Poly(n-isopropylacrylamide-co-acrylic acid) hydrogel and its thermo-responsive properties for polymer enhanced ultrafiltration

Poly(N-isopropylacrylamide-co-acrylic acid) hydrogel with thermo-responsive properties has been successfully synthesized. The hydrogel functional groups, volume phase transition (VPT) temperature and hydrodynamic size were altered upon copper ion adsorption indicated that the copper ion adsorption had disturbed the hydrogen bonding between the water molecule and the amine/ carboxylic groups present in the hydrogel matrix. It also demonstrates that internal adsorption also play important roles that enhance the copper ion removal. The adsorption process is more favourable at low temperature while the separation process should be carried out at higher temperature to mitigate fouling phenomenon. The hydrophobic behaviour of the hydrogel at temperature higher than the VPT value could minimize its interactions with the hydrophilic membrane.