Environmental Science

Fouling Deliberately

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Science  22 Jul 2005:
Vol. 309, Issue 5734, pp. 537
DOI: 10.1126/science.309.5734.537a

An ongoing problem in water purification is the fouling of membranes by particulates (such as clay, silt, or algae) and by natural organic matter (NOM), which comes from the biological degradation of plants and humus. NOM typically consists of molecules in the range of 1 to 2 kD, but can form aggregates of much larger size. It has not been clear which components of NOM are responsible for fouling, although it is known that more hydrophobic membranes are more susceptible.

Clark et al.turn this problem on its head by using a hydrophobic polymer as the basis for a new adsorbent material that can be used to pretreat water. Polysulfone, a common membrane material, was dissolved in an organic solvent mixture and then injected into water, which is not a solvent for the polymer. The polysulfone formed particles with a diameter around 50 nm, which then rapidly clustered into micrometer-sized colloidal aggregates with large surface area. When added to local drinking water, the aggregates adsorbed only a small fraction of the NOM from the water, but these molecules were the ones responsible for most of the fouling of a 20-kD filtration membrane. — MSL

Langmuir 10.1021/la050186l (2005).

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