Carbonation of barium sulfide to barium carbonate has been experimentally investigated in a foam-bed reactor. The variables studied are height of foam bed, initial concentration of barium sulfide in aqueous solution, gas flow rate, concentration of carbon dioxide in mixture with nitrogen, and surfactant concentration in the aqueous solution. The results indicate that the conversion in the reactor increases with increase in the foam height and initial concentration of barium sulfide. Interestingly, the effect of surfactant concentration on conversion reveals the importance of reverse diffusional flux of desorbing hydrogen sulfide gas. A simplified single-stage model based on the concept of resistances-in-series has been proposed to explain the experimental data in terms of an overall mass transfer coefficient or resistance. An unsteady-state model proposed for the start-up period, together with the simplified single-stage model for later times, provides an adequate approximate description of the complete operation of the foam-bed reactor.