Particle-liquid mass transfer in a three-phase mechanically agitated contactor has been studied. The experiments covered a broad range of particle sizes, liquid viscosities, and gas velocities besides variations in system geometry. The impellers used were upflow pitched blade turbine (PTU), downflow pitched blade turbine (PTD), and disk turbine (DT). The results indicated a unique relationship of the particle-liquid mass-transfer coefficient with respect to the critical suspension speed under gassed conditions, Ng. This observation has resulted in a simplified correlation for the particle-liquid mass-transfer coefficient.