Biomimetic mineralization of nacre-inspired multiple crosslinked PVA/CaAlg/SiO2 membrane with simultaneously enhanced mechanical and separation properties.

Inspired by the natural nacre structure, we propose a new strategy to fabricate mineralized, multiple crosslinked hydrogel membranes with the "rigid silica in soft polymer" nacre-like structure. In-situ SiO2 nanoparticles (NPs) and polyvinyl alcohol/sodium alginate (PVA/NaAlg) are used to simulate the rigid "bricks" and soft "mortar" compositions of nacre, respectively. The nacre-like mineralized (PVA/CaAlg/SiO2) membrane showed a higher tensile strength of 4.1 ± 0.08 MPa, excellent pure water flux of 170 ± 3 L/m2h, and an oil/water rejection rate of 99 %. The interwoven hierarchal structure, similar to nacre, was determined by SEM analysis. In addition, incorporating SiO2 NPs increases the anti-swelling, roughness, and hydrophilicity of the membranes. PVA/CaAlg/SiO2 membrane exhibited excellent superhydrophilicity (WCA value was 0°) and superoleophobicity underwater (OCA value was 162°). PVA/CaAlg/SiO2 membrane also showed excellent separation performance for water-soluble organic pollutants and can be used for dye separation with rejection efficiencies of 99.5 %, 99.1 %, and 98.3 % for Congo red (CR), Alizarin red (AR), and Sunset yellow (SY), respectively. Moreover, PVA/CaAlg/SiO2 membrane had outstanding long-term filtration and antifouling performance. The biomineralization-inspired structure provides a promising technique that can be used to prepare high-performance organic-inorganic membranes with great promise for wastewater separation application.

Bioinspired EVAL membrane modified with cilia-like structures showing simultaneously enhanced permeability and antifouling properties.

A simple and effective strategy to simultaneously enhance the permeability and antifouling properties of ethylene vinyl alcohol (EVAL) membrane was developed based on the bioinspired natural cleaner, cilia. Taking clue from the self-cleaning effect of cilia, supramolecular polyrotaxanes (PRs) with sliding and rotating cyclic molecules along linear chains were synthesized using azide-alkyne click chemistry. Cilia-like PRs were incorporated into EVAL matrix in the fabrication of modified EVAL membranes. Cilia-like structures protruding from the membrane surface have been observed by SEM, TEM and AFM. By imitating natural ciliary movements, these structures provided a proactive self-cleaning system to remove the foulants. The introduction of cilia-like PRs enhanced the surface roughness and hydrophilicity, and significantly enhanced permeability by 55.3% compared to raw EVAL membrane. Moreover, the membrane modified with cilia-like PRs showed an excellent antifouling property with a lower water flux decline (12.6%) and higher water flux recovery (94%) in dynamic fouling tests. Furthermore, this modified membrane develops the scope of bioinspired membranes, inspiring more attractive potential applications in self-cleaning materials, dynamic membranes and supramolecular machines.