High-performance separation for ultra-low concentration nanoparticles with mesoporous silica thin membrane

Mesoporous silica thin film membrane (MSTF) emerges as an ideal ultrafiltration membrane for the removal of nanoparticles, ensuring the production of particle-free water. This is mainly ascribed to its uniform and narrow pore size distribution, having vertical nanochannels with low tortuosity, and being ultrathin, which helps enhance its selectivity and permeability. In this study, we demonstrated the potential of MSTF overlayed on macroporous anodic aluminum oxide (AAO) support for separating gold nanoparticles even at a very low concentration. Moreover, with the addition of pore-expanding agents, E-MSTF⊥AAO (pore size 3.12 nm) and D-MSTF⊥AAO (pore size 5.26 nm) membranes are formed, and both membranes indeed showed high rejection efficiency towards 150 ppb gold nanoparticles of sizes 10 nm and 5 nm, ∼99 %, and ∼96 %, respectively. It is also worth noting that as compared to the state-of-the-art conventional UF membranes, the E-MSTF⊥AAO membrane showed significantly high permeance of 114.1 ± 12.76 L m⁻² h⁻¹ bar⁻¹ and 104.1 ± 50.6 L m⁻² h⁻¹ bar⁻¹ while efficiently separating 150 ppb and 50 ppb 5 nm gold nanoparticles, respectively. Moreover, the promising long-term stability and chemical stability of the MSTF⊥AAO membrane paved a promising path for applying mesoporous silica membranes for effective nanoparticle separation in wastewater treatment and particle-free water production in industries.