Charge and Size-Selective Molecular Separation using Ultrathin Cellulose Membranes
15:00 - 15:30
Level 0, between bld. 4 and 5
To date, it is still a challenge to prepare high-flux and high-selectivity microporous membranes thinner than 20 nm without introducing defects. Cellulose has emerged as an important membrane material due to its price, availability, compatibility, antifouling feature, chemical and mechanical stability. However, the intensive hydrogen bonds within its closely packed structure makes this polymer insoluble in most organic solvents. Conventional cellulose membranes are predominantly prepared using selected solvents, which often suffer from high reactivity and toxicity. One effective strategy to avoid the cumbersome solvents is the use of functionalized soluble cellulose, which is regenerated back to cellulose after membrane formation. In this work, we prepared ultrathin cellulose membrane using trimethylsilyl cellulose (TMSC) as a precursor. The elegance of this method lies on the in situ transformation of TMSC back to cellulose, which is reproducible, relatively simple and can be mass-produced. More interestingly, a freestanding cellulose membrane as thin as 10 nm is capable of precisely sieving anionic over neutral molecules on the basis of size and charge differences, providing an estimated pore size between 1.5 – 3.5 nm depending on the regeneration period and initial TMSC concentration. The membrane can be transferred to any desired substrate and shows a normalized flux as high as 700 Lm-2h-1bar-1 when supported by a porous alumina disc. Furthermore, the membrane demonstrates high reproducibility, high scale-up potential and excellent stability over two months. This is one of the best separation performances ever demonstrated by cellulose membranes.