Effect of Salinity on Swelling Behaviors of Superwater Absorbent Hydrogel Prepared from Carboxymethyl cellulose/Acrylamide Blends by Gamma Radiation

Abstract

Polysaccharide-based hydrogels act like smart materials and exhibit a wide range of properties that can be utilized for several applications. Polysaccharide-based super water absorbent (SWA) hydrogel was prepared from an aqueous solution of carboxymethylcellulose (CMC)/acrylamide (AAm) Using gamma radiation from a Co-60 gamma source at room temperature (~27°C). Functional groups of the prepared hydrogel were characterized in terms of Fourier Transform Infrared Spectroscopy-Attenuated Total Reflectance (FTIR-ATR). The swelling of the SWA in water and the saline solutions (NaCl, CaCl2, and AlCl3) was examined. It was found that the swelling value of the SWA in water is higher (27900%) than those of in the saline solutions (2074% in NaCl, 1718% in CaCl2 and 796% in AlCl3). Results also indicated that the swelling capacity of SWA in saline solution decreases with an increased charge of cation in salt. Swelling ratio in NaCl solution was the highest which was 26, followed by 12.48 in CaCl2 and 6.22 in AlCl3 solution. A comparative swelling study was done by changing the cationic size of the same group elements (between KCl and NaCl). This study suggested that the swelling of the SWA depends upon the cationic size. Compared to the swelling of 2074% in NaCl solution, the swelling in KCl was found to be slightly higher (2442%). This behavior can be attributed to the charge screening effect for monovalent cations, as well as the ionic crosslinking of the SWA with the multivalent cations.