Asymmetric NH2-MWCNTs/PES ultrafiltration membranes were prepared via phase inversion induced by immersion precipitation [49] using casting solutions involving PES (14 wt.%), PVP (2 wt.%) and proper amount of functionalized MWCNTs in DMAc as solvent. Precise amount of functionalized MWCNTs (0.05, 0.1 and 1 wt.%) was mixed into DMAc and well dispersed by sonication for 30 min to improve the homogeneity. Note that membranes marked as 0.1 wt.% NH2-MWCNTs refer to membranes prepared in a casting solution in which the amount of the NH2-MWCNTs with respect to PES+DMAC was 0.1 wt.%. After dispersing NH2-MWCNTs in solvent, dried PES and PVP were dissolved in the dope solution by continuous stirring for 24 h. PVP was added as a porogen to elevate the yield of pores in the coagulation process. The resultant homogeneous polymer solution was again sonicated for 10 min to remove air bubbles and well dispersing of the nanoparticles in the PES matrix. Solvent loss by evaporation was insignificant due to the high boiling points of DMAc (164–166 °C). Then, the solution was sprinkled and cast using self-made casting knife with 250 μm thickness over a clean glass plate. Next, the glass plate was immediately moved to the non-solvent bath (distilled water at 25 °C) to precipitate the polymer and form asymmetric porous membranes. After primary phase separation, the formed membranes were stored in fresh distilled water for 24 h to guarantee the complete phase inversion. Finally, the membranes were sandwiched between two filter paper sheets for 24 h at the room temperature to be dried.