Surfactant removal from water solutions by means of ultrafiltration and ion-exchange

The aim of the study was to compare the removal efficiency of anionic surfactant (belonging to alkylbenzenesulfonate family) from water solutions by means of ultrafiltration and ion-exchange. During the first stage of the experiments, the influence of surfactant type and its concentration, membrane cut-off and polymer material on ultrafiltration performance was evaluated. The next stage of the study was focused on effectiveness of ion-exchange using MIEX resin as a method of surfactant removal from water solutions. The effect of pollutant concentration, resin dose, mixing time, pH of the solution and mineral salt presence was assessed. It was noticed that the ultrafiltration separation of surfactant was significantly influenced by membrane material. The best separation characteristics were achieved by polysulfone and polyethersulfone membranes. The PES5 and PS5 ones allowed lower the surfactant concentration to be achieved ranging from 71 to 91% and from 55 to 81% for 5 kDa and 10 kDa. High surfactant retention was obtained at lower concentrations. With the increase in surfactant concentration the retention values decreased with a slight increase in CMC value. From the experimental investigation, the magnetic ion-exchange resin was found to be very effective in anionic surfactant removal in a wide range of concentrations. As well as the ion-exchange process was shown to be insensitive to the pH value of the solution and the mineral salt presence.

The experimental investigation demonstrated that the ultrafiltration separation of surfactant was significantly influenced by membrane material. The best separation characteristics were achieved by polysulfone and polyethersulfone membranes. High surfactant retention was obtained at low concentrations. With the increase in surfactant concentration the retention values decreased and again slightly increased above CMC value. The experimental process showed that the magnetic ion-exchange resin was found to be very effective in anionic surfactant removal. The high separation efficiency of anionic surfactant from model solutions in a wide range of concentrations was observed. At the same time the ion-exchange process was insensitive to the pH value of the solution and the mineral salt presence. From the results obtained it can be confirmed that the ion-exchange (with MIEX resin) can be effectively applied as an additional post-treatment process to remove the residual amounts of surfactants after ultrafiltration treatment in order to meet more stringent legislative requirements in the discharge detergent wastewater to the sewage system or to environment.