Effect of halides on polyamide-based membrane flux and monomer degradation during chloramination

Polyamide (PA)-based membranes are widely used in reverse osmosis (RO) and nanofiltration (NF) but can react with chlorine-based disinfectants (free chlorine chloramines) applied for biofouling control. This study examined how chloramines affected PA layer reactivity performance when individual mixed halides (Cl − , Br I ) were present, since these reactants form a host of different halogenating agents reactive species. Experiments measured membrane (SWC4-LD) via flux, surface chemistry using X-ray photoelectron spectroscopy (XPS), monomer (i.e. benzanilide (BA)) reactivity, under varied halide (0 to seawater range) pH (4–9) conditions. These experiments also compared other that chlorinated instead. Results indicated flux differentials the greatest after chlorination as chloramination or without Cl and/or implying was more detrimental polyamide structural integrity. The limited role supported by its low halogenation contrasted ability rapidly transform BA by-products. Mass transfer limitations within rigid 2-D polymer structure likely drove this disparity. Subsequent addition further lowered advanced transformation all conditions, whereas did not significantly impact monomer. As consequence, changes during highly dependent on type. Such observations intended inform may be reduce present RO- NF- feed waters. • Flux greater halides. alone played minimal chloramination. strong High decreased increased transformation. had effect