Abstract: The process of removing dilute CO₂ from air by using the mixtures of K₂CO₃ and piperazine (PZ) was conducted in a random packed tower at 25 ℃.The results showed that PZ increased the absorption rate of CO₂ into aqueous K₂CO₃ much more effectively than MEA or DEA. The volumetric overall mass transfer coefficient (K_Ga) of dilute CO₂ absorption into K₂CO₃/PZ was measured.The K_Ga value was evaluated over the ranges of main operating variables: the concentration of CO₂ in inlet gas, gas flow rate, liquid loading, CO₂ loading in liquid phase,and the concentrations of K₂CO₃ and PZ. The test showed that K_Ga could be remarkably improved by increasing liquid loading and the concentration of PZ, and decreasing the concentration of CO₂ in inlet gas, as well as the gas flow rate and CO₂ loading in liquid phase.