Brine desalination via pervaporation using kaolin-intercalated hydrolyzed polyacrylonitrile membranes

Polyacrylonitrile (PAN) has been mostly used as a base polymer for asymmetric membrane synthesis with the aim of pervaporation (PV) applications, since it has a superior hydrophilicity and the ability to become hydrolyzed with an alkaline solution. Nonetheless, PAN and hydrolyzed PAN membranes have shown moderate permeate fluxes along with a mechanical softness. In this study, we aimed to improve the PV performance by exploring the possible effect of the hydrolysis of a novel mixed matrix membrane based on PAN and kaolin. Specifically, 15% PAN was used as a dope solution along with varying concentrations (2, 5, 7, and 10%) of kaolin to synthesize mixed matrix membranes using a non-solvent-induced phase separation technique. The 2% kaolin addition maximized the hydrophilicity and water sorption capacity of the membrane by developing well-organized, deep channel structures with increased porosity, membrane thickness, and surface roughness. The tensile strength was also the highest with the 2% kaolin addition. Further hydrolysis of the 2% kaolin-embedded PAN caused an extra enhancement of its hydrophilicity with a decrease of pore size due to the amplified carboxylic group density. PV performance tests under different salt concentrations confirmed that the hydrolyzed PAN membrane with a 2% kaolin intercalation had an outstanding permeation flux of 82 kg m^-2h⁻¹ and 59 kg m^-2h⁻¹ as well as a salt rejection of 99.93% and 99.91% with a 3.5% and 10% NaCl solution, respectively, at a 65 °C feed temperature.