Computer-aided modeling of controlled release through surface erosion with and without microencapsulation

Predictive models for diffusion-controlled particle dissolution are important for designing advanced and efficient solid products for controlled release applications. A computer-aided modeling framework was developed to derive the effective dissolution rates of multiple particles as the solid surface material eroded gradually into the surrounding liquid phase. The mathematical models were solved with numerical methods using the computational software MATLAB. Results from the models were imported into COMSOL Script to create three-dimensional plots of the particle size data as a function of time. The release model found for the monodispersed particles was manipulated to incorporate polydisperse solids, as these are found more frequently in chemical processes. The program was further developed to calculate the particle size as a function of time for particles encapsulated for use in controlled release. The parameters, such as radius size, coating material and encapsulation thickness, can be altered in the computer models to aid in the design of particles for different desired applications. Simulations produced conversion profiles and three-dimensional visualizations for the dissolution processes. Experiments for the dissolution of citric acid in water were performed using a reaction microcalorimeter to verify results found from the computer models