| With the rapid development of the industry on mining, smelting, electroplating, electronics and fuel production, more and more lead, zinc and other heavy metals enter the soil or water environment through a variety of ways, which causes a serious threat to the ecological environment and human health. Using microbial treatment technology to remove heavy metals has become a new hot spot recently.In this experiment, we isolated and screened a strain which could highly resist on lead and zinc from the pioneer plant rhizosphere soil of Hunan lead-zinc mine. The main influence factors on the removal of Pb(Ⅱ) and Zn(Ⅱ) were investigated, and the related adsorption mechanism was also discussed, in order to provide reference for the industrial application of microbial remediation on heavy metal pollution in the future. The main research contents and results of this paper are as follows:(1) In the experiment,11 strains were isolated and purified from lead-zinc mining area, among the 3 preliminary screening patient strains, the highest tolerance strains HA as the experimental strains, which had high tolerance on Pb(Ⅱ) and Zn(Ⅱ), the removal efficiency of HA on Pb(Ⅱ) was higher than that of Zn(Ⅱ).The morphological characteristics of strain HA were studied, and the DNA were sequenced and analyzed, HA finally identified as Aspergillus oryzae.(2)The environmental conditions of resistant strains HA adsorption on Pb(Ⅱ) and Zn(Ⅱ) were optimized through the single factor experiment and orthogonal experiment, the conclusions are as follows:①In the experimental range of initial concentration of Pb(Ⅱ) and Zn(Ⅱ) (100-800 mg/L), the removal of Pb(Ⅱ) and Zn(Ⅱ) decreased with the increase of the initial concentration of Pb(II) and Zn(Ⅱ).The maximum biosorption was found at initial Pb(Ⅱ) and Zn(Ⅱ) of 100 mg/L and pH 5.0. Under such conditions, the adsorption rates of Pb(Ⅱ) and Zn(Ⅱ) was 97.8% and 54.1%, respectively, the growth curve analysis showed that, The growth of HA turned into stable period after 25 h, and the removal of Pb(Ⅱ) and Zn(Ⅱ) was relatively stable. When the inoculation quantity of HA was 1 mL, the Pb(Ⅱ) and Zn(Ⅱ) adsorption rate of increment was the fastest.②In based on the results of single factor experiment, the three significant level of the four impact factors (the initial concentrations of heavy metal ions, the pH, the inoculation quantity and adsorption time)on the removal of Pb(Ⅱand Zn(Ⅱ) of strain HA was selected to carrying out the orthogonal experiment.And ultimately, the optimal scheme on the removal of Pb(Ⅱ) and Zn(Ⅱ) of strain HA was determined:the initial concentration of Pb(Ⅱ) and Zn(Ⅱ) was 100mg/L, pH of medium was 5.5, the inoculation quantity of HA was 1.5 mL(0.01 g/mL), the adsorption time is 3 d.(3) The absorption mechanism of HA on Pb(Ⅱ) and Zn(Ⅱ) was discussed through the isothermal adsorption model, dynamic analysis, SEM, EDS and IR techniques, and the adsorption sites on the HA cell adsorption of Pb(Ⅱ) and Zn(Ⅱ) was also studied, the conclusions are as follows:①It was found that the adsorption process of Pb(Ⅱ) and Zn(Ⅱ) by HA was in accordance with Langmuir adsorption model to analyze the strain HA adsorption of Pb(Ⅱ) and Zn(Ⅱ), and its adsorption was given priority with monolayer adsorption. During the dynamic adsorption process of Pb(Ⅱ) and Zn(Ⅱ) by HA, a pseudo-second-order adsorption kinetics model was more suitable for describing the adsorption performance of HA, and the effect of HA on adsorption of Pb(Ⅱ) was significantly higher than on Zn(Ⅱ).②The results show that the adsorption and accumulation of strain HA against Pb(Ⅱ) and Zn(Ⅱ) was mainly in cell wall and intracellular accumulation to study the adsorption sites on the HA cell adsorption of Pb(Ⅱ) and Zn(Ⅱ), and the amount of cell wall adsorption was higher than the accumulation of intracellular, it explained that some components and active groups on the cell wall of strain HA had strong ability on combination of Pb(Ⅱ) and Zn(Ⅱ).③It was observed that the surface of strain HA cell had lots of deposits with lead and zinc, through the scanning electron-microscope and energy spectrum analysis, after on adsorption of Pb(Ⅱ) and Zn(Ⅱ) strains. IR analysis showed that the functional groups of HA such ashydroxyl, alkyl, amide, carbonyl and phosphate group were involved in the adsorption process of Pb(Ⅱ) and Zn(Ⅱ) by HA, so that the characteristic peak position and intensity appeared different degree of change. |
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