Design of a monolithic cellulose Janus-like membrane for oil/water separation

Janus membranes offer a good solution for oil/water mixtures due to their opposite wettability, but existing designs often suffer from limitations arising from complex, resource-intensive fabrication procedures. This study proposes a cellulose-based monolithic Janus-like membrane prepared by non-solvent-induced phase separation (NIPS) from cellulose acetate followed by alkaline deacetylation and unilateral silanization (TEOS/MTES). The resulting membrane exhibits asymmetric wettability (hydrophobic: 91°, hydrophilic: ~0°). Structural and chemical characterization (SEM, EDS, FTIR, and BET/BJH) confirms the formation of a siloxane-containing surface layer, the integrity of the cellulose network, and a distribution of the pores toward the nanoscale, with a specific surface area of 26.9 m²/g. Gravitational peanut oil/water tests reveal high fluxes (3300-5527 Lm^-2h^- 1) with an apparent volumetric oil-retention efficiency of up to 95%, while for water/hexane, the apparent volumetric oil-retention efficiency reached 96.93% with a flux of 3950.62 Lm^-2h^- 1. The membrane retains excellent mechanical robustness (3.50 MPa), with a breaking force of 5.23 N, withstanding repeated deformations including axial rolling, compression, and bending, without cracking or delamination. This Janus-like membrane mimics the properties of Janus membranes while relying on a simplified, energy-efficient, and environmentally friendly fabrication strategy, and could represent a promising option for efficient, sustainable, and high-performance oil/water separation.