The Systematic Study of Porous Monoliths to Measure Diffusion Induced by Hydrochloric Acid

There is the open question of the effect of loaded and non-loaded hydrogels with CaCO3 on diffusion kinetics. Formulations of PEDGA solutions were created containing varying concentrations of CaCO3 since higher concentrations would result in the material to develop yield stresses. The formulation was polymerized into flat monolothis using UV light rays. The 200 µm monoliths were swelled in H2O for 24 hours. Then, were subjected to a diffusive dissolution experiment and submerged into different concentrations of HCl (1 M/L to 0.06 M/L) and CaCO3 (0% to 25%). Time measurements were taken assuming that the longer the hydrogel was soaked in HCl the less CaCO3 and the more porosity. Pictures taken with an SEM of the porous dissolution fronts measured over time show the diffusion reaction scheme fits a model of diffusion of the square root of time. Also, a pH sensitive dye experiment was carried out in the porous hydrogels. The methyl orange soaked hydrogels were put in an aqueous HCl bath, and the movement of the concentration front was measured assuming the dye is trapped and the reaction is limited by diffusion of the acidic front. Rearranging the diffusion equations, diffusion coefficients were retrieved for the reactions.