An analysis of mass transport fluxes in titania-based mesoporous ceramic matrices

Titania particles, with a particle size of 40. ±. 5 microns, having pore sizes of 300. °A, 1000. °A and 2000. °A were modified with Ethylenediamine-N,N'-tetra (methyl phosphonic) acid (EDTPA), to yield mesoporous ceramic cationic-exchange supports for potential use in bioseparations. Our objective is to understand the influence of the pore size on solute transport, and the solute binding phenomena in mesoporous titania based supports. Pulse injection techniques were used to elucidate and estimate the individual solute transfer parameters in matrices with different pore sizes. Elution peaks were approximated to a Gaussian distribution and the corresponding height-equivalent-of a theoretical-plate (HETP) was calculated. Elution profiles obtained under retained and unretained conditions were used to estimate the corresponding HETP contribution. Using equations in the literature, the theoretical numbers of transfer units (dimensionless groups) were estimated in order to identify the dominant transport mechanism for the adsorption processes.In the case of mesoporous ceramic materials, pore diffusion was established to be the rate limiting process for the adsorption of the solute. When the pore size nearly equaled the solute size, the diffusion phenomena seemed to be hindered; as pore size increased, there seemed to be an enhanced mode of solute transport in these matrices.