The Biosorption Rule Of Low Concentration Lead (Ⅱ) And Admium (Ⅱ) To The Dominant Bacteria In Natural Water

There are many heavy metals coming from human being activities in natural water.With the development of industral productions, the contents of heavy metals are increasing, and the natural waters polluted are becoming greater and greater, which wastes precious metals, damages enviroments and hazards human health. The migration and transformation of heavy metals in nater water are affected significantly by the solid phases in the water, and reactions occurring at surface play a dominant role in detering metal partioning between the solid and solution phase, and thus, the potential impact of metals in the aqueous enviroments. Due to the high surface reactivity and large surface areas, microorganism in natural water is the important solid phase and is able to adsorb and enrich all kinds of pollutants. The adsorption is affected by the physicochemical characteristics of aquatic environment, and reactivity , status and quantity of microorganism. There are many plankton bacteria in natural water, some of which are called dominant bacteria because of quantity. Dominant bacteria have influences on space distribution of heavy metals. The plankton bacteria of YITong river in Changchun city were studied to adsorb heavy metals in different aquatic environments, search adsorption thermodynamic equalization and kinetics process, and investigate the effects of accompany ions. The results are following: The equilibrium time of the adsorption of cadmium(Ⅱ)and lead (Ⅱ) ions onto dominant live bacteria, dead bacteria and polysaccharide are individually 12h, 3h and 8h. The kinetic processes of the adsorption included fast phase and slow phase ,and the latter followed the second-order rate expression. pH has different influences on the biosoption of Pb2+ and Cd2+ ions onto dominant live bacteria, dead bacteria and polysaccharide, and the biosorption processes include two stages. But different biosorptions are of different cut-off points. The live bacteria exhibit the highest Pb2+ uptake capacity at the initial pH value of 7, and show the highest Cd2+ uptake capacity at the initial pH value of 5. The dead bacteria exhibited the highest Pb2+ uptake capacity at the initial pH value of 4.5, and show the highest Cd2+ uptake capacity at the initial pH value of 6. The polysaccharide of cell wall exhibits the highest Pb2+ uptake capacity at the initial pH value of 4.5, and shows the highest Cd2+ uptake capacity at the initial pH value of 5.0. The live bacteria show the highest Pb2+ uptake capacity at 30℃, while the live bacteria show the highest Cd2+ uptake capacity at 25℃. The dead bacteria show the highest Pb2+, Cd2+ uptake capacity at 30℃. The temperature has no influences on the biosoption of Pb2+ and Cd2+ ions onto the polysaccharide cell wall. The equilibrium was well described by Langmuir and Freundlich isotherm models in the studied concentration range of cadmium(Ⅱ)and lead (Ⅱ) ions.