Abstract: The effect of BSA on the adsorption equilibrium of Cd(Ⅱ)onto δ-MnO₂ is studied. The results show that in the presence of BSA, the adsorption-pH curve of Cd(Ⅱ) onto δ-MnO₂ is of S-shape. BSA enables the Cd(Ⅱ) adsorption to leap toward higher pH direction and its adsorption amount decreases with the increase of ionic strength. In the presence of BSA at a pH lower than 3.0, the Cd(Ⅱ) adsorption isotherm follows Langmuir equation but the Cd(Ⅱ) saturated adsorption amount is reduced from 34.97 mg/g to 22.83 mg/g. When pH = 5.0, the Cd(Ⅱ) adsorption is little influenced by BSA. When pH = 2.0 and pH=3.0 and BSA concentration is lower than 20 mg/L, the Cd(Ⅱ) adsorption is evidently reduced with the increase of BSA concentration. When BSA concentration is greater than 20 mg/L, the Cd(Ⅱ) adsorption is hardly reduced. The study helps increase the understanding of Cd(Ⅱ)'s environmental chemical behavior.

Key words: BSA, Cd(Ⅱ), δ-MnO₂, Adsorption, Ionic strength