Threshold flux and limiting flux for micellar enhanced ultrafiltration as affected by feed water: experimental and modeling studies

Micellar enhanced ultrafiltration is a promising technology for removing trace amounts of organic pollutants in wastewater, but membrane fouling caused by Gemini micelles is a significant problem restricting its industrial application. In this study, a flat sheet ultrafiltration membrane with four types of Gemini surfactant systems and various feed concentrations was used to treat phenol wastewater, while the flux behavior and fouling mechanism were investigated. The optimal permeate flux of phenol decreased in the sequence as follows: CG12 > CG16 > CG12 − Brij35 > CG16 − Brij35. In order to study the rate of membrane fouling, a developed liner regression method was utilized to help determine the threshold flux, as well the degree of concentration polarization and membrane fouling. Furthermore, limiting flux was investigated to avoid extensive cake layer formation. Threshold flux and limiting flux strongly depended on the feed concentration and the type of micelles. The threshold flux reduced gradually with feed concentration, due to the increased fouling rate and presence of irreversible fouling. Owing to the effect of charge density and hydrophobicity of micelles, CG12 exhibited the highest threshold flux and limiting flux. Flux-TMP relation was divided into three regions for analyzing the corresponding changes of permeate flux, filtration resistance and conceptual particle deposition model. Besides, fouling mechanism of MEUF was discussed. This study provides a guideline for analyzing membrane fouling and seeking an optimum operation strategy for controlling fouling in membrane water treatment.