Effects of Operating Conditions on Water Absorption Capacity of Superabsorbent Hydrogels

Abstract

Superabsorbent hydrogels are three-dimensional networks of hydrophilic polymers that have an extraordinary ability to absorb and retain water. Therefore, they have been utilized in many applications such as disposal diapers, drug delivery, and water desalination. In this study, the effects of environmental and synthetic parameters on the absorbency of superabsorbent hydrogels are investigated using a two-level factorial design. Commercial hydrogels were used to examine the effects of temperature, swelling time, pH, and hydrogel amount, whereas synthesized poly acrylamide hydrogels were used to study the effects of monomer, cross-linker, and initiator concentrations. Moreover, both commercial and synthesized hydrogels were characterized using Fourier transform infrared (FTIR) spectroscopy. Higher absorbency is obtained for the commercial hydrogels by increasing the swelling time from two to eight hours. A reduction of 2.8 g/g(g water/g hydrogel) was observed by increasing the level of pH from 8.5 to 10. Water absorption capacity of the hydrogel increased by 14.72 g/g upon increasing the temperature by 8.5oC above room temperature. For the synthesized hydrogel, it was found that increasing monomer concentration by 5% reduces absorbency by 2.51g/g, whereas increasing cross-linkers concentrations from 0.5% to 1.75% decreases the absorbency by 3.01g/g. Increasing the concentration of the initiator by 0.2% was found to improve absorbency by 0.98g/g. The results show that time, temperature, and monomers have positive effects on absorbency while pH, cross-linkers and initiators reduce it.