Improving the selectivity and permeability properties of polymer-based membranes for water treatment can be achieved through various strategies. These strategies aim to enhance the membrane's ability to remove specific contaminants such as heavy metals or organic pollutants while maintaining high water permeability. Here are some approaches to consider:1. Surface modification: Altering the surface properties of the membrane can improve its selectivity and permeability. This can be done through techniques such as grafting, coating, or plasma treatment. For example, grafting hydrophilic functional groups onto the membrane surface can enhance its affinity for water and repel organic pollutants.2. Incorporation of functional materials: Introducing materials with specific affinity for target contaminants can improve the membrane's selectivity. Examples include incorporating metal-organic frameworks MOFs , zeolites, or nanoparticles with high adsorption capacity for heavy metals or organic pollutants. These materials can be embedded within the polymer matrix or coated onto the membrane surface.3. Pore size control: Controlling the pore size and distribution of the membrane can enhance its selectivity. This can be achieved through techniques such as phase inversion, electrospinning, or interfacial polymerization. By creating a membrane with smaller pores or a more uniform pore size distribution, the removal of specific contaminants can be improved.4. Membrane thickness optimization: Adjusting the thickness of the membrane can influence its permeability and selectivity. Thinner membranes generally have higher permeability but may compromise selectivity. Therefore, optimizing the membrane thickness to balance these properties is crucial.5. Crosslinking: Crosslinking the polymer chains can improve the membrane's mechanical and chemical stability, as well as its resistance to fouling. This can be achieved through chemical crosslinking agents or UV-induced crosslinking. Crosslinked membranes may exhibit enhanced selectivity and permeability due to their improved structural integrity.6. Blending polymers: Combining two or more polymers with complementary properties can result in a membrane with improved selectivity and permeability. For example, blending a hydrophilic polymer with a hydrophobic polymer can enhance the membrane's water permeability while maintaining its ability to reject organic pollutants.7. Designing multilayer membranes: Constructing membranes with multiple layers, each with specific properties, can improve overall performance. For instance, a thin selective layer can be deposited onto a porous support layer, combining the high selectivity of the thin layer with the high permeability of the support layer.8. Membrane post-treatment: Post-treatment processes such as annealing, solvent extraction, or chemical treatment can further improve the membrane's selectivity and permeability. These treatments can alter the membrane's pore structure, surface properties, or chemical composition to enhance its performance.By employing these strategies, it is possible to develop polymer-based membranes with improved selectivity and permeability properties for water treatment applications, particularly in removing specific contaminants such as heavy metals or organic pollutants.