Ultrafiltration ceramic membrane performance during the treatment of model solutions containing dye and salt

• An ultrafiltration ceramic membrane was used for the treatment of dye/salt mixtures.
• The influence of pressure and feed salt content on flux and retention was evaluated.
• The presence of salt in the feed solution reduced the efficiency of the process.
• Higher total resistance and lower dye rejection were obtained in the presence of NaCl.
• Membrane–solutes electrostatic interactions explained the observed behavior.

The present study reports the results of the ultrafiltration with a ceramic membrane of model solutions containing NaCl and a reactive dye, which simulate textile wastewaters. The effect of salt concentration (1, 2.5 and 4 g/L NaCl) and transmembrane pressure (1, 2, and 3 bar) on the evolution over time of both permeate flux and solutes rejection was tested. Membrane fouling was also investigated in terms of analysis of resistances-in-series, determining the contribution of both reversible and irreversible fouling under any condition tested. More severe flux decline and a slight reduction in color rejection were observed under higher pressure. Furthermore, it was demonstrated that the membrane performance was significantly worsened in the presence of salt, according to permeate flux, dye rejection and the values of the different resistances. Higher flux decline and total resistance together with lower color removal were observed when adding NaCl to the solution. These results were attributed to membrane charge and repulsion-attraction phenomena. It was then suggested that electrostatic interactions between the solutes and the membrane materials have an important role in the ultrafiltration performance, as well as influencing the kind of fouling affecting the membrane.