Reverse osmosis membrane composition, structure and performance modification by bisulphite, iron(III), bromide and chlorite exposure

Reverse osmosis (RO) membrane exposure to bisulphite, chlorite, bromide and iron(III) was assessed in terms of membrane composition, structure and performance. Membrane composition was determined by Rutherford backscattering spectrometry (RBS) and membrane performance was assessed by water and chloride permeation, using a modified version of the solution-diffusion model. Iron(III) dosage in presence of bisulphite led to an autooxidation of the latter, probably generating free radicals which damaged the membrane. It comprised a significant raise in chloride passage (chloride permeation coefficient increased 5.3–5.1 fold compared to the virgin membrane under the conditions studied) rapidly. No major differences in terms of water permeability and membrane composition were observed. Nevertheless, an increase in the size of the network pores, and a raise in the fraction of aggregate pores of the polyamide (PA) layer were identified, but no amide bond cleavage was observed. These structural changes were therefore, in accordance with the transport properties observed. [Display omitted] •Bisulphite and Fe(III) caused an increased chloride passage in RO membranes.•Bisulphite, Fe(III) and chlorite modified the membrane pore size distribution.•In Fe(III) presence, bisulphite in excess to chlorite led to greater chloride passage.•Chlorite in excess to bisulphite caused RO membrane chlorination.•Bisulphite, Fe(III), chlorite (in excess) and bromide led to membrane bromination.