Effect of Humidity on Adsorption Behavior of Acetaldehyde on a Diatomaceous Material

The effect of humidity on the adsorption behavior of acetaldehyde was examined on a diatomaceous material (DM) both in a flow and a closed systems. All the adsorption isotherms of acetaldehyde with the flow system at 298, 313 and 323 K obeyed the Langmuir equation for 10% relative humidity (RH) in all the regions of partial pressure of acetaldehyde (PCH3CHO). In 60% RH, the adsorption isotherms obeyed the Langmuir equation up to 0.07 atm of PCH3CHO. Heat of adsorption in 60% RH in the range of PCH3CHO was larger than that in 10% RH, indicating strong interaction of adsorbed acetaldehyde and water. At PCH3CHO higher than 0.07 atm in 60% RH, the adsorption isotherms deviated from the Langmuir equation and the adsorbed amounts linearly increased with increasing PCH3CHO. The linearity suggested that acetaldehyde dissolved into multilayer of water on the surface of DM predominantly, in the range of PCH3CHO. Adsorption behavior obtained in a closed system suggested that both the initial adsorption rate and the adsorption rate constrant in 60% RH were twice those in 10% RH.