| With the rapid development of our economy and industry,the problem of heavy metal pollution is becoming more and more serious.As one of heavy metal pollution source,zinc was widely existed in wastewater of electroplating industry and metallurgical industry.Excessive zinc in water can destroy the water ecological balance and can cause threat the existence of aquatic organism,even human health.Compared with physical and chemistry ways,biological method is more friendly and economical than in wastewater zinc removal.Moreover,it would not cause secondary pollution,thus it has received wide attention at home and abroad.Compared with growing cells and dead cells,resting cells may have greater potential because it don't need any nutrients but also a variety of physiological and metabolic avtivity.In recent years,nano materials have been widely used in aviation,military,medical and other fields,because of its unique surface effect,small size effect,quantum size effect and so on.Therefore,the synthesis of nanomaterials with unique properties is becoming a research hotspot at home and abroad.Compared with the traditional synthesis method,biological synthesis has a lot of advantages such as clean,mild reaction conditions,economical,simple operation and so on,at the same time,biosynthesis of nano material has good dispersity,stability and biocompatibility and accommodative which caused the extensive concern from all over the world.So,can we find an organism that both have the ablity of zinc bioremvoal and biosynthesis nano-materials?This paper studied a strain Pseudoalteromonas sp.DSBS(DSBS)which has been proved to have good heavy metals removal ability,it not only has good capability of removing heavy metals,but also can synthesis metal nanometer materials at the same time.The mechanism of zinc removal and nanoparticles synthesis was mainly investigated.The results combined heavy metal treatment and resource recycling which was of significant meaning to environment.he main research contents and results are as follows:The resting cells had a maximal zinc removal of 54 mg/L when the initial concentration was 64 mg/L;DSBS had excellent zinc removal ability in pH 3-7,salinity below 1%and temperature 25?.And DSBS is an aerobic strain that its zinc removal process need oxygen.Sodium lactate was the suitable carbon source of DSBS in zinc removal process.The basic mechanism of zinc removal by DSBS resting cells was obtained through the investigation of zinc removal ability of each part of DSBS:firstly,part of zinc was adsorbed by extracellular polymeric substance(EPS)and functional groups on cell wall.And some zinc also would go through the cell wall and was accumulated in periplasmic space.However,there was a limit of periplasmic space in zinc accumulation that the zinc that could not be existed in it would be transported intracellularly and be induced to precipitate by enzyme.The images of SEM and TEM showed that there were a lot of granular precipitation with diameter 30 nm adhered on the bacterial surface.The results depicted that DSBS could secrete polysaccharide to control the growth of crystal nucleus in addition to provide adhesion sites for precipitation.The results of EDS and XRD showed that the precipitate was an organic zinc sulfide compound substance mainly composed of zinc sulfide,calcium phosphate and other organic substances.This indicated that it is feasible to synthesize zinc sulfide nanomaterials with DSBS.The results of zeta potential experiment showed that the zinc sulfide nanomaterials are type of sphalerite.This study proved that bacterial periplasmic space had the ability of accumulating zinc and it was a new bacterial zinc removal mechanism.The results provided a new insight to bacterial heavy metal removal.Besides,the resting cells controlled zinc sulfide nanoparticles using the removed zinc which accomplished the combination of heavy metal govern and resource recycling.The results provided a new way to environmental protection and resource recycling and reuse. |
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