Fabrication of a High-flux Sulfonated Polyamide Nanofiltration Membrane: Experimental and Dissipative Particle Dynamics Studies

Novel high-flux thin film composite (TFC) nanofiltration (NF) membranes were fabricated via interfacial polymerization (IP) on a polysulfone substrate using 2,2′-benzidinedisulfonic acid (BDSA) as the amine monomer in aqueous solution. The intrinsic resistance of the resulting membranes (Rm) was found to be as low as 2.37×1013m−1, indicating a considerably low tolerance against hydraulic resistance. The optimized membrane TFC-1.0 showed excellent rejection towards different inorganic electrolyte solutions in the following order: Na2SO4>NaCl>MgCl2>CuSO4>MgSO4, indicating the negatively charged nature of the membrane. Surface properties were evaluated by field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and contact angle measurements, and the results indicated a smooth and moderately hydrophobic surface. Using dissipative particle dynamics (DPD), the coarse-grained model molecules at the mesoscale level were used to establish an oil-water interface model with regard to the current IP process. The orientation of BDSA monomers was studied and it was found that most of the sulfonic acid groups were facing towards the aqueous solution, while the outer faces were covered by the nanoaggregates of the rigid polymer backbones. This finding is consistent with the observed experimental results and provides a reasonable explanation for the surface properties. The NF membrane has a high water permeability of 16.6Lm−2h−1bar−1 and high rejection ability for inorganic salts and organic solutes. These results confirm the suitability of this membrane for various applications, such as desalination and dye removal from wastewater.