| Wastewater containing lead mainly comes from industrial production processes including the battery, metallurgy, metals, machinery, coating, electroplating and other industries. Due to heavy metals can not be biodegraded, they have been listed as one of priority control pollutants in water by various countries. At present, the physical and chemical methods have some limitations treating wastewater containing lead. Depending on the sorption and accumulation of heavy metals, biosorption method can be used to remedy the pollution effectively. Meanwhile, biosorption as an ideal method can treat waste water with simple operation, high selectivity and great treatment effect, so biosorption has been obtaining increasing scientific attention.The thesis screened out Rhodotorula sp. WT6-5 which could absorb and highly resist on lead from heavy metal tailings reservoir soil. The experiment studied its physiological and biochemical characteristics and detected its 16SrDNA sequence showing that WT6-5 was identified as Rhodortorula mucilaginosa. The thesis mainly studied WT6-5’s resistance and accumulation on lead. The thesis also studied biosorption conditions by single factor experiment and RSM. Meanwhile, the main biological adsorption mechanism was clarified using the kinetic equation, SEM and IR. Main conclusions are as follows:The thesis mainly studied on WT6-5’s resistance of Pb2+.The results showed that WT6-5 could highly resist on lead. Compared with ordinary culture medium strain tolerance was higher in YPD medium and the maximum tolerance doses were 750.00 mg/L. Lead was also biologically accumulated in the bacteria cells meanwhile.The thesis studied on WT6-5’s accumulation of Pb2+ and resist mechanism. The results showed that WT6-5’s accumulation rate of Pb2+ was up to the maximum after training 48h, the biggest accumulation rates for 5.00mg/L Pb2+ were 53.14%, for 10.00mg/L Pb2+ were 32.73%. WT6-5 resistant mechanism of Pb2+ included regulating the cell membrane permeability, regulating protein content of cells, accumulated a certain amount of Pb2+ and increased the activity of SOD enzyme.The thesis did a research on the removal of lead (II) ions from aqueous solution under the different conditions such as biosorption time, pH, initial concentrations of Pb2+, adsorbent dosage, temperature and shaker rotational speed. The results illustrated that the biosorption process was very fast. Within 10 minutes of contact, the biosorption rates reached 92.48% and the biosoption equilibrium time was 30 minutes. The pH of the solution had great effects on the adsorption of Pb2+. A proper pH scope was 4.50-6.00 and the optimum pH value were 5.00. The temperature affected the biosorption in a small extent.On the basis of single factor experiment, the optimum adsorption conditions of WT6-5 was investigated and determined by RSM. When the optimal conditions were contact time 8 minutes, initial concentrations of Pb2+ 6.80mg/L, the pH value 5.79, and shaker rotational speed 133.84r/min, the optimized biosorption rates were 96.58%, very closed to the predicted value of 97.30%.The thesis mainly studied on WT6-5’s biological adsorption mechanism. The results showed that the Langmuir and Freundlich isotherm models fitted the adsorption data with r= 0.9982 and r=0.8789 respectively. Accordingly, it was concluded that the biosorption process was well accorded with the Langmuir model. The biosorption kinetic data for Pb2+ onto WT6-5 was fitted by pseudo-second-order equations. Through analysis by SEM, WT6-5 strains occurred deformation, empty and fission of cells appeared after adsorption of lead ions and metal deposits accumulated in strains surface. Analysis by IR spectroscopy, carboxyl, hydroxyl, acylamino, C-N and sulfur carbonyl are main biosoption spots.The results suggest that WT6-5 is a suitable adsorbent for removing lead ions which can be widely applied in the water treatment projects. |
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