Novel electro-assisted TPPG separation membrane: Fabrication and separation performance for organic compounds and salts

Efficient separation of small-molecule organics (e.g., dyes, pharmaceuticals, peptides) and salt ions is critical for resource cycling and zero-liquid-discharge wastewater treatment. However, conventional pressure-driven membrane processes are limited by the ubiquitous permeability-selectivity trade-off and often suffer from inadequate fouling resistance. This study developed a self-entangled topological membrane with an irregularly interpenetrated network by physical mixing conductive polypyrrole-coated bacterial cellulose (PPy@BC) with polyvinyl alcohol (PVA), and then was stabilized with a glutaraldehyde (GA) crosslinking (denoted as TPPG). Using a self-designed electric field-coupled cross-flow setup, the TPPG membrane achieved an ultrahigh rejection ratio of 99.9 % for organic compounds (>250 Da), whereas almost zero rejection ratio ≤0.3 % for salt ions (mono-, di-, and trivalent). It should also be pointed out that this outstanding performance showed no decay even after 24 h or more of operation. Simultaneously, it delivered an exceptional water flux of ∼850 L m⁻² h⁻¹·bar⁻¹, surpassing most of commercial or literature-reported membranes by 1–2 orders of magnitude. Based on continuum modelling, the applied electric field (regardless of polarity) was revealed to be capable of enhancing confinement-induced concentration polarization and electrostatic repulsion within the TPPG's topological nanochannels by restructuring the double electrical layer. The transmembrane transport of salt ions was thereby accelerated, enabling their complete separation from organics. This work opens a new avenue for precise and highly efficient membrane based separation of small-molecule organics and salts.