Performance comparison of nano-Al₂O₃-modified PVDF membranes fabricated via two methods for enhanced dye removal

Improving the contamination resistance of polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes against organic dyes is essential for efficient dye wastewater treatment. In this work, PVDF membranes were prepared using a phase separation method via two separate processes (one utilizing Al₂O₃ sol and the other utilizing nano-Al₂O₃ powder-modified PVDF UF membranes), and their anti-pollution ability and enhanced hydrophilicity were evaluated. The effects of the varying content of Al₂O₃ nanoparticles on the microstructure of PVDF membrane were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). Compared to 1.0 wt% Al₂O₃ powder, the modification impact of 20% Al₂O₃ sol on the overall performance of the membrane was superior. It was demonstrated that the pore size and mechanical strength of the modified membranes were notably better than those of the pure PVDF membrane and the water flux also increased from 148.80 L m^-2 h^-1 to 217.00 L m^-2 h^-1. An efficient and economical membrane separation method was essential for the treatment of dye wastewater, and the dye filtration experiments revealed that the filtration and antifouling properties of the modified PVDF membranes were significantly improved. The retention rate of Al₂O₃/PVDF-modified membranes for neutral red 5 (NR 5) and dispersed navy blue 79 (DB 79) was more than 96%. After three filtration cycles, the recovery rates of NR 5, DB 79, and bovine serum albumin (BSA) flux were 94.67%, 92.54%, and 95.55%, respectively. These results show that the Al₂O₃/PVDF-modified membranes can cope with more complex wastewater treatment environments.