Development of polyethersulfone and polyacrylonitrile hollow fiber membranes for clarification of surface water and fungal enzyme broth

Abstract

Hollow fiber membranes are of great commercial interest with several applications at the forefront of research to carryout bioseparations, drinking water purification, wastewater treatment besides liquid phase separations and gaseous separations. An experimental study was carried out to synthesize hollow fiber membranes from polyethersulfone (PES) and polyacrylonitrile (PAN) polymers to fabricate modules for surface water treatment and clarification of fungal enzyme broth. Design drawings of a manual hollow fiber spinning machine and spinneret were prepared to fabricate the necessary equipment for extrusion of hollow fibers. Effect of various spinning conditions on specific macroscopic fiber properties, such as outer diameter and wall thickness and membrane pore structure was studied. Concentrations of 15–20 wt% PES in n-methylpyrrolidone (NMP) and PAN in dimethyl formamide (DMF) solvents with important additives and pore formers were prepared. These polymer solutions were extruded through the spinneret and subjected to phase inversion in a water bath. The membranes were characterized by scanning electron microscopy (SEM) and pure water flux studies. PAN and PES exhibited 99.8 and 95.4% turbidity rejection. PAN exhibited a 5 log reduction of Escherichia coli bacteria for surface water treatment at a low hydraulic pressure of 1 bar with a flux of 54.2 L/m2 h at a water recovery of 80% whereas PES gave a flux of 36.6 L/m2 h with 4 log reduction of E. coli. PAN and PES membranes exhibited 54.9 and 69.3% xylanase enzyme recoveries from fungal broth at reasonable flux with turbidity rejection of 94.8 and 95.7% respectively.