Taguchi–Grey Relational Optimization of Polysulfone-Based Composite Hollow Fiber Membranes for Urea Removal in Dialysis

• Increasing the air gap increases the porosity of hollow fiber membranes. • Increasing the dope extrusion rate decreases the inner diameter of the hollow fiber membrane. • Metal oxides have metal cations, oxygen anions, and surface –OH groups that enhance hydrophilicity in polymeric membranes. • α-Fe 2 O 3 /GO composite in polysulfone significantly enhanced urea removal in a short-term lab-scale membrane system over the pristine polysulfone membrane. In this work, hollow fiber polysulfone (PSf)-based membranes were fabricated, and their urea removal performance was enhanced by precise control of porosity and the incorporation of nanocomposite particles into the membrane matrix. To achieve this, nanocomposite particles consisting of α-Fe 2 O 3 and graphene oxide (GO) with varying weight ratios (9:1, 8:2, 6:4, and 1:1) were initially synthesized and then incorporated into flat-sheet membranes. The surface properties of the composite membranes were characterized by zeta potential, water contact angle (WCA) measurements, and scanning electron microscopy (SEM). Composite hollow fiber membranes (HFMs) were then prepared by incorporating an α-Fe 2 O 3 /GO ratio of 8:2, which resulted in the lowest WCA of 36.55° ± 1.7°. The effects of process factors—including air gap distance, bore fluid flow rate, dope extrusion rate, and the concentration of α-Fe 2 O 3 /GO nanocomposite particles in the polymer—on the inner diameter and porosity of HFMs were analyzed using Taguchi–Grey relational analysis (GRA). The composite HFMs fabricated under the identified optimal conditions—characterized by minimum inner diameter and maximum porosity—showed a higher pure water permeability (PWP) of 205.39 ± 4.95 L m −2 h −1 bar −1 compared with the pristine PSf membrane, which had a PWP of 116.33 ± 4 L m −2 h −1 bar −1 . In addition, the optimized samples demonstrated a urea removal of 58.33 ± 1.6% in a short-term lab-scale membrane system, compared with 21.57 ± 3.83% for the pristine polysulfone HFMs. These findings provide a foundation for future studies on the potential of these HFMs in biomedical applications.