沼泽红假单胞菌（Rhodopseudomonas palustris）转化去除铅镉污染的研究

【作者】 贠妮；

【导师】 袁凤英； 白红娟；

【作者基本信息】 中北大学 ， 安全技术及工程， 2007， 硕士

【摘要】 镉、铅因广泛应用于电子、电镀等领域，业已成为污水中重金属离子的重要污染源而备受人们的关注。传统的处理重金属废水的技术包括：化学沉淀法、离子交换法以及液模法等，这些传统技术存在着易二次污染、去除效率低、成本高等缺点，尤其是当废水中重金属离子浓度在1～100mg／L时。因此，寻找有效的重金属废水去除技术对于建立“无害空间”的生态安全目标有着极为重要的意义。本文在系统综述生物去除机制研究进展以及光合细菌在废水处理中应用的基础之上，以铅镉重金属废水为研究对象，研究沼泽红假单胞菌对其去除的整个动力学过程。主要内容包括：（1）理化条件对N菌株的生长及去除pb²⁺、Cd²⁺的影响实验的优化：（2）去除pb²⁺、Cd²⁺的动力学的模拟；（3）固定化沼泽红假单胞菌去除pb²⁺、Cd²⁺的动态实验的工艺参数的优化；（4）沼泽红假单胞菌去除重金属离子的机理进的初步探讨。研究结果表明：（1）沼泽红假单胞菌N菌株对铅离子的最佳去除和生长条件为：pH=7.0，温度30℃，厌氧光照培养，接种量0.6g·L^-1。沼泽红假单胞菌N菌株对镉离子的最佳去除和生长条件分别为：pH=7.0，温度30℃，好氧黑暗，接种量0.6g·L^-1。（2）pb²⁺初始浓度为50、100、150、200mg·L^-1时，沼泽红假单胞菌N菌株对pb²⁺的去除符合一级动力学特征，半衰期分别为2.7h、3.0h、4.1h、10.1h，去除动力学方程分别为：lnC=-0.1531t+3.7842、lnC=-0.1535t+4.2319、lnC=-0.1040t+4.7598、lnC=-0.0827t+5.0316。Cd²⁺初始浓度为10、20、25、30mg·L^-1时，沼泽红假单胞菌N菌株对Cd²⁺的去除符合一级动力学特征，半衰期分别为42h、50h、53h、55h，去除动力学方程分别为：C=10.920e^-0.0162t、C=24.599e^-0.018t、C=30.036e^-0.0192t、C=37.532e^-0.0192t。（3）研究了连续流动态固定化沼泽红假单胞菌去除铅、镉模拟废水，结果显示，处理含铅废水的最佳工艺条件为：pH=7.0，温度30℃，水力停留时间12h，固定化细胞投加量20g。处理含镉废水的最佳工艺条件：pH=7.0，温度30℃，水力停留时间12h，固定化细胞投加量30g，鼓氧量DO值为2.0～3.0mg·L^-1。固定化沼泽红假单胞菌对浓度小于50mg·L^-1Pb²⁺去除能力较强，去除率大于95％。对于浓度小于25mg·L^-1时的镉离子去除率大于90％。（4）通过X-射线衍射谱图分析证实沼泽红假单胞菌对Pb²⁺、Cd²⁺转化产物的硫化铅、硫化镉沉淀；通过不同浓度铅、镉对沼泽红假单胞菌产生半胱氨酸脱巯基酶活力的影响分析，及不同浓度Pb²⁺、Cd²⁺对半胱氨酸脱巯基酶同工酶谱的分析，得出在低浓度Pb²⁺、Cd²⁺作用下，生物体自身在外源物侵扰时存在着保护机制，N菌株内的半胱氨酸脱巯基酶出现了活性增强，随着Pb²⁺、Cd²⁺作用浓度的进一步增加，其的毒性作用加剧，从而使酶的结构和功能受到相应的破坏，活性下降。Pb、Cd在菌体细胞不同部位的分布结果表明，N菌株对Pb²⁺的去除大部分在原生质中、对Cd²⁺的去除主要在细胞壁上。细胞的透射电子显微镜观察含铅、镉培养液中生长的菌体细胞分别存在大量的高电子密集颗粒物，空白对照中生长的菌体细胞未见这些颗粒物，推测高电子密集层为铅、镉沉积物。沼泽红假单胞菌同化型硫酸还原途径及脱巯基酶的作用分析，在低浓度铅、镉离子存在时沼泽红假单胞菌以同化型硫酸还原，把硫酸盐转变成还原态的硫合成半胱氨酸，在金属离子存在时，该菌体出于解毒的目的，通过半胱氨酸脱巯酶的作用，生成S^2-，并进一步与Pb²⁺、Cd²⁺反应产生金属硫化铅沉淀，然后排出体外。更多还原

【Abstract】 The element Cadmium, Lead are paid more and more attention because of their heavy metal ions which come from some associated fields such as the electronics and electroplate fields, have become an important source of pollution in waste water. Conventional methods for removing metals from aqueous solutions include chemical precipitation, ion exchange, membrane technologies etc. these processes may be ineffective or extremely expensive especially when the metals in solution are in the range of 1-100mg/L. Another major disadvantage with conventional treatment technologies is the production of toxic chemical sludge and is not eco-friendly. Therefore, removal of toxic heavy metals to an environmentally safe level in a cost effective and environment friendly manner assumes great importance.Based on systemic summarizing research progress of biology removal mechanism and application of photosynthetic bacteria to wastewater disposal, taking heavy metal wastewater of lead and cadmium as the investigation object, this paper researched on the entire dynamics process of Rhodopseudomonas palustris to its removal. The main content includes:（1） Optimize infection experiment of which the physical and chemical condition to growth of N strain and removal of Pb²⁺and Cd²⁺.（2） Dynamics simulation on the removal of Pb²⁺and Cd²⁺.（3） Optimize craftwork parameters of dynamical experiment which using Immobilized Rhodopseudomonas palustris to remove Pb²⁺.（4） Preliminary discussion on the mechanism of removing heavy metal ion using Rhodopseudomonas palustrisInvestigation results illustrate that:（1） The best removal and growth condition of Pb²⁺ using Rhodopseudomonas palustris N strain is pH7, 30℃, anaerobic and illumination, inoculation amount 0．6 g/L. And the same time, the optimum removal and growth condition of Cd²⁺ using Rhodopseudomonas palustris N strain is pH7, aerobic culture in darkness, 30℃, quantity of inoculation 0．6 g/L. （2） When Pb²⁺ in concentrations of 75, 100, 150, 200mg/L, the removal of Pb²⁺ using Rhodopseudomonas palustris N strain followed the first order kinetics equation characteristic, the half life were 2．7h, 3．0h, 4．1 h, 10．1h and the dynamic equations were lnC=-0．1531t+3．784, lnC=-0．1535t+4．231, lnC=-0．1040t+4．7598, lnC=-0．0827t+5．0316 in turn.Condition of Cd²⁺ in concentrations of 10、20、25、30mg/L, the removal of Cd²⁺ using Rhodopseudomonas palustris N strain followed the first order kinetics equation characteristic, too. The half life were 42h、50h、53h、55h and the dynamic equations were C= 10．920e^-0．0162t、C=24．599e^-0．018t、C=30．036e^-0．0192t、C=37．532e^-0．0192t in turn.（3） Dynamical disposal of wastewater containing Pb²⁺ and Cd²⁺ using small-scale continuous flow is simulated. The test results show that the removal ability of Immobilized Rhodopseudomonas palustris is the best of all in condition that the concentration of Pb²⁺ is less than 50mg·L^-1 .The optimum conditions of Pb²⁺ wastewater treatment is pH7, 30℃, Hydraulic Retention Time of 12h, and Immobilized cell dose of 20g. The optimum conditions of Cd²⁺ wastewater treatment is pH7, 30℃, Hydraulic Retention Time of 12h, and Immobilized cell dose of 30g and medium quantity oxygen.X-ray diffraction analysis illustrates that the transform productions of Pb²⁺ and Cd²⁺ using Rhodopseudomonas palustris are precipitation of PbS, and CdS.The effects of Pb²⁺ and Cd²⁺in different concentrations on the specific activity of cysteine desulfhydrase and its isozymograms which produced by Rhodopseudomonas palustris N strain were analyzed. Results indicate that in environment of low concentration for Pb²⁺ and Cd²⁺, organism itself exists protecting mechanism when suffer from intrusion of xenobiotics and the activity of cysteine desulfhydrase in N strain boosts up. With the further increase Pb²⁺ and Cd²⁺’s concentration, its toxicity becomes more and more acuteness, and the corresponding afetermath is that configuration and function for enzyme is destroyed and its activity is reduced.Distributing result of Cd in different part for thalli indicates that removal Cd²⁺ of using N strain is mainly on cell wall. TEM illustrates that thalli cells which grow in Pb²⁺ and Cd²⁺ Tissue Culture Solution have large amount of high electron coarctation grain. However, thalli cells which grow in blank comparison do not have that grain. Thereout, that grain may be precipitation of Pb²⁺ and Cd²⁺.Analysis to approach of assimilative sulfate reduction for Rhodopseudomonas palustris and function of desulfhydrase show that Rhodopseudomonas palustris was reduced by assimilative sulfate in condition of low concentration for Pb²⁺ and Cd²⁺. In this reaction, sulphate transmits to cysteine desulfhydrase . when exists metal ion, in order to detoxification, that thrall produces through acts with cysteine desulfhydrase, and then reacts with Pb²⁺ and Cd²⁺ to form precipitation of metal sulfìde, and then that precipitation is discharged out of body.更多还原