The kinetics of adsorption in a spherical pellet for nonlinear equilibrium adsorption systems was examined. There was considered the case when the mass transfer resistance appears in a solid and fluid phase. Kinetic equation applicable for entire range of Biot number and the exponent in Freundlich equation was proposed. This equation is correct for a short time of saturation. On the base of kinetic curves investigated experimentally the values of the apparent diffusion coefficient in the pellet and external mass transfer coefficients were estimated.