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Cadmium, lead, has become widely used in the field of electronics, electroplating and other important sources of heavy metal ions in the sewage much attention. Wastewater Treatment technologies include: chemical precipitation, ion exchange and liquid molding, these conventional techniques there is easy secondary pollution, low removal efficiency, cost disadvantages, especially when the concentration of heavy metal ions in the waste water in a ~ 100mg / L. Therefore, finding effective heavy metal wastewater removal technology has a very important significance for the establishment of \In this paper, a systematic review of biological removal Mechanisms of photosynthetic bacteria in wastewater treatment applications based on the heavy metals lead and cadmium waste water as the research object, to study R. palustris its removing the entire dynamic process. Optimization of the main contents include: (1) physical and chemical conditions of the N strain growth and to remove pb 2 , the Cd 2 of experiment: (2) removal the pb 2 the the Cd 2 dynamics simulation; (3) immobilized red swamp aeruginosa removal the pb 2 , the Cd 2 dynamic experimental optimization of process parameters; (4) R. palustris mechanism to remove heavy metal ions into the preliminary study. The results show that: (1) swamp rhodopseudomonas N strains of lead ions removal and growth conditions: pH = 7.0, temperature 30 ° C, anaerobic light culture, inoculation amount of 0.6g · L - 1 . R. palustris N strains of cadmium ion removal and growth conditions were: pH = 7.0, temperature 30 ° C, aerobic dark, the inoculation amount 0.6g L -1 . (2) pb 2 initial concentration of 50,100,150,200 mg · L -1 , R. palustris N strains pb 2 < the removal of / sup> the first dynamic characteristics, the half-life of 2.7h, 3.0h, 4.1h, 10.1h, remove the kinetic equation: lnC =-0.1531t 3.7842 lnC =-0.1535t 4.2319, LNC = -0.1040t 4.7598, lnC =-0.0827t 5.0316. Cd 2 initial concentration of of 10,20,25,30 mg · L -1 , N R. palustris strain on Cd 2 the removal of the first dynamic characteristics of the half-life of 42h, 50h, 53h, 55h, remove the kinetic equation: C = 10.920e -0.0162t C = 24.599e - 0.018t , C = 30.036e -0.0192t , C = 37.532e -0.0192t . (3) a continuous stream of dynamic immobilized R. palustris removal of lead, cadmium simulated wastewater, the results showed that the treatment of wastewater containing lead optimum conditions were: pH = 7.0, temperature 30 ° C, hydraulic retention time of 12h, immobilized cell dosage is 20g. Treatment of waste water containing cadmium optimum process conditions: pH = 7.0, temperature 30 ° C, hydraulic retention time of 12h, immobilized cell dosage 30g drum oxygen DO value of 2.0 ~ 3.0 mg · L -1 . Immobilized R. palustris concentration of less than 50 mg · L -1 the Pb 2 removal ability, the removal efficiency of greater than 95%. Cadmium ion concentration is less than 25 mg · L -1 removal efficiency greater than 90%. (4) by X-ray diffraction pattern analysis confirmed that R. palustris on Pb 2 , Cd 2 transformation products of lead sulfide, cadmium sulfide precipitation; concentrations of lead, cadmium red swamp Pseudomonas cysteine ??off the the sulfhydryl enzyme activity analysis, and different concentrations of Pb 2 , the Cd 2 on cysteinyl acid de-mercapto isozymes analysis, the low concentration of Pb 2 , the Cd 2 under organism itself outside source was intrusive protection mechanisms cysteine ??within the N strain off the the sulfhydryl enzyme activity-enhanced with the Pb 2 , Cd 2 further action concentrations increase, exacerbate its toxic effects, destruction, so that the structure and function of the enzyme is decreased activity. Pb, Cd in different parts of the bacterial cell distribution results show that the N strain Pb 2 remove most of the protoplasm, on Cd the 2 removal in the cell wall on . A transmission electron microscope observation of the cell lead, cadmium culture medium the growth of bacterial cells there are a large number of high electron dense particles, bacterial cells grown in the blank control no these particles, suggesting that the high electron dense layer of lead, cadmium deposition thereof. R. palustris assimilation sulfate reduction pathway and off sulfhydryl enzyme, low concentrations of lead, cadmium ions red swamp aeruginosa to the assimilation of sulfate reduction, sulfate into the reduced form of sulfur synthetic cysteine, in the presence of metal ions, the bacterial cells, for the purpose of detoxification off via the cysteine ??sulfhydryl enzyme generates S the 2 - , and further Pb 2 , Cd 2 reaction produce metallic lead sulfide precipitation, and then excreted.
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