Cellulose acetate reverse osmosis membranes: Optimization of the composition

Abstract

Membranes based on cellulose acetate for reverse osmosis can possibly be applied to the so-called salinity process of energy generation and water desalinization. The requirements for membranes for these two different applications are a relatively high water flux and low salt permeability. In this article, we present the optimization of the composition of such membranes. We started by producing membranes with a patented casting solution with the following composition: 45.77 wt % dioxane, 17.61 wt % acetone, and 8.45 wt % acetic acid (solvents); 14.09 wt % methanol (nonsolvent); and 7.04 wt % cellulose diacetate and 7.04 wt % cellulose triacetate. The membranes produced with this solution were analyzed comparatively, with the membranes obtained by the introduction of modifications to the following parameters: the solvent mix, the nonsolvent mix, the proportion of cellulose diacetate and cellulose triacetate in the casting solution, and the addition of reinforcing cellulose fibers. The results led us to conclude that the best membrane formulation had the following composition: 45.77 wt % dioxane, 17.61 wt % acetone, and 8.45 wt % acetic acid (solvents); 4.22 wt % cellulose triacetate and 9.86 wt % cellulose diacetate (polymers); 14.09 wt % methanol (nonsolvent); and 0.5 wt % cellulose fibers (with respect to the total polymer content).

Optimization of cellulose acetate nanofiltration membranes for micropollutant removal via genetic algorithms and high throughput experimentation

“…Methanol was selected as non-solvent as the membranes produced with methanol exhibited higher permeabilities and on average relatively higher retentions (for NaCl) compared to membranes prepared with other non-solvents. [20] It is also known that incorporating additives to the casting solution permits obtaining CA membranes with a wide variety of molecular weight cut offs (MWCO) ranging from RO to UF. [22] …”

“…However, the 7 th membrane in the ranking OF (M2-12), has a very good retention (90 %) combined with a reasonable permeability (0.49 Lm -2 h -1 bar -1 ), being comparable to the values for CA-based membranes for reverse osmosis applications. [20] It is important to note that the permeability target in this optimization was too ambitious; therefore high permeabilities were only obtained at the expense of retention.…”

“…Acetone concentration was kept constant at 20 wt% as it is a common solvent for CA and had been fixed in CA membrane formulations in previous work. [20] Dioxane completes the composition up to 100 wt%.…”

Synthesis and characterization of aliphatic polyesters from glycerol, by-product of biodiesel production, and adipic acid

“…The first material derived from biological/ natural sources is cellulose acetate, which is actually a biodegradable thermoplastic with many applications which includes reverse osmosis membranes 1 . The development of the "green" composites based on vegetable fibres (juta, sisal among others) represent a new step into the use of renewable sources for engineering applications 2 .…”

Cellulose acetate reverse osmosis membranes: Optimization of preparation parameters

“…The membranes studied were prepared from a solution whose composition were previously optimized. 4 The authors concluded that the optimum preparation parameters are as follows: thickness of the liquid film of 100 mm; 30 s allowed for evaporation of the solvent; and temperature of coagulation bath of 0-48C and 80-858C as annealing temperature. …”