pH-Responsive Nanofiltration Membranes for Sugar Separations

Nanofiltration membranes were surface modified by grafting polyacrylic acid nano-chains using UV initiated free radical polymerization method.  These pH-sensitive membranes were then used to separate monosaccharide, disaccharide and their mixtures from filtration feed streams. It was found that pH dramatically affects the flux, rejection and selectivity using these modified pH sensitive nanofiltration membranes.  Classical molecular dynamics simulations were conducted to investigate the effects of pH on sugar separations. We found that membrane performance could be enhanced not only by the conformational changes of the grafted surface layer due to protonation and deprotonation of the acid groups on the polymer chains, but also from the different interactions between the sugar molecules and the neutral polyacrylic acid chain or its negative conjugate.