Air nanobubbles (ANBs) incorporated sandwich-structured carbon nanotube membranes (CNM) for highly permeable and stable forward osmosis
Lu Zhang, Fu Liu, Simin Yang, Shenghua Zhou, Jian‐Qiang Wang, Haibo Lin, Qiu Han, Chuyang Y. Tang
Abstract
The selective transport of water/ions through conventional forward osmosis (FO) membranes is largely impeded by solution-diffusion and internal concentration polarization (ICP). Herein, we report a novel air nanobubbles (ANBs) incorporated sandwich-structured carbon nanotube membrane (CNM) for highly permeable and stable FO desalination by taking advantage of the nanofluidic transport at the solid/liquid/vapor interface. Fluorinated multi-walled carbon nanotubes (F-MWCNTs) were assembled as the superhydrophobic interlayer between a hydrophilic cellulose acetate (CA) layer and a hydrophilic polyacrylonitrile (PAN) nanofibrous layer. The trapped ANBs in the superhydrophobic F-MWCNT layer crucially regulated the continuous water flow and effectively prevented salt diffusion. When tested with DI water as feed solution (FS) and 1 M NaCl as draw solution (DS), the ANBs incorporated sandwich-structured CNM achieved high water flux (158.0 L m−2 h−1) and ultralow reverse salt flux (0.4 g m−2 h−1) simultaneously, far beyond the state-of-the-art FO membranes. The PAN nanofibrous layer well protected the entrapped ANBs to allow a more durable FO performance. An ANBs-regulated nanofluidic flow model was proposed to elucidate selective water/salt transport mechanism. This work revealed the feasibility of ANBs incorporated membranes for osmosis-driven processes.