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Charged Polysulfone Membrane

Normal (uncharged) polysulfone (PS) membranes contain physical pores that can pass salts; they are used in ultrafiltration water treatment. Charged PS membranes have been chemically sulfonated to create the ability to reject dissolved salts. The sulfonation process permanently affixes sulfonate (SO3-) groups on the membrane surface, in a process similar to that used to give cation exchange resins their charge characteristics. These negatively charged sites repel anions, and indirectly repel the cations also due to the cations' attraction to anions in the concentrate solution. Charged PS membranes have salt rejection and chlorine tolerance characteristics similar to cellulosic membranes, and offer a permeate flux rate comparable to thin-film composite membranes. However, charged PS membranes are more easily fouled by any divalent or trivalent cations, such as calcium, magnesium, or iron existing in the feedwater. See Also: Polyamide Polysulfone Electrodialysis Reverse Osmosis Polysulfone Reverse Osmosis Thin-Film Composite Membrane