Rhodopseudomonas Palustris (rhodopseudomonas Palustris) Transformation And Removal Of Lead And Cadmium Pollution

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.