Dehydration of isopropanol–water mixtures using a novel cellulose membrane prepared from cellulose/N-methylmorpholine-N-oxide/H 2O solution

Abstract

A novel cellulose membrane used for isopropanol (IPA) dehydration was prepared by using N-methylmorpholine-N-oxide monohydrate (NMMO·H 2O) as the solvent that can dissolve cellulose through a purely physical process. Scanning electron microscopy (SEM) images show that the prepared membrane had a homogeneously dense structure after natural drying. X-ray diffraction (XRD) and mechanical properties characterizations show that the prepared cellulose membrane owned much higher crystallization degree and better mechanical strength compared with traditional cellulose acetate (CA) or cellophane membranes coming from chemical process. The effects of operation conditions including feed concentration and operation temperature on pervaporation (PV) performance were investigated systemically. The results indicate that the permeation flux increased obviously with the increase of either water concentration in feed or operation temperature. Under the condition of 20 wt.% water-containing IPA feed and at 65 °C, a highest total flux of 349 g/m 2 h was achieved with a lowest water content in permeate of 99.50 wt.% (with a separation factor of 972) among all the tested conditions. Water content in permeate reached 99.97 wt.% (with a separation factor of 61,271) with a total flux of 13.4 g/m 2 h at the condition of 5 wt.% water in feed at 25 °C. Compared with other pure polymer membranes such as chitosan and poly(vinyl alcohol) (PVA), the prepared novel cellulose membranes exhibited acceptable fluxes and much higher separation factors. All these results demonstrate that cellulose membrane has great application potential in IPA dehydration process.