Enhanced organic dye rejection and anti-fouling performance of PVDF membranes: a comparative study of nano-ZrO ₂ sol and powder doping

Abstract In this study, zirconium dioxide (ZrO 2 ) nanofillers were incorporated into polyvinylidene fluoride (PVDF) membranes via DMF-induced phase inversion to systematically compare the effects of ZrO 2 in two physical forms—sol and powder—at loadings of 0.5–2.0 wt%. This work represents the first direct comparison of ZrO 2 sol and powder within the same PVDF matrix, providing mechanistic insight into how filler form governs dispersion, phase inversion behavior, and membrane performance. Comprehensive characterization (FTIR, XRD, SEM, porosity analysis, water contact angle, surface free energy, and tensile testing) revealed that both fillers induced partial α -to- β phase transformation and enhanced membrane hydrophilicity. At an optimal loading of 1.0 wt%, the water contact angle decreased from 80.5° (pristine PVDF) to 68.6° for powder-modified membranes and 70.2° for sol-modified membranes. SEM analysis showed that ZrO 2 powder produced a heterogeneous yet highly interconnected pore structure with an average pore size of 33.51 nm, whereas ZrO 2 sol yielded a smoother morphology with slightly larger pores (35.24 nm). As a result, the 1.0 wt% powder-modified membrane exhibited the most balanced performance, achieving high rejection rates for Neutral Red 5 (90.86%), Disperse Blue 79 (94.39%), and bovine serum albumin (96.80%), together with over 90% flux recovery and the highest BSA adsorption capacity (67.89 μg·cm −2 ). In contrast, the 2.0 wt% sol-modified membrane showed higher initial permeability (115.7 L·m −2 ·h −1 ) but reduced fouling resistance. Overall, these results demonstrate that the physical form of ZrO 2 critically determines dispersion uniformity, interfacial interactions, and phase inversion kinetics, enabling rational design of high-performance nanocomposite PVDF membranes for advanced wastewater treatment.