detoxification of V???,different forms of iron and p H on S.oneidensis MR-1 leaching and reduction V???.The experiments showed that S.oneidensis MR-1 and S.putrefaciens bacteria suspension to vanadium-containing mineral solution accelerated the leaching of vanadium and the reduction of V???.the effect of different initial p H on the reduction of vanadium by leaching was compared.The results show that when the p H is neutral S.oneidensis MR-1the leaching reduction V???is the best,and the weak alkaline environment is more favorable than the acidic environment for the leaching of vanadium-containing minerals and the reduction of V???in the leaching solution.The leaching and reduction effect of S.oneidensis MR-1 on V???was the best in the exogenous addition of magnetite,hematite and ferric chloride test.After 14 d,the vanadium leaching concentration of vanadium magnetite and vanadium-bearing coal in vanadium-containing minerals increased to 24.3mg/kg?15.6 mg/kg,and the V???reduction rate of vanadium magnetite and vanadium-bearing stone coal in vanadium-containing minerals increased to 85.1%and54.2%,respectively.The fourier infrared?FTIR?spectra of vanadium-containing minerals before and after microbial leaching showed that,the basic constituent units of vanadium mica in vanadium-containing minerals were distorted and collapsed,and vanadium ions were dissolved.The XPS spectra before and after the microbial leaching of vanadium-containing minerals showed that could leach vanadium from vanadium magnetite and vanadium-containing coal and reduce V???in solution to V???,Fe???to Fe???.