Tailoring the Morphology and Performance of Polyacrylonitrile Ultrafiltration Membranes for Produced Water Treatment via Solvent Mixture Strategy

The separation performance of membranes is highly dependent on their morphology and microstructure. The present study aims to tailor the characteristics of asymmetric polyacrylonitrile (PAN) ultrafiltration membranes by adopting a solvent mixture strategy, combining dimethylformamide (DMF) and N‐methyl‐2‐pyrrolidone (NMP) for produced water treatment. The ternary phase diagram was used for better analysis of the microstructural changes from the thermodynamics point of view. Using a solvent mixture containing more DMF (i.e., 75 %) and increasing the PAN concentration in the dope were effective in improving the solution viscosity and promoting delayed demixing. As a result, finger‐like macrovoids were suppressed to some extent and the internal morphology of the membranes was transformed into a sponge‐like structure, accompanied by a reduction in the overall membrane porosity and mean pore size. The morphologies and microstructures of ultrafiltration membranes derived from polyacrylonitrile were attuned by new formulations of binary mixed solvents. Improvements were achieved by the simultaneous increase in the polymer concentration in the dope. Optimization of the values of these parameters affected the flux and oil rejection of the membranes, with potential for produced water treatment.