Effect of solvent on the morphology and performance of cellulose triacetate membrane/cellulose nanocrystal nanocomposite pervaporation desalination membranes

Abstract

The effects of different solvents (dimethyl sulfoxide (DMSO), dioxane, 1-methyl-2-pyrrolidinone (NMP), and dimetylformamide (DMF)) on the morphology of nanocomposite membranes intended for pervaporation (PV) and on their desalination performance were investigated. Cellulose triacetate/cellulose nanocrystals (CTA/CNCs) nanocomposite PV membranes were successfully prepared via solution casting in different solvents, aiming to obtain the optimum solvent leading to the best desalination performance. The fabricated nanocomposite membranes were characterized to study the membrane crystallinity, chemical composition, morphology, surface hydrophilicity, mechanical properties, thermal stability and the membrane performance in pervaporation desalination process. DMSO as casting solvent resulted in a transparent PV nanocomposite membrane, while other solvents yielded opaque membranes due to the aggregation of CNCs on the CTA matrix. Among the four solvents, the DMSO-based membranes resulted in a hydrophilic nanocomposite membrane with homogeneously distributed CNCs on the membrane surface and the matrix with self-assembled structure. These membranes showed a high water flux of 11.67 kg m−2 h−1 without compromising NaCl rejection at the level of 99.9% in the feed solution of 30 g L−1 of NaCl. Furthermore, the CTA/CNCs-DMSO nanocomposite membranes also showed a good PV desalination performance for a highly saline feed (up to 90 g L−1 of NaCl) while other membranes suffered from salt penetration and membrane leakage for dioxane-based and NMP-based membranes, respectively. Therefore, DMSO as a green solvent has potential for fabricating CTA/CNCs PV nanocomposite membranes.