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Studies on Characteristics of Lead and Cadmium Adsorption to Organic Components of Natural Surface Coatings

Author: ZhaoYuXia
Tutor: KangChunLi
School: Jilin University
Course: Environmental Science
Keywords: Biofilm Organic matter Lead Cadmium Adsorption Extracellular polymeric Microbial dead body cells Microorganisms living cells
CLC: X52
Type: Master's thesis
Year: 2004
Downloads: 228
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Abstract

Water environment, the migration of pollutants, transforming its ultimate destination is likely to be mutual adsorption of pollutants with biofilm, and strongly influenced by the role and then move the biofilm. Related research has confirmed that biofilm organic matter plays an important role in the migration and transformation of heavy metals in water. Organic biofilm microorganisms and their secretion of extracellular polymeric substances. Extracellular polymers in the presence of a large number of anionic groups (carboxyl, hydroxyl, sulfate), organism cell wall of some of the surface having a network, and the coordinating ability of the group exists, such as a carboxyl group, a hydroxyl group, etc., and these groups by ionic or covalent bond formation with the adsorbed metal ions to achieve the purpose of adsorption of metal ions. At the same time, the metal may be deposited by settling or crystal chemical action on the cell surface, certain insoluble metal may also be the extracellular secretion or cell wall of a cavity capture deposition. Natural water directly cultured purified dominant bacteria in natural water bodies to train the biofilm more constraints, and strong seasonal, so this is the dominant strain of the dominant bacteria in the biofilm and natural water compared kinds of alternative to the dominant bacteria in the biofilm experiments. The experimental coating separation separation of natural waters, bacteria, medium plate after inoculation moved into the incubator and cultured at 28 ~ 30 ℃ 2 ~ 3 d, colonies were observed until the surface of the medium. Picked colonies to be purified with a vaccination needle aseptic line drawing, step by step in making good on the solid medium shifted within the incubator 28 ~ 30 ℃ culture, about 1 ~ 2 d, the growth of the colonies is strains purified advantage. Natural Biofilm slides as a substrate to culture. Will be processed through the 6:1 (v / v) H2O: soaking of HNO3 solution for 24 h, slides (50mm × 75 mm × 1 mm) LT; WP = 69 GT; placed polypropylene rack fixed to the rack placed in the the lake underwater at 30cm, cultured for 3 weeks. The polypropylene frame underwater maintain level state basically the same, so all slides ambient conditions. Can confirm by visual advantage colonies and the advantage of the water in the biofilm colonies are the same kinds of colonies, Gram staining and staining experiments on purified colonies were further identified the dominant strain of the water body substitutability. Culture, colonies expand the advantages of water picked the dominant strain of a small amount of water in the liquid medium, into the shaking culture at 28 ~ 30 ℃ Shaking Incubator, wait until the solution is relatively turbid, daily afternoon sampling measuring the optical density (570 nm UV spectrophotometer), remove the optical density is larger. After culturing the culture solution will be expanded into a dialysis bag, sealed and placed in deionized water in a beaker filled with, by means of magnetic stirring, and the culture solution was dialyzed to remove one of the sugars. 1 h intervals for a water, until it can not be detected glucose date. Dialysis after the suspension of the main bacterial cells and their extracellular polymeric substances, centrifuged at 17000 r · min-1 for 20 min, the supernatant using 0.45μm cellulose acetate membrane filter 2 or 3 times, to take After filtration, the the extracellular polymer solution was lyophilized in the lyophilizer weighing in 1000ml flask set the volume to a final concentration of 63 mg / L, is the desired solution of the extracellular polymer. After centrifugation, the centrifuge tube and the bottom of the substance as the desired bacterial live cells. Taken part of lyophilized is the microorganism required for the experiment of dead cells. In order to investigate biofilms each unit of the adsorption characteristics of lead, cadmium, and need to optimize adsorption conditions (adsorption time, initial pH, temperature). The results show that: adsorption time, each unit of lead, cadmium adsorption gradually increased extracellular polymeric substances, microorganisms dead cells and living cells at 6 h, 2 h and 1 h to reach adsorption balance; at pH 6, each unit sub adsorption amount of lead, cadmium, to achieve the maximum change of the adsorption amount of lead, cadmium and pH greater than 6 lt; WP = 70 gt; not obvious; temperature on each unit adsorption of lead, cadmium, therefore, take into account the ease of operation of the experiment, 25 ℃ selected experimental conditions. 20 mL of extracellular polymeric substances, sealed in a dialysis bag placed in a 200 mL contains seven different lead concentrations (1-7 mg · L-1) and the adsorption of the cadmium concentration (0.2-2 mg · L-1) fluid 6 h, the adsorption the extracellular polymeric adsorption thermodynamics of lead, cadmium experiment; containing seven different lead concentrations (1-7 mg · L-1) in 5 mL of cadmium concentration (0.2-2 mg · L- 1) of the adsorption solution in the test tube, were added to the living cells and dead cells, oscillation adsorption for 1 h or 2 h adsorption experiments. Adsorption at 25 ± 1 ℃ adsorption initial pH value was adjusted to 6.0 ± 0.1 with HNO3 or NaOH. Adsorption equilibrium, with FAAS or GFAAS determination of lead, cadmium concentration in the equilibrium solution, the experimental data obtained were used to Freundlich and Langmuir equation fitting analysis. The results showed that the Freundlich and Langmuir equation can be a very good description of the biofilm each Turbine the adsorption thermodynamic processes of lead, cadmium, each unit points to lead the largest adsorption capacity is greater than the maximum adsorption capacity of cadmium and KPb gt ; KCd, visible, each component adsorption capacity of lead were higher than cadmium, saturated adsorption easy reach of the lead. When the presence of coexisting ions, cadmium, each unit adsorption of lead were significantly inhibited, lead cadmium adsorption of each component. Studies have shown that the dynamics of the biofilm extracellular polymeric substances and bacterial cells under different pH and temperature on the adsorption process of lead, cadmium belong to a kinetic reaction. For lead, three adsorption capacity of the adsorbent for extracellular polymeric gt; live bacterial cells gt; bacterial dead cells, but not very different; For cadmium is bacterial living cells gt; bacterial dead cells gt; extracellular polymer.

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