| The wastewater produced by lead-zinc sulfide beneficiation contains a large number of heavy metal ions and organic flotation reagents,which not only causes pollution to the water environment,but also poses a serious threat to the reuse of wastewater and the health of aquatic organisms and human beings.Microbial flocculant were widely used in wastewater treatment due to their green,efficient and biodegradable characteristics.However,the composition of beneficiation wastewater is complex,and the microbial flocculant has different treatment effects on different pollutants in the wastewater,the mechanism of using microbial flocculant to treat mineral processing wastewater is not clear enough.In this study,microbial flocculant was used to treat lead-zinc sulfide beneficiation wastewater,and the removal rates of the main pollutants Pb(Ⅱ),Zn(Ⅱ)and xanthate were explored,and the removal mechanism was revealed.In this paper,Bacillus amyloliquefaciens ZWG was used as a flocculant-producing strain to extract microbial flocculant(MBF-Y).The effects of medium carbon source,nitrogen source,p H value,inoculum amount and incubation time on the production of MBF-Y were studied respectively.The results show that the flocculant has the best flocculation conditions and the best flocculation efficiency when sucrose is the carbon source,sodium nitrate is the nitrogen source,p H=5,the inoculum amount is 5%,and the flocculant is cultured for 24 h.The removal of Pb(Ⅱ),Zn(Ⅱ)and xanthate in wastewater by MBF-Y was explored.The effects of MBF-Y dosage,p H value,initial pollutant concentration and stirring reaction time on the treatment of Pb(Ⅱ),Zn(Ⅱ)and xanthate wastewater by MBF-Y were investigated.The results showed that the highest removal rates of MBF-Y for Pb(Ⅱ),Zn(Ⅱ)and xanthate in single pollutant wastewater were 88.0%,91.2%and 44.5%,respectively;in the coexistence wastewater of Pb(Ⅱ)and xanthate,the removal rates of Pb(Ⅱ)and xanthate were 98.5%and93.2%,respectively;when Zn(Ⅱ)and xanthate coexisted,under the optimal conditions.The removal rates of Zn(Ⅱ)and xanthate by MBF-Y were 34.3%and 89.9%,respectively.In the coexistence of Pb(Ⅱ)and Zn(Ⅱ)wastewater,the removal rates were 88.1%and 87.9%,respectively.The effects of coexisting ions on each other were explored,and it was found that Pb(Ⅱ)and Zn(Ⅱ)would compete for adsorption on MBF-Y,but the competition between them was small.When the concentration of Pb(Ⅱ)and Zn(Ⅱ)was higher,the removal effect of the two ions was better.In order to explore the effect of MBF-Y on the removal of pollutants in actual lead-zinc beneficiation wastewater,the effects of different factors on Pb(Ⅱ),Zn(Ⅱ)and xanthate in actual wastewater treated by MBF-Y were studied.The results showed that in the actual wastewater with complex water quality,MBF-Y still has good removal rates of Pb(Ⅱ),Zn(Ⅱ)and xanthate in the wastewater,which was 94.5%,61.8%and 49.6%,respectively.The main components of MBF-Y and the mechanism of removing Pb(Ⅱ),Zn(Ⅱ)and xanthate were analyzed by stability,ultraviolet spectroscopy,infrared spectroscopy(FT-IR),Zeta potential,XPS and microscopy.The adsorption of Pb(Ⅱ)and Zn(Ⅱ)by MBF-Y was fitted by adsorption isotherm model and kinetic model,and the adsorption types were analyzed.The results showed that:MBF-Y was a polysaccharide type microbial flocculant,and had a good flocculation effect in the range of p H 4～9 and temperature 4～80℃;in the process of removing Pb(Ⅱ),Zn(Ⅱ)and xanthate,the-OH and-COO~-on MBF-Y will combine with heavy metal ions and undergo an electrical neutralization reaction,and Pb(Ⅱ)and Zn(Ⅱ)will react with xanthate to form xanthate precipitation and ionic compounds,and sweep the suspended xanthate in the solution during the adsorption bridging settlement between ions and MBF-Y.The adsorption isotherm model fitting of MBF-Y adsorption process of Pb(Ⅱ)and Zn(Ⅱ)showed that:MBF-Y was easy to adsorb Pb(Ⅱ)and Zn(Ⅱ)in solution.The xanthate could affect the adsorption of Pb(Ⅱ)and Zn(Ⅱ)on MBF-Y,but the effect was small.The kinetic fitting results showed that the adsorption of MBF-Y to Pb(Ⅱ)not only had chemical adsorption but also a physical effect,and the adsorption of Zn(Ⅱ)was mainly chemical adsorption.Therefore,the removal of Pb(Ⅱ),Zn(Ⅱ)and xanthate in solution by MBF-Y was a multi-action process.This study can provide a certain experimental basis for the application of microbial flocculants in actual beneficiation wastewater,It has certain guiding significance for the study of new technology for mineral processing wastewater treatment. |
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