| Microbial flocculant is a kind of polymer material produced by microorganisms and has good flocculating activity.Because of its specific structure and composition,it has the advantages of safety,innocuity,biodegradation and no secondary pollution,and is widely used in water treatment,municipal sewage treatment and all kinds of industrial wastewater treatment.In this study,the bacterial strains with high efficient flocculation capacity were isolated from the soils contaminated with lead and zinc,and the nutritional conditions and fermentation conditions of the fermentation medium were optimized.The flocculation properties,structure and flocculation mechanism of microbial flocculants were studied.Main research results are as follows:?1?Strains isolated from soil contaminated with lead and zinc ZW5,the flocculating rate of 80.05%,the clay after 16 srdna homology,identified it as a Chryseobacterium sp.and named Chryseobacterium sp.ZW5.?2?A single factor experiment was carried out on the factors affecting the flocculant produced by the Chryseobacterium sp.ZW5.The best carbon source was sucrose,the nitrogen source was beef paste,the initial pH value was 7,the inoculation amount was 3%,the fermentation temperature was 30?,and the fermentation time was 30h,and the flocculation rate was up to 87.00%under this condition.Response surface methodology?RSM?was used to optimize the initial pH value,fermentation temperature and fermentation time conditions by using BBD response surface method.The order of the three factors was culture temperature>culture time>pH.According to the established model,the optimum process conditions are as follows:the incubation time is 32.54h,pH=7.51,the culture temperature is 28.80,the flocculation rate of kaolin is 86.84%,and the flocculation rate is86.81%.?3?Using the control variable method,the best mixing condition of microbial flocculant ZW5 for lead and zincmine simulated wastewater is Vfast=200r·min-1,tfast=45s,Vslow=40r·min-1,tslow=6min.Compared with the commonly used PAC flocculant in the treatment of simulated wastewater from lead-zincmine,the results show that the treatment effect of Chryseobacterium sp.ZW5 is better than that of PAC.?4?Chryseobacterium sp.ZW5 microbial flocculant,through the determination of polysaccharide and protein,found that the content of polysaccharide was 61.23%and the content of protein was 28.24%.Through analysis of infrared spectrum analysis,it can be seen that it contains a large number of hydroxyl,carboxyl,amino group and other functional groups,and the result of XRD analysis shows that its structure is crystal and organic matter The flocculant is identified as an exo polysaccharide microbial flocculant.?5?Through the bonding bond examination,the determination of Zeta potential and the contrast of SEM in the flocculation process of Chryseobacterium sp.ZW5 microbial flocculant,the flocculation mechanism is determined mainly by adsorption bridge and charge neutralization. |
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