Diffusion coefficient in gels

An effective medium approach, which uses hydraulic permeabilities to define the resistance of the fiber network to diffusion, has been used to estimate reduced diffusion coefficients in gels [77]. For a particle diffusing within a fiber matrix, the rate of particle diffusion is influenced by steric effects (due to the volume excluded by the fibers in the gel, which is inaccessible to the diffusing particle) and hydrodynamic effects (due to increased hydrodynamic drag on the diffusing particle caused by the presence of fibers). Recently, it was proposed that these two effects are multiplicative [78], so that the diffusion coefficient observed for particles in a fiber mesh can be predicted from ... 

The diffusion transport of H+ ions in polymer/silicate gels could be described by a modified version of Pick s first law and this formula provides an appropriate method for the prediction of the effective diffusion coefficient in gels if the structural parameters of the gels and the absolute diffusion coefficient are known. 

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