The apparent kinetics of H2S removal by a ZnO-MnO desulfurizer were studied by thermogravimetric analysis. The experimental results show that the reaction is first order with respect to H2S concentration. In the temperature range 200-400 degrees C, the rate was controlled, at lower temperatures, by the grain surface reaction rate and, at higher temperatures, by the rate of intrapellet diffusion, respectively. The apparent kinetic behavior could be modeled by the equivalent grain model. The activation energies of surface reaction and solid diffusion were determined to be 11.842 and 20.865 kJ/mol, respectively. An optimum reaction temperature was observed. Reasons for this and why the solid diffusion activation energy exceeded that of the surface reaction are proposed.