Separation Science and Technology, Vol.31, No.14, 1971-1977, 1996
Freeze Purification of Water Utilizing a Cold Plastic Surface and Ice-Liquid Separation with a Centrifuge
Freeze purification utilizing a cold plastic surface rather than a metallic surface may be advantageous. Plastics are more inert and weaker ice crystal nucleating agents, and possess low ice-plastic adhesion. Batch experiments were performed to test the viability of a freeze purification technique. One-liter samples of an aqueous feed solution containing 20 g/L sodium chloride were contacted with a 350-cm(2) area of polyethylene terephthalate surface at 256 K for 10 minutes. About 200 mt of ice-liquid mass was obtained. A centrifugal technique was utilized to separate solid ice crystals from adhering liquid. An average of 60 mt of solid ice containing 1.9 g/L salt was recovered. Ice crystal grain characteristics and conditions to improve efficiency of the freeze purification technique are discussed. A brief comparison with alternate freeze purification techniques is also mentioned.