Deposition of Dopamine and Polyethyleneimine on Polymeric Membranes: Improvement of Performance of Ultrafiltration Process

Abstract

Modification of the characteristics of polymeric membranes is regarded as an alternative to control the flux decline caused by the concentration polarization and the fouling in ultrafiltration (UF). This work investigated the use of dopamine (DA) and polyethyleneimine (PEI) to hydrophilize the surface and to improve the performance of a 50 kDa polyethersulfone UF membrane. The hydraulic permeance of membranes was investigated for the membranes modified using a DA solution with its concentration fixed at 2 mg·mL-1 and a PEI solution with its concentration varying from 0 to 16 mg·mL-1. The membrane modified in a 16 mg·mL-1 solution of PEI presented the uppermost hydraulic permeance (33 L·h-1·m-2). This membrane and two other controls (unmodified and modified membranes with a 2 mg·mL-1 solution of DA) were further characterized for surface chemistry using Fourier transform infrared by attenuated reflectance (FTIR-ATR) and X-ray excited photoelectron spectroscopy (XPS) charge (zeta potential), morphology (field emission scanning electron microscopy (FESEM) and optical interferometry), water mass gain, and performance in bovine serum albumin (BSA) UF. XPS showed an increase in the nitrogen content and a decrease in the sulfur content indicating the membrane modification. Membrane modification with DA/PEI caused an increase in hydrophilicity, which could reduce the interaction of BSA with the membrane surface. The flux of protein solutions was improved by 400%, and there was a complete recovery of the water flux after chemical cleaning of the modified membrane.