Synthesis and performance of polysulfone-chitosan ultrafiltration membranes for humic acid removal

Natural organic matter (NOM) constitutes a significant contaminant in water sources, adversely affecting drinking water quality and complicating purification processes. To mitigate these contaminants, the current state of the application uses membrane filtration along with structural and surface modification of membranes. This study presents the development of polysulfone (PSU) flat-sheet ultrafiltration (UF) membranes, modified with three different concentrations of chitosan (0.05, 0.06, and 0.08 g), a natural polymer, to enhance NOM removal. The membranes were rigorously characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and water contact angle (WCA), porosity, and pore size analysis. Furthermore, the study delves into the interaction mechanisms between chitosan and the PSU polymer matrix, as well as the transport phenomena involved. The findings indicate that increasing the chitosan content from 0.05 to 0.08 g markedly enhanced the membrane's surface properties, reducing the contact angle from 72.8° to 53.5° and nearly doubling the permeation rate despite the decrease in porosity and pore size. The PSU UF membrane with 0.08 g chitosan demonstrated a superior humic acid (HA) rejection rate of 90%, underscoring chitosan's potential for improving polymeric membranes in NOM removal applications.