The present study reports the effect of contact time, nature of electrolyte, and temperature on the sorption kinetics of Cd2+ by manganese dioxide, which is the most active oxide in soils and sediments. The sorption kinetics of Cd2+ by manganese dioxide is evaluated at pH 6 in different electrolytes in the temperatures range 293-323 K. The solid samples are equilibrated in 0.45 mmol.L-1 Cd2+ and different electrolytes at pH 6. The results indicate that sorption of Cd2+ increases with time and temperature and the system attains equilibrium within 60 min in KNO3 as the electrolyte. However, in the presence of 0.001 M KH2PO(4) sorption of Cd2+ increases and the time for equilibrium shifts to 90 min. The data second-order kinetics model and the calculated rate constant k and initial sorption rate h increases with increasing temperature phosphate treatment. Among the calculated thermodynamic activation parameters the positive values of Delta H-double dagger and Delta G(double dagger) show the sorption process to be endothermic and nonspontaneous, while the Delta S-double dagger being negative indicates a decrease in randomness of the system during sorption process at the solid-liquid interface. The free energy of activation decreases from 15.95 kJ.mol(-1) in nitrate to 8.76 kJ.mol(-1) in phosphate. These observations suggest that the rate controlling step in Cd2+ sorption is diffusionally controlled, a fact that has been proved by application of Fick's law.