Removal of Phenol from Wastewater Using Micellar-Enhanced Ultrafiltration with Quaternary Ammonium Salt Cationic Gemini Surfactants

Micellar-enhanced ultrafiltration (MEUF) as a surfactant-based separation process is promising for the treatment of low concentration organic wastewater. Gemini surfactant becomes the focus of the field of MEUF increasingly due to its excellent performance in MEUF. In order to investigate the effect of operational factors on the effectiveness of MEUF process, quaternary ammonium salt Gemini surfactants were used for the removal of phenol. The critical micelle concentration (CMC) values of cationic gemini surfactants (CG12, CG14, and CG16) were analyzed. Then the influence of various factors, include CG concentration, phenol concentration, electrolyte concentration and operating pressure, on the removal performance was investigated. Finally, BBD experimental design was carried out to identify optimal operational conditions. The results showed that hydrophobic chain length of Gemini surfactant s have significant effect on its CMC value and the MEUF process. The longer the hydrophobic chain length, the higher phenol rejection. However, it can result in membrane fouling. CG concentration has significant influence on phenol rejection and permeation flux. And phenol concentration has a direct impact on its removal. In addition, the optimal operational condition is that CG12 concentration at 10 CMC, phenol concentration at 1 mM, and NaCl concentration at 25 mM. The corresponding optimal phenol rejection is 91.16%, the optimal permeate flux is 29.33 L/m2 h.