Study On Biosorption And Cytotoxicity Of Uranium Containing Wastewater

Uranium-containing wastewater is a kind of radioactive wastewater which has wide variety of sources and huge risk to human health.When human are exposed to a certain amount of radioactive elements,they will damage,such as liver damage,kidneydamage,cancer and so on.The gene mutation and chromosomal variation caused by radionuclide radiation can also affect the next generation and cause serious consequences.A bacteria strain LYB13 with high adsorption rate and good tolerance of UO22+was screened from the vicinity of the 713 uranium mine in Shangrao,Jiangxi.The identification of 16SrDNA shows that the strain in the taxonomic belongs to the Pseudomonas and named Pseudomonas sp.LYB13.Pseudomonas sp.LYB13 was mutagenic by ultraviolet irradiation and NTG.Pseudomonas sp.UV27 with high adsorption rate and stable genetic property was obtained.The adsorption rate reached 96.3%,which was increased by 9.39%compared with the rate of adsorption of the original strain.In order to obtain the maximum amount of bacteria,the ingredients and fermentation conditions of the fermentation medium were taken preliminarily optimization in this study.Then,plackett-Burman experimental design and response surface analysis based on Box-Behnken were applied to optimize the fermentation conditions.The optimum conditions:temperature was 31.5?.the concentration of peptone was 12.5g/L,the concentration of NaCl was 3.87g/L,pH was 6.0,rotational speed was 160r/min,the concentration was beef paste 3.6g/L and liquid volume was 80ml.The maximum absorbance of the fermentation broth was 0.5587,which increased by 42.16%compared with the absorption value of 0.393 before the optimization.After obtaining the maximum amount of bacteria,the mutant strain was applied to the adsorption of uranium ion-containing wastewater.The adsorption efficiencies of this bacterium to uranium ions under the conditions of the different influencing factors were studied.The adsorption capacity reached 590.04mg/g,when the optimum conditions:time was 120min.UO22+ initial concentration was 100mg/L,temperature was 30?.bacterial age was 40h and pH was 6.The results of desorption experiments showed that Na2CO3 and NaHCO3 exhibited excellent desorption capacity,and the desorption rate were above 89%.To optimize the biosorption process,the optimal kinetic model and the thermodynamics parameters of the adsorption of uranium by the strain were investigated.Second-order kinetic model was described better than the first-order kinetics,and R2 value of second-order kinetics equation was about 0.936.The R2 of Langmuir equation was about 0.999 and it was optimal thermodynamic model.The biosorption reaction was endothermic and spontaneous.To test its biological safety after biosorption of uranium-containing wastewater,the cytotoxicity of residual wastewater was evaluated by MTT method.The relative survival rate of cells was greatly improved compared with that before adsorption.Due to the influence of UO22+,MCF-7 cells are blocked at S stage,which inhibits cell division and proliferation,and ultimately leads to apoptosis.