Advances in Silver-Reinforced Polysulfone Nanocomposite Membranes for Water Treatment Applications

Polymeric membranes are widely recognized as highly effective materials for water treatment and separation; however, membrane fouling, particularly biofouling, remains a significant limitation to their long-term performance [۱]. Polysulfone (PSF) is one of the most commonly used materials for membrane fabrication due to its excellent thermal and mechanical stability, chemical resistance, and ease of processing. Nevertheless, its inherently hydrophobic nature promotes the adsorption of proteins and bacteria, leading to undesirable biofilm formation on the membrane surface. Therefore, enhancing hydrophilicity and imparting durable anti-fouling functionality to PSF membranes is essential. In recent years, silver nanoparticles (AgNPs) have been introduced as effective additives for polymeric membrane modification because of their strong antimicrobial activity and favorable stability. However, challenges such as nanoparticle agglomeration, non-uniform distribution, and reduced surface porosity continue to limit their full potential [۱,۲]. Sacrificial alkaline layers can play a crucial role in increasing surface charge and improving hydrophilicity, but they lack the stability required to reliably inhibit biofouling. In this study, with the aim of developing a highly efficient PSF membrane reinforced with AgNPs, multiple strategies were systematically reviewed to optimize sacrificial layer selection, nanoparticle immobilization techniques, and membrane composition. Previous studies have shown that using a polydopamine (PDA) layer, owing to its strong adhesion characteristics and its ability to form covalent bonds, is one of the most reliable approaches for AgNP immobilization [۳]. The results further indicated that excessive PDA thickness reduces porosity and increases resistance to water flux; therefore, a thinner PDA layer provides improved performance. To mitigate nanoparticle aggregation and enhance stability, prior research demonstrates that in-situ synthesis enables more uniform AgNP distribution and improved interaction within the PSF matrix [۳,۴]. Unlike ex-situ loading, the application of monomers facilitates simultaneous in-situ grafting of silver nanoparticles and polymer chains, resulting in a more homogeneous nanoparticle distribution throughout the membrane. The reduced mobility of monomers increases the glass transition temperature (Tg) and strengthens the interactions between PSF chains and AgNPs. Moreover, uniform AgNP dispersion significantly improves the antimicrobial performance of the membrane. For further stabilization, polyvinylpyrrolidone (PVP) has been proposed as an effective reducing and stabilizing agent, with an optimal concentration of ۵% reported to yield the best results [۵]. Based on a comprehensive review of existing literature, the highest membrane performance has been achieved in PSF membranes reinforced with AgNPs, fabricated using a thin PDA layer combined with an in-situ synthesis method. This structure promotes uniform nanoparticle dispersion, enhances mechanical stability, and substantially strengthens antimicrobial activity. The use of PVP as a stabilizer, together with precise control of PDA layer thickness, improves water flux, increases membrane resistance, and reduces biofouling [۳,۴]. Despite these advancements, several key parameters for optimizing AgNP-modified PSF membranes remain insufficiently investigated. Controlling silver-ion release and preventing membrane degradation are critical challenges, as both strongly influence nanoparticle retention and long-term durability. Furthermore, the choice of barrier layer significantly affects membrane aging behavior; therefore, selecting a layer that provides effective nanoparticle immobilization, improved mechanical strength, and preserved porosity is essential. In addition, preventing AgNP agglomeration requires careful consideration of nanoparticle morphology and the choice of stabilizing agent. Collectively, these factors influence the: ⚫Uniform distribution of nanoparticles ⚫Prevention of agglomeration •Mechanical stability of the membrane • Preservation of membrane porosity Control of silver-ion release rate These parameters have not yet been fully optimized, leaving a critical knowledge gap that limits the design of membranes capable of delivering long-term, stable performance under real water-treatment conditions.

کلیدواژه ها:

Silver nanoparticles ، Polysulfone membranes ، Biofouling ، Surface modification ، Water flux ، Antimicrobial membranes