Improving the efficiency of polymer-based membranes for water treatment can be achieved through various modifications of their surface properties. These modifications can enhance the membrane's selectivity, permeability, and fouling resistance. Here are some strategies to consider:1. Surface grafting: Grafting hydrophilic polymers or functional groups onto the membrane surface can improve water permeability and reduce fouling. Examples of hydrophilic polymers include polyethylene glycol PEG , polyvinyl alcohol PVA , and polyacrylic acid PAA . Grafting can be performed through chemical reactions, such as free radical polymerization or click chemistry.2. Surface coating: Applying a thin layer of hydrophilic or fouling-resistant material onto the membrane surface can enhance its performance. Examples of coating materials include zwitterionic polymers, nanoparticles e.g., silver, titanium dioxide , and hydrogels. Coating methods include dip-coating, spin-coating, and layer-by-layer assembly.3. Surface patterning: Creating micro- or nano-scale patterns on the membrane surface can increase the surface area, enhance water flux, and reduce fouling. Patterning techniques include photolithography, soft lithography, and nanoimprint lithography.4. Surface roughness modification: Adjusting the surface roughness of the membrane can influence its fouling resistance. Generally, smoother surfaces are less prone to fouling. Surface roughness can be modified through techniques such as plasma treatment, chemical etching, or mechanical polishing.5. Surface charge modification: Altering the membrane's surface charge can affect its selectivity and fouling resistance. For example, introducing a negative charge on the surface can repel negatively charged foulants, such as organic matter and bacteria. Surface charge modification can be achieved through chemical reactions, such as the introduction of charged functional groups or the adsorption of charged nanoparticles.6. Blending with additives: Incorporating additives, such as hydrophilic polymers, nanoparticles, or antimicrobial agents, into the membrane material can improve its performance. These additives can be blended with the polymer during the membrane fabrication process.By implementing one or more of these strategies, the efficiency of polymer-based membranes for water treatment can be significantly improved. The choice of modification method will depend on the specific application, membrane material, and desired performance characteristics.