Chemical Engineering Science, Vol. 42, No. I, pp. 97-103, 1987. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFED OOO’-2509/87 $3.00 + 0.00 Pnnted in Great Britain. Pergamon Journals Ltd. zyxwvu TEMPERATURE SENSITIVE GELS AS EXTRACTION SOLVENTS ROBERTO F. S. FREITAS Department of Chemical Engineering, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 3C000, Brazil and E. L. CUSSLER Department of Chemical Engineering, Materials Science, University of Minnesota, Minneapolis, MN 55455, U.S.A. (Received 2 January 1986) Abstract-Crosslinked poly(N-isopropylacrylamide) gel and crosslinked copolymers of 97 y0 NJ- diethylacrylamide and 3 y0 sodium methacrylate which are swollen with water collapse abruptly at 33°C and near 55”C, respectively. These collapses apparently occur zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJI because each gel is near its lower critical solution temperature. The gels can be used to extract water and low molecular weight solutes from macromolecular solutions. After they have extracted the water, the gels can be regenerated by warming to release the absorbed water. The resulting separation process is effective for proteins and other polymers, and may be operated with waste heat which is usually discarded. This paper reports the extraction of water from photograph in Fig. 1. The three tubes in this figure all solutions of macromolecules such as proteins using contain the same amount of gel. The gel in the left hand crosslinked polymer gels whose swelling in water is a tube is dry. The gel in the centre tube is swollen in water dramatic function of temperature. One example of at 30°C; the meniscus of the excess water is visible these gels, polyisopropylacrylamide, is shown in the nearer the top of the tube. The gel in the right hand Fig. 1. The swelling of poly(N-isopropylacrylamide). Each of the tubes shown contains the same amount of gel. That on the left is dry; that in the centre is swollen in water at 30°C; that on the right is swollen in water at 35°C. The altered swelling serves as the basis for the size selective extraction plxess in Fig. 2. 97