Highly chlorine-resistant multilayer reverse osmosis membranes based on sulfonated poly(arylene ether sulfone) and poly(vinyl alcohol)

• Novel TFC RO membranes were obtained by coating SPAES-C on a microporous polysulfone support.
• A secondary cross-linked PVA layer was coated on the top of SPAES-C layer to improve the NaCl rejection.
• After cross-linking, the NaCl rejection increased from 91.2% to 96.8%.
• The multilayer RO membranes showed good chlorine-tolerance.

Sulfonated cardo poly(arylene ether sulfone) copolymers (SPAES-C) were synthesized via post-sulfonation of the parent polymer. A series of reverse osmosis composite membranes were obtained by coating SPAES-C on porous polysulfone support membranes, with varying the concentration of coating solutions. The SEM results indicated that the obtained reverse osmosis membranes had smooth surface, and no defect was observed. Meanwhile, the functional layer thickness obtained from the SEM results was in the range from 300 to 400 nm. All the resulting membranes showed good water flux and appropriate NaCl rejection. In order to improve the NaCl rejection, a secondary layer of formaldehyde-cross-linked polyvinyl alcohol was coated on the surface of SPAES-C membrane, and this layer could improve NaCl rejection from 91.2% to 96.8% without a serious loss of water permeability. Compared with commercial PA reverse osmosis membrane, the composite membranes based on SPAES-C showed excellent chlorine-tolerance in reverse osmosis operation.