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Adsorption behavior and mechanism of an exopolysaccharide (EPS) secreted by a psychrotolerant bacterium Pseudoalteromonas sp.Bsi20310 isolated from Antarctic sea-ice,for lead(Ⅱ) from artificial freshwater and salty water were studied in this paper.Effects of salinity,pH and EPS dosage on Bsi20310 EPS adsorption characteristics for lead(Ⅱ) were evaluated by batch adsorption tests.The results indicated that Bsi20310 EPS presented better adsorption performance for lead(Ⅱ) in salty water than in freshwater.The equilibrium adsorption isotherms fitted well to both Langmuir and Freundlich isotherm models.Theoretical maximum adsorption capacity of 191.90 mg/g calculated according to Langmuir equation indicated that the EPS had a high adsorption capacity for lead(Ⅱ).The kinetics of lead(Ⅱ) adsorption onto Bsi20310 EPS could be better described by pseudo-second-order model than pseudo-first-order both in freshwater and in salty water.The external surface adsorption was the major adsorption mechanism while intraparticle diffusion was not the unitary rate-limiting step for the whole adsorption.The Fourier transform infrared spectroscopy (FT-IR) analysis indicated that the functional groups such as -OH,C=O and C-O-C on Bsi20310 EPS may play important roles as adsorption sites in lead(Ⅱ) biosorption.