This new pseudo-homogeneous model describes the absorption rate in the presence of dispersed second liquid phase or solid catalyst particles. In contrast to previous models, it considers the diffusion process and chemical reaction inside the dispersed phase. The absorption rate is defined in the case of first- and zero-order reactions for both continuous and dispersed phases. The concentration of particles from the bulk phase to the gas-liquid boundary layer replaces the initial concentration to the balance equation for the liquid boundary layer at the gas-liquid interface. For mass transport in the bulk phase, steady-state film theory, while in the gas-liquid boundary layer, unsteady-state film-penetration theory is applied. The effect of mass-transfer and reaction kinetic parameters, as well as the particle size on the absorption rate, is described as well as the simulated data verified by previous experimental studies.