A mathematical model for oxidation of aqueous alkaline solution of sodium dithionite using air as an oxidizing medium in a foam-bed reactor has been developed under pseudo-zero-order conditions of reaction and was found to be in good agreement with the experiments. Reactor conditions were 30°C at atmospheric pressure and surfactant used in the foam contactor was octyl phenoxy polyethoxyethanol (Triton X-100). The results of simulation for concentration profiles of the dissolved gas-phase reactant inside foam film based on above model are presented for different gas flow rates, reaction rates, and times of contact. The effects of variables such as superficial gas velocity and initial liquid-phase reactant concentration on conversion are also studied and compared with experiments on oxidation of sodium dithionite. The results indicate that the conversion increases with the increase in the superficial air velocity and initial dithionite concentration. The model predicts the experimentally obtained conversions reasonably well.