INTERPRETATION OF STRUCTURE AND ELECTRICAL PROPERTIES OF A POLYAMIDE NANOFILTRATION MEMBRANE

Nanofiltration has made tremendous progress during the past decades due to its excellent removal of contaminant from wastewater. These membranes have gained interest recently for the treatment of inorganic effluent to reduce the amount of wastewater produced and in addition improve the quality of effluent. The basic principle of nanofiltation separation is by sieving effect and electrical charge of a membrane. This can be clearly understood by determining the structural (pore radius and membrane porosity ratio) and electrical properties of a membrane. A polyamide thin composite NF membrane (AFC 30) was used to characterize the structural and electrical parameters. The structural values were estimated with permeation experiments of aqueous solution of neutral solutes in conjunction with steric hindrance model (SHP). The fixed charge density on the membrane surface was determined using sodium chloride experiments at different concentrations. The data from sodium chloride experiment were used to evaluate the effective charge density (Phi X) by using the Spiegler-Kedem model together with the charge model called Teorell-Meyer-Sievers (TMS). It was found that the membrane charge depends solely on the salt concentration in the solution, which is because of ion adsorption on the membrane surface.