Gas liquid mass-transfer behaviors in aqueous alcohol solutions were studied in an internal-loop airlift reactor of 5-m height and 0.28-m i.d. in the superficial gas velocity (U-g) range from 2.0 to 10.0 cm/s. Air and aqueous n-butanol solutions were used as the gas and liquid phases, respectively. It was found that the volumetric mass-transfer coefficient decreased with increasing n-butanol concentration (C-A) below a critical C-A value of 0.5 wt % and increased with increasing C-A above this concentration. To confirm this result, further experiments were also carried out in a bubble column of 0.12-m i.d. at U-g = 6 cm/s, and similar results were obtained. Further analysis showed that the value of k(la)/alpha(g) was independent of the superficial gas velocity and equal to 0.211/s in the air water system; however, it decreased with increasing CA up to 0.25 wt % in n-butanol solutions, and further addition of n-butanol had no effect on k(1a)/alpha(g). A critical C-A value of 0.5 wt % was also found for the liquid-side mass-transfer coefficient (k(1)). Below this concentration, k(1) decreased with increasing C-A, whereas above this concentration, further addition of n-butanol had no effect k(1).