pKa-directed acid modification of PEDOT:PSS membranes for efficient Pb(II) removal

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The widespread presence of Pb(II) in industrial wastewater poses serious risks to environmental security and public health. Conventional polymeric membranes often suffer from the permeability-selectivity trade-off, limiting their applicability in heavy metal treatment. In this study, an acid-induced reconstitution strategy for a conjugated polymer-based composite membrane (PEDOT:PSS@PVDF) is reported for efficient Pb(II) removal. By incorporating acids with different pK a values into the PEDOT:PSS matrix, the protonation degree was systematically modulated, triggering a structural transition from benzoid to quinoid configurations. This transition enhances π-electron delocalization along the polymer backbone, thereby improving the electron transport capability and strengthening the adsorption and reduction of Pb(II). Furthermore, the reconstructed membrane exhibits increased pore size and porosity, achieving a highly water permeance of up to 99.8 L m -2 h -1 bar -1 while maintaining the Pb(II) rejection rate of 98.3% under acidic conditions (pH = 2), thereby mitigating the trade-off effect within the acid series examined. This work presents a strategy for designing high-permeance, high-rejection membranes by regulating molecular conformation conjugation control, offering a potential route for treating heavy metal wastewater.