Novel resin-based ultrapurification system for reprocessing IPA in the semiconductor industry

There is an urgent need for the development of energy-efficient recycling and ultrapurification processes for 2-propanol solvent wastes generated from the semiconductor industry. In this paper, experimental results are presented that set the stage for the development of efficient resin-based closed-loop recycling systems for 2-propanol drying applications in the semiconductor industry. The process employs ion exchange resins to reduce cations and anions to low and sub-part-per-billion levels. Batch adsorption experiments were carried out in 2-propanol to determine the adsorption isotherms of various ions on commercially available ion exchange resins. The results indicate that ion exchange resins indeed have both high affinity and capacity for ions in the relatively nonpolar 2-propanol solvent. Under dynamic flow conditions, columns of appropriate column diameter and length packed with the resins were indeed capable of reducing ionic impurities to low parts-per-billion levels. In fact, long-term experiments indicate that these systems can generate ultrapure 2-propanol from relatively large volumes of solvent waste. In addition to the ionic impurities, it is necessary to remove water and organic contaminants from the solvent. Columns packed with activated carbon and molecular sieves were shown to be efficacious in removing organic and water impurities, respectively, from 2-propanol to low levels required for semiconductor applications.