| This paper summarized the harmfulness and the present situation of water heavy metal pollution. The main technology for treatments of wastewater containing heavy metal at this stage was described. The types and sources of biosorbent, the factors of affecting on the heavy metal adsorption, the mechanism of adsorption, the biosorption mechanism and the application of biosorbent were aslo introduced.As the long-term environmental selection and adaptive evolution, microorganisms grown in the environment of heavy metal pollution are able to tolerate heavy metals. Therefore, It has become a hot research topic of environmental protection that to purify the heavy metal wastewater and to repair the heavy metal pollution by taking use of the remarkable property of microorganisms.One strain named Pseudomonas plecoglossicida C-18 with great efficiency of cadmium resistance was successfully screened in our study. The basic research was carried out systematically on the bacteria anti-cadmium mechanism and various physical and chemical factors affecting biosorption on Cd(Ⅱ).The main content of this study are as follows:1.A stain with strong ability to resistance cadmium was successfully isolated from 16 anti-mercury stains by the selected medium with Cd(Ⅱ).The strain could grow normally in the Cd (Ⅱ) concentration of 900mg/L of liquid medium and Cd(Ⅱ) concentration of 1600mg/L Cd(Ⅱ) of the plate respectively.Cell morphology and structure,physiology, biochemistry and molecular biology of the bacteria were classified. The strain C-18 was initially identified as Pseudomonas plecoglossicida and the phylogenetic tree was structured.2.By optimizing the medium composition, using the molasses and yeast extract as the main nutrition, under training of 24h, the value of OD600 stands for the biomass of strain C-18 reached to about 4.8.3.The strain C-18 served as biosorbent to study the impact of the physical and chemical factors on bacteria adsorbed Cd (Ⅱ) and verify the optimum adsorption conditions by optimizing orthogonal experiments.Nurturing by the condition of Concentration in the adsorbent 1.2g/L, Cd (Ⅱ) the initial concentration of 100mg/L, strain age 24h, pH7.0, temperature 30℃, speed 200r/min conditions, the adsorption 12h, the Cd (Ⅱ) adsorption rate and adsorption capacity achieved respectively 88.8%,and 74mg/g.4.By Adsorption of Cd (Ⅱ) in the C-18 cell with O.lmol/LHC1 desorption 30min, The desorption rate exceeded 80%.5.Pseudomonas C-18 with Cd (Ⅱ) adsorpted can be divided into fast adsorption and slow adsorption stage, in the first 30min of the adsorption process, the adsorption rate could reach 90%of the total absorption rate, and the adsorption achieved balance within 12h.Pseudomonas C-18 on the Cd (Ⅱ) Langmuir adsorption model and Freundlich isotherm consistent with adsorption model. The dynamic model of adsorption of Cd (Ⅱ) consistent with the pseudo-second order kinetic model.6. Bacterial cells of Pseudomonas C-18 with adsorpted Cd (Ⅱ) appeared rough surface with folds mixed up with sediment can be showed by SEM. Adsorption of Cd (Ⅱ) bacteria before and after FTIR analysis showed that, hydroxyl, amide, carboxyl on C-18 cell surface and other active groups involved in Cd (Ⅱ) in the complex reaction. Inductively coupled plasma emission spectrometry (ICP) analysed the concentration in the digestion solution and the supernatant cell after Pseudomonas C-18 adsorbed Cd (Ⅱ), which was found the total concentration is equal to the solution concentration of Cd (Ⅱ). The results of Comparing dead cells and viable adsorbent adsorbent Cd (Ⅱ) adsorption effects shows that both the adsorption rate is equivalent. Which indicates the adsorption of Cd (Ⅱ) by Pseudomonas C-18 belongs to passive adsorption, as a result of Cd (Ⅱ) deposited on the cell surface through the complexation of functional groups on the cell surface.
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