Abstract
The development of sophisticated and sustainable water treatment systems has become necessary due to the growing contamination of water resources by mercury and other heavy metal ions. This review examines current advances in composite membrane systems, with a special emphasis on polymer-based and functionalized membranes for efficient metal ion removal. Polymer matrix composites, such as polyvinylamine-enhanced ultrafiltration and ligand-functionalized membranes, improve selectivity and adsorption capacity by including active functional groups. Furthermore, the incorporation of sophisticated materials such as metal-organic frameworks, covalent organic frameworks, and two-dimensional nanomaterials has greatly improved membrane performance by increasing surface area, variable porosity, and multifunctionality. The review decisively explores the essential mechanisms driving separation, such as size exclusion, electrostatic interactions, and ion exchange. These mechanisms work in concert to achieve exceptional removal efficiency and selectivity. Ultimately, the integration of polymer matrices with functional and nanostructured materials represents a powerful strategy for the development of next-generation membranes designed for sustainable and high-performance aqueous systems.