Ch-1菌还原碱性介质中Cr(Ⅵ)的反应动力学

Kinetic of Cr(Ⅵ) reduction in alkaline media by Ch-1 bacteria

通过研究Ch-1菌还原碱性介质中Cr(Ⅵ)过程Cr(Ⅵ)浓度的变化规律,确定初始pH值和细菌接种量对反应速率的影响,建立不同条件下的反应动力学方程,计算相应的反应表观活化能,得到了按细菌接种量划分的Ch-1菌还原Cr(Ⅵ)的反应控制区域图。研究结果表明:当初始pH值为8～10时,Ch-1菌还原Cr(Ⅵ)的反应速率基本相同,当pH<8和pH>10时,反应速率逐渐减小。Ch-1菌还原Cr(Ⅵ)的反应为零级反应,但细菌接种量减少,反应速率减小,反应表观活化能增大。细菌接种量分别为50%,30%,20%,10%和5%时对应的反应速率常数分别为57.521 1,51.630 6,45.976 4,24.002 5和7.326 5,表观活化能分别为6.89,14.75,19.24,33.54和72.52 kJ/mol;Cr(Ⅵ)的细菌还原反应随着细菌接种量的增加逐渐由内扩散控制区转入混合控制区,当细菌接种量减少至近9%时,转入化学反应控制区,并由此确定了Ch-1菌还原Cr(Ⅵ)的最佳工艺条件:温度为30℃,pH值10,细菌接种量为20%。

The effects of initial pH value and Ch-1 bacteria inoculation amounts on reaction rate were confirmed with the change of Cr（Ⅵ） concentration in the process of bio-reduction. Kinetic equation in each condition was established and the corresponding apparent activation energy was also calculated. Meanwhile, controlling range of Cr（Ⅵ） reduction by Ch-1 bacteria with changing the bacteria inoculation amounts was obtained. The results show that the reaction rates are approximately the same at pH value of 8 to 10 and decrease gradually when pH〈8 and pH〉 10. The reaction order of Cr（Ⅵ） reduction in alkaline media by bacteria is zero. The reaction rate decreases and the apparent activation energy increases with the decrease of bacteria inoculation amounts. The reaction rate constants in bacteria inoculation of 50%, 30%, 20%, 10%, 5% are respectively listed as follows： 57.521 1, 51.630 6, 45.976 4, 24.002 5 and 7.326 5, and the apparent activation energys are 6.89, 14.75, 19.24, 33.54 and 72.52 kJ/mol, respectively. The rate determining step for reduction of Cr（Ⅵ） by bacteria is varied from inner diffusion, mixed control to chemical reaction with the inoculation amounts being changed from 50% to 9%. And the optimized technological conditions are as follows： temperature of 30 ℃, pH=10 and 20% bacteria inoculation amounts.