Hydration-Dependent Transport and Condensed Tannin Incorporation in Cellulose and Polypropylene Fibrous Microfiltration Membranes

Cellulose (FCm) and polypropylene (PPm) fibrous microfiltration membranes with comparable dry-state porosities were compared in terms of wettability, hydration, effective porous structure, and pressure-driven water transport. FCm exhibited substantially greater water uptake than PPm. A parametric volume-balance analysis showed that the inferred hydrated porosity and model-dependent tortuosity of FCm were highly sensitive to the assumed allocation of retained water, preventing the assignment of unique hydrated-state structural values. FCm displayed an approximately Darcy-like pressure–flux response, whereas PPm exhibited nonlinear behavior over 8.5–33.8 kPa, consistent with a pre-Darcy regime. Condensed-tannin (TAM) incorporation was subsequently evaluated as a separate hydroalcoholic membrane-modification process. At a fixed contact time of 120 min and 8.0% (w/v) TAM, incorporation reached 9.90 ± 0.72% for FCm and 8.64 ± 1.64% for PPm. Gompertz analysis showed that operational stabilization depended on membrane type and TAM concentration; thus, 120 min did not represent a universal equilibrium condition. TAM incorporation also increased with temperature and exhibited substrate-dependent pH behavior. Spectroscopic and microscopic analyses supported the deposition of a polyphenolic phase, while aqueous washing revealed partial release of non-crosslinked TAM. Overall, comparable dry-state porosity did not imply equivalent aqueous hydraulic behavior, and TAM incorporation depended additionally on substrate chemistry and processing conditions.