Study On The Biosorption Of Cr(â…¥) By Active S.cerevisiae And On The Exploration Of Its Mechanism

With the development of industry and the improvement of the people's living standard, water pollution comes to be an increasingly serious problem in our daily life, while the demanding of water quality also enhances. Biosorption is a newly arisen water treatment method. It has advantages of resourceful raw material, diverse species, low cost, simple biosorption equipment, easy-to-do operation, great disposal speed, large absorption quantity, selectiveness in absorption, and is especially good for the disposal of water with low-concentrated heavy mental. What's more, it is also valued for restoring noble metal. Thus it receives great attention from researchers at home and abroad and will definitely enjoy a promising prospect and a wide applied foreground.In the case of post-treatment, general chemical method is effective enough to analyze metal ions absorbed by the organism which can be applied once more in the absorption.The subject carefully studies the influence of pretreat, duration of absorption, temperature, cell age, interfering ions, nutrient substance and concentration of absorbent towards the absorption of Cr (VI) by active cerevisiae fermentum. Optimum condition for absorption is also examined in the study. Besides, the subject made a contrast test on the absorption behavior by the active cerevisiae fermentum and the inactive one. Further experiment was made to acclimatize active cerevisiae fermentum which was later used in absorption. The study proves high performance.Series of experiments worked out the following optimum for absorption : rotational speed of the shaker - 145r/min; pretreat-1 %HC1; length of time-one hour; pH = 2; temperature-the higher the better(normal atmospheric temperature also works); cell age-24 hours. Experiments shows little interfere from common ions in water; mere influence from the addition of nutrient substance; the higher the concentration, the bigger the amount of absorption, however, absorption stops when it comes to certain amount; high analytic ratio, that is to say, can be used for secondary absorption.As to the Acclimated S. cerevisiae, its absorptive capacity increases by 20.39% compared with that of the Non- acclimated S. cerevisiae. Fitting constant of Langmuir R~ = 0.7702 shows there is a stage of active in the absorption of Cr (VI) by active cerevisiae fermentum. The influence by pH on the absorption by the acclimatized cerevisiae fermentum tends toward a similar curve with those by the non-acclimatized cerevisiae fermentum. When pH=2 , the absorption ratio of Cr ( VI) by 50mg/L got to 96.87%; If pH ranges from 4 to 5, the amount of absorption may varies a lot; however, if pH>5 then the ratio decreased to 50% or so.Experiments of acetification and hydrolyzation farther prove the effect of differentfunctional groups on the cell wall in the process. When pH=2, the absorptive capacity after acetification would decline and the ratio of absorption also decreased by 12.5%. Hydrolyzation would release a small quantity of carboxyl, consequently the ratio rose by 8.13%. When pH=5, the ratio climbed by 43.08%. After hydroiyzation, it dropped by 15.29%. From the experiment, we deduce that when pH=5, it is functional groups except carboxyl that performs principally during the absorption of Cr( â…£ )by cerevisiae fermentum.