Superabsorbent hydrogel based on sulfonated-starch for improving water and saline absorbency

Abstract The agriculture sectors in many developing countries have been suffering from water shortage and decreasing crop yields. Thus, an increasing interest has been emerged to develop much-needed solutions for a more sustainable management of water resources. Agricultural hydrogel that absorbs many times of its weight in water has been used to distribute into dry regions in order to improve the soil's ability to absorb and retain water. Here, amphoteric superabsorbent hydrogel is prepared by indirect method based on anionic starch bearing sulfonate groups. Anionic starch derivatives were graft-polymerized with acrylonitrile (AN) and hydrolyzed by alkaline by which nitrile groups were converted to hydrophilic functional groups. The hydrolyzed sodium starch sulfate- g -polyacrylonitrile (HSSS-g-PAN) copolymer exhibited improved water and saline absorbencies compared to that of native starch-based hydrogel. The co-polymerization was conducted for 60 min polymerization time, 0.75% (wt/wt) ammonium persulfate (APS) associated with sodium bisulfite, SBS, (50% (wt/wt) of APS), 65 °C for polymerization temperature and double molar ratio of acrylonitrile to the starch derivatives. The hydrogel based on the sulfonated starch derivatives 1 and 2 showed superior water absorbency for both distilled (250% and 190% respectively) and saline (90% and 70%) solutions over that of the native starch.