Study on the Adsorption Kinetics of Water Vapor on Collagen Fibers

The adsorption behaviors and adsorption kinetics of water on collagen fibers was investigated. It is shown that water uptaking on collagen fiber is rapid in the first 6 hours, followed by a slower rate until equilibrium is reached. The water adsorption on collagen fibers at equilibrium (water adsorption capacity, Me) increases with increasing the relative humidity of the environment. The more the relative humidity of the environment is, the longer the time is needed to reach equilibrium. Both the Lagergren first-order adsorption kinetics model and the second-order adsorption kinetics model were employed to analyze the experimental data, while the second-order adsorption kinetics model presented a better correlation to the experimental data, suggesting that there are chemical bonds in the adsorption. Intra-particle diffusion plots showed multi-linearity with three distinct stages: initial curved portion, followed by intermediate linear portion and then, a plateau. It was proposed that the water adsorption process in the intermediate linear part should be controlled by intra-particle diffusion. The linear plots, not passing through the origin, indicated that the intra-particle diffusion was not the only one factor controlling the water adsorption rate.