If a system uses the phenomenon of Marangoni convection, there will be more interfacial turbulence and this may dominate the mass transfer performance between the gas and liquid phases. Marangoni convection was applied in a gas-liquid contact device (dehumidifier) in this study to measure the effect of interfacial turbulence on the water vapor removal efficiency caused by adding a low surface tension component (99.5% ethanol) into the gas or liquid phase at room temperature. The differences in water vapor removal efficiency under different conditions with and without the addition of ethanol into the moist air or working solution (38-42 wt % aqueous lithium chloride solution) were observed. Since the Marangoni effect was more pronounced when the concentration of working solution was greater than a specific value, the trend line for water vapor removal efficiency in different solution concentrations was presented as a broken line in this study. The break in the trend line is the critical concentration of the working solution, and the value is about 40 wt % of aqueous lithium chloride solution. The experimental results show that addition of low surface tension ethanol into the gas phase was better than adding it into the liquid phase for the interfacial mass transfer performance in this gas-liquid contact device.