Enhancement of separation performance of asymmetric cellulose acetate membrane for produced water treatment using response surface methodology

Produced water is the wastewater generated from the process of exploration in oil and gas production, which needs special treatment. A membrane with cellulose acetate is widely used for produced water treatment, but further developments and improvements are still required. Therefore, it is important to determine the factors of separation efficiency of an ultrathin cellulose acetate membrane by assessing the influence of the composition of the dope solution. The response surface methodology was employed to determine the optimal conditions for this application. The investigations were conducted by varying the cellulose acetate polymer concentration at 18-20 wt.%, polyethylene glycol 4000 at 2-3 wt.% and nonsolvent addition at 3-5 wt.%. The evaluation of membrane performance for the produced water treatment was performed in a dead-end filtration cell with permeate water flux and rejection parameters for turbidity, total dissolved solids, Ca2+, Mg2+ and sulfides of produced water upstream and downstream of the membrane. The optimal composition of the dope solution was: 19 wt.% of cellulose acetate, 3 wt.% of polyethylene glycol, and 5.67 wt.% of non-solvent