Kinetics Characterization of Ions Release Under Dynamic and Batch Conditions.Strong Acid and Strong Base Type Ion Exchange Resins

摘要

The purpose of this study has been to investigate the influence of key parameters (i.e.,the structure of the resin organic polymer and its particle size,as well as the temperature of the process) on the release of calcium and fluoride ions from cationic and anionic ion exchange resins of strong character,in order to develop a formulation for a controlled release of the mentioned ions,that are present in organomineral tissues.Kinetics parameters were evaluated under dynamic and batch conditions.It has been observed that the rate of Ca2+ and F~- release increases when temperature increases and particle size decreases.Because of the larger pore volumes that provide a greater effective surface area,macroporous ion exchangers observe a higher rate of ions release than those of gel nature.Results obtained in this study are well interpreted by the models based on intraparticle diffusion as rate controlling step of the ion exchange process.The effective rate of release,B (obtained from the application of mentioned models),of the respective ions in the resin phase describes quantitatively the kinetic process.Linear dependences of -log (B) with the resin particles diameters can be applied to the estimation of B values for very low particle size resins,materials commonly used in the development of controlled release formulations.