In this study, polyvinylidene fluoride (PVDF) nanocomposite membranes modified with hydrophobic nano-silica (SiO2-SA) were developed for desalination via membrane distillation (MD). SiO2 nanoparticles were modified with stearic acid (SA) via a simple, cost-effective, and environmentally friendly method to enhance their hydrophobicity before being incorporated into the PVDF matrix. The influence of SiO 2-SA concentration on membrane properties, including morphology, porosity, surface roughness, hydrophobicity, mechanical strength and liquid entry pressure (LEPw), was investigated. Furthermore, the impact of various feed compositions on the LEP was also evaluated to better understand membrane resistance under different operating conditions. Optimal membrane performance was achieved with the incorporation of 2 wt.% SiO2-SA, which led to enhanced porosity and surface roughness, a water contact angle of 94.6°, and a maximum LEPw of 4.5 bar. In direct contact membrane distillation (DCMD) with a 3.5 wt.% NaCl feed solution, the PVDF/2% SiO2-SA membrane exhibited high water flux of 8.11 kg/m2 h—five times that of pristine PVDF—along with excellent salt rejection (> 99.9%) and low permeate conductivity. Wetting resistance of the membranes was further assessed by introducing sodium dodecyl sulfate (SDS) into the feed solution. Additionally, fouling behavior was evaluated using a saline solution containing 3.5 wt.% NaCl and 1 g/L canola oil. The PVDF/2% SiO2-SA membrane exhibited stable flux under these conditions, demonstrating its superior resistance to fouling and wetting. Moreover, a 24-h longterm DCMD test confirmed the stability and durability of the optimized membrane, with consistent flux and high salt rejection throughout the operation. These findings highlight the potential of SiO2-SA modified PVDF membranes in reducing wetting, mitigating fouling, and enhancing desalination efficiency, offering a promising approach for advanced MD applications.

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