Influence of Ag Nanoparticle Loading on Dye and Salt Removal Efficiency of Graphene Oxide Membranes
Nano-engineered materials, particularly two-dimensional (2D) nanomaterials and advanced desalination membranes, are poised to play a transformative role in addressing global water scarcity through efficient purification technologies. Among these, graphene oxide (GO)-based nanofiltration membranes have emerged as promising candidates due to their high mechanical strength, tunable surface chemistry, and exceptional molecular sieving properties. However, despite these advantages, the practical deployment of GO membranes in aqueous environments is hindered by critical limitations, most notably, structural swelling and interlayer expansion due to water intercalation. This phenomenon compromises the long-term selectivity and ion/dye rejection performance of the membranes. To mitigate these drawbacks, the incorporation of nanoparticles such as silver nanoparticles (Ag NPs) has been explored to enhance membrane stability, reduce swelling, and improve overall filtration efficiency. Ag NPs not only stabilize the GO structure through interlayer interactions but also contribute antimicrobial and fouling-resistant properties, making them ideal candidates for wastewater treatment applications. While numerous studies have demonstrated the performance enhancement of GO membranes upon Ag NP incorporation, a systematic understanding of how Ag NP concentration affects rejection performance, particularly for organic dyes, remains incomplete. This research aims to address that gap by investigating the role of Ag NP loading concentration on the structural and functional properties of GO membranes. GO–Ag NP composite membranes were fabricated on polyether sulfone (PES) substrates via vacuum-assisted filtration, utilizing a series of Ag NP loadings to evaluate their influence on nanofiltration performance. A comprehensive suite of characterization techniques was employed: X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to assess changes in interlayer spacing (d-spacing) and pore morphology; UV-VIS spectroscopy was used to quantify dye concentrations in the feed and permeate, enabling calculation of rejection efficiency; Fourier-transform infrared spectroscopy (FTIR) provided insight into chemical interactions between Ag NPs and GO functional groups; contact angle measurements via a Ramé-Hart goniometer quantified surface wettability, while dead-end filtration experiments evaluated salt and dye rejection behavior. The results revealed that Ag NP concentration modulates the pore size and interfacial properties of the GO membrane, directly impacting its permeability and selectivity. Increased Ag NP content led to changes in hydrophilicity and d-spacing, influencing both the water transport rate and the membrane's ability to reject charged and neutral species. This study identifies optimal nanoparticle loading conditions that balance flux and rejection efficiency, offering a pathway for designing GO-based nanofiltration membranes with tailored performance for specific wastewater treatment scenarios.
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