Kinetics and Mechanism of Ion Exchange Process and Resin Deactivation during Ultra-Purification of Water

by Castro Rodriguez, Mary Elizabeth.

The semiconductor industry currently requires large volumes of ultra pure water (UPW), a point of concern due to the potential effects on the environment. Although reduction of water consumption by the industry is challenging, it can be accomplished by implementation of different strategies such as the reuse and recycling of water, the development of more efficient wet cleans and wet processes, and the conversion to dry process. The lack of a systematic approach to determine the optimum combination of water recycling and reusing and the optimum type of process configuration for recycle treatment need to be addressed in order to achieve more efficient water conservation. Specifically, multi-component interactions in ion exchange processes and the effect of these interactions on the separation efficiency have been neglected when dealing with water reusing and recycling. Ion exchange resins initially containing different concentrations of impurities were utilized in experiments to determine the effect that organic and ionic contaminants initially contained in the ion exchange resin have on the adsorption of ionic compounds. Experiments were performed with the tested ion exchange resins to determine the effect of organic compounds in the liquid phase. A combination of experimental and modeling methods were utilized to determine the fundamental equilibrium and kinetic parameters for ion-ion and/or ion-organic interactions. The concentrations under investigation are relevant to the ion exchange application in industrial ultra-pure water plants with. Experiments showed that adsorption of ionic compounds were affected by the amount of organic and ionic contaminants initially contained in the ion exchange resin. Additionally, experiments showed that the adsorption of organic compounds affects the capacity of the ion exchange resin, thus changing the efficiency of the system. The effect of organic impurities is not only due to the degradation of the exchange media, but also due to specific chemical interactions. These chemical interactions may enhance the adsorption kinetics; however, even in the case of kinetic enhancement, the key inhibition effect appears to be due to ionic transport effects, which cause pore and/or site blockage. By incorporating an organic removal process, such as granular activated carbon (GAC) or UV-oxidation to the recycle purification sequence, greater efficiency of the overall separation system can be achieved, resulting in reduced water usage and waste generation. 17