Studies On Biosorption Of Uranium By Chlorella Pyrenoidosa

In the wasted water, uranium is a harmful contaminant to the environment, butthe traditional processes have many disadvantages, such as, trivial operation, high cost,secondary contamination, and so on. In recent years, microorganism,aglae and plantshave received more attention for their application potential in the field of remedy.Using biosorption to recover heavy metal has well foreground in resource utilization.Chlorella pyrenoidosa was used as the biosorbent to adsorb uranium. At first, thegrowth curve of C. pyrenoidosa and its tolerance to uranium were determined. Thefactors which influence the adsorption of uranium by C. pyrenoidosa wereinvestigated, including pH, N/P,temperature and the initial concentration of uranium.Moreover, the thermodynamics and kinetics of the adsorption were discussed, and itsmechanism was also investigated.In addition, the toxic effect of uranium on C.pyrenoidosaand and telorance were disscussed respctively.The results showed that two days later the growth of C. pyrenoidosa enteredlogarithmic phase, and ten days later for decline phase;when uranium concentration isabove 5.0mg/L, uranium ions obviously restrained the growth of C. pyrenoidosa, butC. pyrenoidosa represented high tolerance below this concentration,and that the pHand U(Ⅵ) concentration influence was significant and that the increases of pH as wellas U( ) concentration was beneficial to the U( ) absorption,however,theⅥⅥU(Ⅵ)absorption was affected less by the N/P and the temperature.The optimum conditionsto attenuate U(Ⅵ) were 20℃,pH6,U(Ⅵ) concentration at 3.4mg/L,and N/P 3/1, whichwere confirmed through orthogonal experiment. The results indicated that the reactionrate could be better described with pseudo 2nd-order model, and the adsorptioncapacities calculated by the model were consistent with the actual measurements. Atwo-stage kinetic behavior was observed in the adsorption of U(VI), which showedvery rapid adsorption in the first few minutes and subsequent slowly uptake for longperiod and the correlation coefficients were more than 0.97. The adsorption pattern ofuranium by C. pyrenoidosa was in accordance with both Langmuir and Freundlichisotherms, and the former was fairly better.The toxic effect experiment show that the concentration for 50% reduction was 2.58 mg/L and Ch-square of dose response was precise. with increase of uraniumconcentration,the O2- and CAT were increased at the uranium concentration from 0.1mg/L to 1.0 mg/L.