Chemistry

Tolerating Chlorine

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Science  08 Aug 2008:
Vol. 321, Issue 5890, pp. 746
DOI: 10.1126/science.321.5890.746a

Supplies of fresh water are steadily dwindling, but salt water remains plentiful, and desalination is increasingly being used for purification. Membrane-based desalination methods require less energy than do distillation-based approaches and are now the dominant technology. However, a complex pretreatment protocol is necessary. Feed waters must be treated with chlorine to eliminate microorganisms that would deposit biofilms onto the membranes, but the chlorine must subsequently be removed to prevent chemical damage to the membranes. After passing through the membranes, the water is then rechlorinated before it is distributed for use. These dechlorination and rechlorination steps increase water purification costs. Park et al. have now developed membranes that can tolerate chlorine over a wide pH range. The membranes consist of disulfonated copolymers, which retain the desirable properties of polysulfone—a tough and stable thermoplastic—but are less hydrophobic. The membranes have the potential to be tailored for particular uses and should not require dechlorination of feeds. Further work is required to optimize water transport rates through, and salt retention by, these membranes. — JFU

Angew. Chem. Int. Ed. 47, 6019 (2008).

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