Abstract: The study on the thermodynamics and kinetics of Cd²⁺ adsorption in phaeozem and burozem showed that within the test range,Cd²⁺ adsorption was increased with its increasing initial concentration,and phaeozem had a much higher Cd²⁺ adsorption capacity than burozem.When the Cd²⁺ concentration in adsorption equilibrium was 20 mg·kg^-1,the amount of adsorbed Cd²⁺ was 1 485.2 mg·kg^-1 in phaeozem,but 700.6 mg·kg^-1 in burozem.The adsorption isotherm of Cd²⁺ in the two soils could significantly conform to Langmuir,Freundlich and Henry equations,while Temkin equation was not applicable to describe the isothermal adsorption process of Cd²⁺ in phaeozem and burozem.The maximum adsorption of Cd²⁺ in phaeozem and burozem was 5 939.3 and 2 790 mg·kg^-1,respectively,according to Langmuir formulation.The Cd²⁺ adsorption in test soils was a rapid reaction,with 90% of Cd²⁺ adsorption in the first 2 min and reached equilibrium in 15～30 min.First-order dynamic equation was the optimal model to describe the kinetics of Cd²⁺ adsorption,while the other models in point were Elovich and Two-constant equations.The adsorption rate of Cd²⁺ in test soils was increased with its increasing initial concentration,but decreased with its increasing adsorbed amount.Under low concentrations of Cd²⁺,the decrease of its adsorption rate with time was more quickly in phaeozem than in burozem.

Key words: Cadmium, Phaeozem, Burozem, Adsorption reaction, Thermodynamics, Chemical kinetics