Water transport behavior of chitosan porous membranes containing multi-walled carbon nanotubes (MWNTs)

In this work, the effects of MWNTs content on water transport behaviors and tensile properties of prepared chitosan porous membranes were investigated. In the case of chitosan membrane using low molecular weight PEG6000 as a porogen, a percolation-like behavior of water transport rate was observed for the first time in composite membranes with a critical MWNTs content (5 wt%). The water flux of composite membrane with 10 wt% MWNTs (128.1 L/m2 h) is 4.6 times that of neat one (27.6 L/m2 h). This could be understood as due to the formation of MWNTs network located among the pore network of chitosan membrane at high MWNTs content, where the hollow nanochannel of MWNTs and their interspaces could provide a new transport channel for water. In contrary, when high molecular weight PEG10000 is used as the porogen, a decreased water flux of the prepared composite membrane is found with increase of MWNTs content. In this case, a strong compatibilizing effect of MWNTs on chitosan/PEG10000 blends is observed, resulting in a decreased pore size and poor water flux of the membranes. Furthermore, a greatly improved tensile strength of chitosan porous membranes has been achieved by adding MWNTs, no matter which molecular weight PEG is used as porogen. Our work provides a novel way to improve water flux and/or control the pore size of polymer porous membranes by using MWNTs.