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 met allic surface may be advantageous. Plastics are more inert and weaker ice crystal nucleating agents, and possess low ice-plastic adhesion. B atch experiments were performed to test the viability of a freeze puri fication technique. One-liter samples of an aqueous feed solution cont aining 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 utiliz ed 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 free ze purification technique are discussed. A brief comparison with alter nate freeze purification techniques is also mentioned.