Separation of anionic surfactants on ultrafiltration membranes

The objective of this study was to investigate the influence of MWCO, pressure, SDS concentration, salt amount and temperature on surfactant removal and permeate flux. Intersep Nadir membranes made from polyethersulphone (PES) and polysulphone (PS) were used. With the addition of a mineral salt to the SDS solution, a dramatic decrease in retention of SDS was observed. There was no discernible effect on the retention coefficient of the membranes with the increase in the amount of the mineral salt added to the SDS solution. The volume flux was slightly dependent on the ionic concentration in the feed solution: high ion concentration caused a small decrease of the water flux. The effect of pressure on the separation efficiency for the PES and PS membranes was evaluated; it produced only a small reduction in the retention as the pressure was increased. With the increase of temperature of SDS solutions, a decrease in the retention of SDS was observed. The permeate flux increased with temperature due to the solution viscosity decrease.

The following conclusions can be deduced based on the experimental investigation: C A decrease in retention of SDS for the PES and PS membranes with addition of a mineral salt (Na2SO4, NaCl, NaH2PO4@H2O) was observed. C No discernible effect on the retention coefficient of the membranes was found as the mineral salt dosage was increased. The greates drop in SDS retention was observed at the lowest concentration of mineral salt used for all tested membranes. This phenomenon is more pronounced for Na2SO4 than for NaCl and NaH2PO4@H2O. C A small reduction of volume flux was observed with an increase in the concentration of mineral salt in case of low MWCO membranes. For 30 kDa membranes the decrease in volume flux was more pronounced. C With the increase of temperature of SDS solutions, a small decrease in the retention of SDS was observed. The permeate flux increased with temperature due to the solution viscosity decrease and thermal expansion of the membrane material.