Preparation of MWCNT@ZIF‐L Composites Through In Situ Growth Method and Their Incorporation into CS‐PVA Membrane for Pervaporation Desalination

Abstract In order to prepare high‐performance pervaporation membrane for desalination, multi‐walled carbon nanotube (MWCNT) was introduced into ZIF‐L, and MWCNT@ZIF‐L composite was prepared through in situ growth method. MWCNT@ZIF‐L/chitosan (CS)‐polyvinyl alcohol (PVA) composite membrane was prepared by coating method using MWCNT@ZIF‐L as fillers, CS‐PVA (mass ratio of 8:2) as polymer matrixes and polyacrylonitrile (PAN) membrane as substrate. MWCNT@ZIF‐L composites and MWCNT@ZIF‐L/CS‐PVA membranes were characterized by SEM, FT‐IR, XRD, XPS and water contact angle. MWCNT‐COOH provided the nucleation sites and introduced the hydrophilic groups for the formation of ZIF‐L blade structure. MWCNT@ZIF‐L enhanced the hydrophilicity and anti‐swelling ability for membrane. A small MWCNT amount did not cause obvious change in morphology of ZIF‐L, but a large MWCNT amount was detrimental to the molding of ZIF‐L blade structure. The application of composite membrane in pervaporation desalination was explored. The incorporation of MWCNT@ZIF‐L into polymers brought the more water transport channels and hydrophilic groups, which improved the water flux of membrane without reducing the rejection to salt ions. MWCNT@ZIF‐L/CS‐PVA composite membrane loaded with 1.5 wt% MWCNT@ZIF‐L (1:20) achieved a water flux of 19.8 kg·m −2 ·h −1 and rejection of 99.98%in a NaCl aqueous solution (3.5 wt%) at 35 °C, which was 3.3 times higher than that of CS‐PVA membrane.