Modification and Characterization of Polyethersulfone (PES) Membranes — 10a — Basmala Alemam

Natural Organic Matter (NOM), which has chemical properties that allow it to bind to fluoride, pharmaceuticals, and pesticides, is present in abundance in Earth’s natural systems. However, it creates other disinfection byproducts in drinking water and clogs and fouls water filtration membranes due to its tendency to self-aggregate. NOM in any soil type can be fractionated into distinct fractions, including an amphiphilic fraction that has a narrowed range of solubility and can be covalently bonded to polyethersulfone (PES) membranes. This study explores the possibility of the amphiphilic fraction’s ability to resist fouling as a result of decreased hydrophobicity of the membrane surface, and to investigate whether more neutral chemicals can be used for membrane cleaning narrows due to the fraction’s limited solubility. 

PES membranes were modified via a UV-induced photoreaction with the amphiphilic humic fraction of Leonardite and Pahokee Peat bulk soil types (identified as LHA₂ and PHA₂, respectively). Additionally, to test an environmentally sustainable method for cleaning membranes used in filtration, membranes were washed with strong acids and bases (pH 2 and 11) then compared to membranes washed under less harsh conditions (pH 5 and 9). 

LHA₂– and PHA₂-modified membranes were characterized and compared with unmodified membranes via ATR-FTIR, SEM, zeta potential, and contact angle measurements. Cross-flow filtration has been used to test the control, LHA₂-, and PHA₂-modified membranes for water filtering capacity and cleaning efficiency. Fluorescence spectroscopy has also been performed to determine NOM concentrations before and after filtration of water samples. 

Preliminary results of the modified membranes have shown a decrease in contact angle and an increase in the ATR-FTIR carboxylic acid stretch, which correlates to an increase in hydrophilicity. Additionally, the surface zeta potentials of modified membranes in solutions of NOM (8 mgC/L in 5 mM NaCl) show a decreased magnitude compared to unmodified membranes.

Augustana University
Dr. Cyndey Johnson-Edler