| The new technology of remoⅥng Cr(Ⅵ) from wastewater by microbe has become a new hotspot recently. In this article, firstly, we separate some bacteria from enⅥronmental which is contaminated by Cr(Ⅵ) or not. Secondly, we compare the efficiency of these bacteria and screen out a bacteria whose capacity of reducing Cr(Ⅵ) is best. Though the identifying, we know the bacteria is belonging to E.cloacae. On this base, the optimum condition (including the initial concentration of Cr(Ⅵ), the time, the temperature and pH, the proportion of bacteria and wastewater) has been found, and the effect of heavy metal has also been discovered. In addition, the works focus on the reducing kinetics has been done finally. The result of this research show :1 The reducing efficiency of PX-2 is better than that which has been found before. In the condition of 30 C,pH=7 and the volume of bacteria reaching 55ml, 100mg/L Cr(Ⅵ) can be reduced in 72 hours. The reducing rate can reach more than 99%.2 Though a series of physiological and biochemical experiment, we discover that the PX-2 is belonging to E.cloacae.3 The four heavy metals including Cu2+,Zn2+Cr2+,Ni2+can inhibit the reducing of Cr(Ⅵ) obⅥously. The inhibition of the heavy metals from large to small is arranged asCd2+>Zn2+>Ni2>Cu2+.4 Through the study of bacterial enzymatic kinetics, we can conclude that the great mass of Cr(Ⅵ) is reduced by H2S exist in primary solution, and the subsequent reducing of bacteria account for only 35.70%. The Monod equation fits the kinetic process well. And the parameter we get accord with the fact. But we haven't taken the H2S which exists in the in primary solution into account, so the kinetic equation can not be apply in produce process and should be mended.The study of us can be the base of subsequent separate , selection and identify of Cr(Ⅵ) reducing bacteria. And it also help to study the mechanism of reducing Cr(Ⅵ) by bacteria. |
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