Preparation of a hollow fiber composite membrane via synergistic integration of PSS-doped polypyrrole and electrostatic self-assembly

Doping-electrostatic self-assembly strategy for polypyrrole membranes. • PSS doping increases chain spacing and enhances pure water permeance. • The PDDA/PSS polyelectrolyte interlayer suppresses random agglomeration of pyrrole. • The membrane achieves over 99% dye rejection with NaCl rejection below 10%. To address the challenge of balancing high dye rejection and high salt permeation in polypyrrole (PPy) composite membranes for dye/salt separation, this study proposes a synergistic regulation strategy combining doping and electrostatic self-assembly to fabricate a multilayer composite membrane. Using a polyethersulfone (PES) hollow fiber membrane as the substrate, the first separation layer was constructed via in-situ polymerization of pyrrole doped with poly (sodium 4-styrenesulfonate) (PSS). Subsequently, a polydiallyldimethylammonium chloride (PDDA) interlayer was introduced by electrostatic self-assembly, followed by a second in-situ polymerization of PSS-doped pyrrole, yielding the PDDA/PSS-PPy₂@PES composite membrane. The results show that PSS doping enhances permeate flux, while the introduction of the PDDA interlayer and the second polymerization improves rejection. The electrostatic self-assembly between PDDA and PSS suppresses random aggregation of polypyrrole and promotes the formation of a loose, continuous separation layer. The optimized composite membrane exhibits a pure water permeance of 72.5 L·m −2 ·h −1 ·bar −1 , and rejection rates of 99.99% for Congo Red (CR), Eriochrome Black T (EBT), and Direct Red 23 (DR23), and 99.27% for Methyl Blue (MB). In the CR/NaCl mixed system, the rejection of CR exceeds 99.99%, while that of NaCl is only 9.4%, demonstrating excellent dye/salt selective separation performance. This work provides a feasible route for tailoring the structure and performance of polypyrrole-based composite membranes via synergistic doping-electrostatic self-assembly , showing promising potential in the treatment of printing and dyeing wastewater and the dyes resource recovery. Download: Download high-res image (64KB) Download: Download full-size image