Study of surface modification of recycled ultrafiltration membranes using statistical design of experiments

Abstract

Membrane surface modification on recycled ultrafiltration membrane was conducted using statistical design of experiments by two levels full factorial design. Dip-coting using catechol (CA) and polyethyleneimine (PEI) was chosen as the membrane surface modification method because its simplicity, energy saving characteristics and bio-based character. The factors studied were: CA and PEI concentration (1g/l and 4 g/l), temperature (30ºC and 50ºC) and reaction time (2 and 7 hours). The studied responses were the relative permeability (Pr) and the flux recovery ratio (FRR). A model with good validity was obtained for both responses. Membranes were deeply characterized using several techniques: Scanning electron microscopy (SEM); Attenuated total reflectance–Fourier transform infrared (ATR–FTIR) spectroscopy; X-ray photoelectron spectroscopy (XPS) and Atomic force microscopy (AFM). Statistical design of experiments resulted on a useful tool to understand how the factors affect the surface modification. Surface modification conducted at mild conditions (2 hours; 30 ºC and 1g/l) improved membrane permeability and flux recovery ratio. Moreover, interaction between factors turned out to be significant in the modification process which was an unexplored field in previous works. Modification of recycled membranes is an innovative process that follows a Circular Economy approach.