Impact of sodium hypochlorite (NaClO) on polysulfone (PSF) ultrafiltration membranes: The evolution of membrane performance and fouling behavior

This paper presents a study on the impact of sodium hypochlorite (NaClO) on the performance and fouling behavior of polysulfone (PSF) membranes. The performance of aged PSF membranes was studied under different transmembrane pressures (TMPs), and three critical TMPs including the pressure corresponding to critical flux (PC), the pressure corresponding to critical filtration efficiency (PV), and the pressure corresponding to the greatest retention ability (PR) were innovatively proposed. In terms of an aged membrane, the filtration efficiency (ηv) and retention ability (R) were decreased, while, the enhanced sieving capacity (ηs) were experimentally proved. These are strongly related to modified surface properties and enlarged pore diameters of aged PSF membranes. The fitting results of Hermia's model and critical flux analysis mutually verified that the formation of cake layer fouling on an aged PSF membrane surface was delayed. However, the specific fouling results indicated the aged membrane suffered a more severe pore block fouling. Moreover, the target plot also implied that the critical parameters (PC, PV and PR) can serve as indicators of the evolution of membrane performance and fouling behaviors.