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AWWA MTC61144
- Chloramine Tolerance of Polyamide Membranes: Experiences with Iron-Coagulant Residuals
- Conference Proceeding by American Water Works Association, 03/01/2005
- Publisher: AWWA
$12.00$24.00
Reverse osmosis testing using monochloramine (NH<sub>2</sub>Cl) and free chlorine (HOCl) inthe presence of ferrous iron [Fe(II)] resulted in accelerated chlorination of polyamidemembranes. Similar effects were not observed when using ferric iron. Membranedamage was detected through irreversible increases in salt passage and the presenceof chloride on the membrane surface using energy-dispersive spectroscopy. Amechanistic study suggested that the formation of an amidogen radical (·NH<sub>2</sub>) duringNH<sub>2</sub>Cl decomposition with Fe(II) led to the reduction of the activation energy for thechlorination reaction to proceed using NH<sub>2</sub>Cl. Enhanced oxidation using HOCl andFe(II) may have resulted from the formation of ·OH radicals, which also lowered thechlorination-activation energy. Both pH suppression (from 8.0 to 6.0) and dechlorination(7.0 mg/L sodium sulfite) successfully halted the chlorination reaction. Includes 33 references, tables, figures.
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