Ultrafiltration of dye solutions in the presence of cationic and anionic surfactants

The objective of the study was to investigate the influence of surfactant in model dye solutions on the ultrafiltration efficiency. The anionic detergent (sodium dodecyl sulphate (SDS)) and cationic detergent (hexadecyltrimethylammonium bromide (CTAB)) were added to the dye solutions. Three anionic organic dyes of molecular weights ranging from 327 to 1060 Da were applied. Intersep Nadir membranes made of polyethersulfone and regenerated cellulose were used in the experiments. The operation pressure varied from 0.1 to 0.20 MPa. The concentration of dyes in model solutions was equal to 100 g/m3, whereas surfactant dosage amounted to 0.1, 0.6 and 1.0 CMC (critical micelle concentration). The experiments revealed dye retention by surfactant present in experimental solutions was strongly affected by the nature of detergent, membrane material and membrane cut-off value. It was also found that the presence of an anionic surfactant brought about the worsening of separation factor, whereas the cationic surfactant improved dye rejection.