Brine desalination via pervaporation using kaolin-intercalated hydrolyzed polyacrylonitrile membranes

Abstract

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 wellorganized, 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 m2h-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 degrees C feed temperature.