Comparative evaluation of metal, metal oxide, and bimetallic nanoparticles in water treatment applications
Abstract
The rapid increase in global water pollution resulting from industrialization, urbanization, intensive agriculture, and emerging contaminants has highlighted the limitations of conventional water treatment technologies, creating an urgent need for efficient and sustainable remediation strategies. Nanotechnology has emerged as a promising solution owing to the unique physicochemical properties of engineered nanoparticles, including high specific surface area, tunable surface chemistry, and superior catalytic activity. This review presents a comprehensive comparative evaluation of metal nanoparticles (MNPs), metal oxide nanoparticles (MONPs), and bimetallic nanoparticles (BNPs) for water and wastewater treatment. Their synthesis methods, physicochemical characteristics, contaminant removal mechanisms, environmental applications, operational performance, and limitations are critically assessed. Metal nanoparticles exhibit excellent reductive and antimicrobial properties, metal oxide nanoparticles provide superior photocatalytic activity and magnetic recoverability, whereas bimetallic nanoparticles offer enhanced catalytic efficiency and pollutant selectivity through synergistic effects. The review further discusses the removal of heavy metals, dyes, pharmaceuticals, pathogens, and emerging contaminants, together with advances in pilot‐scale applications, permeable reactive barriers, and continuous‐flow treatment systems. Environmental transformations, nanotoxicity, bioaccumulation, and regulatory considerations are also examined within the framework of current international guidelines. Finally, key challenges associated with large‐scale production, long‐term stability, environmental safety, and commercialization are highlighted, while future perspectives emphasize green synthesis, safety‐by‐design nanomaterials, hybrid treatment systems, and regulatory harmonization. Overall, this review provides a practical framework for selecting nanoparticle systems based on contaminant characteristics, treatment objectives, operational requirements, and sustainability considerations, thereby supporting the development of next‐generation water purification technologies.