Phosphonic acid containing superporous hydrogels and their adsorption properties

In this study, poly[(1-vinyl 1,2,4-triazole)-co-(vinylphosphonic acid)] (poly(VTAz/VPA)) hydrogels were prepared by ⁶⁰Co γ-irradiation of binary mixtures of 1-vinyl 1,2,4-triazole and vinylphosphonic acid in the presence of NaHCO₃. In binary systems, the percentage gelation decreased with increasing phosphonic acid content. For the hydrogels with a high phosphonic acid content, gelation of 75% was reached at around 25 kGy dose at the end of irradiation. The structural changes were followed by using FTIR/ATR spectroscopy. Mercury intrusion porosimetry and SEM methods were used to analyze pore structure of poly(VTAz/VPA) hydrogels. The effects of time, pH, temperature, and ionic strength on the swelling behavior were investigated. Swelling equilibrium was attained within 2 days. Rapid increase in swelling was observed at basic pH region. An increase in swelling was observed as the temperature increases. The swelling ratios of the gels decreased with increasing ionic strength. Poly(VTAz/VPA) hydrogels were tested two different area to show usability for separation purposes: One is radioactive heavy metal ion adsorption and the other is water removal from biofuels. As a result, poly(VTAz/VPA) hydrogels showed stimuli-responsive properties depending on surrounding medium; therefore, they are being considered for adoption as some kind of carrying material for separation purposes.