AbstractA new low‐cost composite ultrafiltration membrane made of polysulfone (PSf) and polystyrene (PS) blend was effectively achieved on the ceramic pozzolan support using dip‐coating method. The effect of PS content (5–20 wt%) on membrane properties such as microstructure and filtration performances was investigated. The Fourier‐transform infrared spectroscopy, nuclear magnetic resonance, and differential scanning calorimetry analyses confirm that the two polymers lead to physical blend. The morphology analysis shows that PSf/PS membrane layer is homogeneous and strongly adherent on the pozzolan support. Furthermore, the developed membrane was applied for filtration of direct red (DR80) and methyl orange (MO) solutions at a pressure of 3 bar. It was proven that the PS addition significantly enhances the rejection of the membrane companying with a decrease of permeate flux to meet the trade‐off selectivity‐permeability. The optimized PSf/PS membrane containing 5 wt% of PS has a water permeability of 24 L h−1 m−2 bar−1, and could reject 91% and 76%, respectively for DR80 and MO. Beside the promising filtration results, the developed membrane is also low‐cost thanks to using pozzolan support, and it could be consequently scaled up for the treatment of colored wastewater generated from textile industries.