Effect of Particle Size on the Adsorption and Desorption Properties of Oxide Nanoparticles

Using water molecules as a model adsorbing compound, the effect of particle size on the adsorption and desorption properties of porous oxide nanoparticles (NPs) was investigated at different temperatures. The moisture concentration on the surface of NPs was measured by monitoring the infrared spectra peaks corresponding to the stretching vibration of water molecules. A transient multilayer model was developed to represent the fundamental steps in the process. The thermal stability of adsorbed species and the strength of bonding to the surface were evaluated by determining the activation energies of various steps. The results indicate that the surface interaction parameters are both temperature and particle-size-dependent. Smaller NPs have a higher saturated surface concentration and a slower response to purging and desorption. As temperature decreases, NPs exhibit a higher saturated moisture concentration and are more prone to the adsorption of moisture and similar contaminants. (C) 2012 American Institute of Chemical Engineers AIChE J, 59: 1502-1510, 2013