Constrained optimization of cellulose acetate membrane using two‐level factorial design

Abstract

SynopsisThis work preaenta a method, the SUMT algorithm, to optimize the performance of the cellulose acetate (CA) membrane by maximizing the permeate flux subject to an equality constraint of salt rejection and a pair of inequality constrainta for s i h variable.Three variables, i.e., (1) the concentration of fonnamide in the casting solution, (2) the time of evaporation of the membrane prior to gelling, and (3) the annealing temperature of the membrane, were selected for this optimization study. Experiments based on the two-level factorial design were conducted for the determination of regression equations for both premeate flux and salt rejection. At a level of 97.00% rejection of a 0.5% sodium chloride solution at 600 psig, the maximum permeate flux of the CA membrane waa predicted to be 14.52 gallons per day per sq. f t (gfd). This waa later confirmed by experiments. The effects of the casting variables on membrane performance concluded in this study were consistent with those reported by other researchers.

Ranking the key parameters of immersion precipitation process and modeling the resultant membrane structural evolution

“…4 Statistically designed experiments also have been applied to optimize the performance of the cellulose acetate membrane by maximizing the permeate flux at equal salt rejection. 6 Membrane performances were found insensitive to variations in the evaporation time from 2 to 6 s. 6 Evaporation time effect on final membrane performance depends on the initial dope location on phase diagram of the system. 7 Therefore, main membrane characteristics, namely morphology and performance, can be designed by manipulating many effective material and process based parameters.…”

“…Later, it was facilitated by casting a new formulation containing 25 wt % of cellulose acetate, 30 wt % of formamide, and 45 wt % of acetone at room temperature and its direct immersion into nonsolvent. 3 After this finding, several research groups [4][5][6][7] investigated the effects of different effective variables, such as casting solution composition, evaporation time, and coagulation bath temperature on membranes performance prepared from CA-acetone-formamidewater system. The quaternary phase diagram of the system has been determined and used to describe membrane structures and properties.…”