Chlorine-resistance, reswelling after drying and molecule/ions separation properties of carboxyl multi-walled carbon nanotubes/calcium alginate composite hydrogel membrane

In practice sodium hypochlorite (NaClO) is often used to clean biological contamination from membrane surfaces. It is worth thinking about how to balance the mechanical strength and chlorine resistance of calcium alginate (CaAlg) hydrogel membrane during cleaning. In this study, carboxyl multi-walled carbon nanotubes/calcium alginate (CMWCNT/CaAlg) composite hydrogel membrane with chlorine-resistance ability was prepared. Performance of CMWCNT/CaAlg membrane in various aspects, including morphology and chlorine resistance, were characterized. In addition, vacuum drying and reswelling method enhanced the mechanical strength of the membrane. Moreover, the interactions mechanism between CMWCNT and NaAlg were investigated by isothermal titration calorimetry (ITC) and molecular dynamics (MD) simulation. Subsequently, the factors influencing membrane separation efficiency towards dye molecule/salt ions were analyzed. It turns out that the composite membrane could achieve nearly 100% high efficiency in the rejection of dye molecules with large molecular weight (Mw > 700 Da), while the rejection of salt was below 8%. Our findings demonstrated CMWCNT/CaAlg composite membrane not only has excellent anti-fouling and chlorine resistance, but also has a very broad application prospect in the separation of dye and salt.