Novel carbon nanotube-cellulose acetate nanocomposite membranes for water filtration applications

Multi walled carbon nanotube/cellulose acetate (CNT/CA) nanocomposite membranes were successfully prepared by phase inversion using acetone as solvent and 20 wt.% deionized water as non-solvent. CNTs were first functionalized by oxidation purification in a strong acidic medium to enhance their dispersion within the polymer matrix. Small amounts of the functionalized CNTs, namely 0.0005, 0.005, and 0.01 wt.% were used to prepare the membranes. The CNTs were randomly oriented and uniformly dispersed within the membranes. Membranes' morphologies were characterized by field emission scanning electron microscopy (FESEM) and nitrogen adsorption. A decrease in the number of macrovoids with increase in CNT content was observed. This was verified by the analysis of pore sizes (differential volumes and surface areas) which were found to also decrease with the increase in CNT content. Nanocomposite membrane permeation rates and salt retention rates were investigated using a 1000 ppm NaCl solution. Permeation rates were found to improve by 54% with a minimal decrease in salt retention (− 6%) for the membranes with the lowest CNT content. Further addition of CNTs caused a reduction in permeation rates which is attributed to the decreased porosity and surface area.