Chitosan-starch superabsorbent polymers for water absorbency in different salts and synthetic urine solutions

Superabsorbent polymers, a three-dimensional cross-linked polymer, show excellent properties in retaining a large amount of water and have been widely applied in various fields. This report studied the synthesis of chitosan-strach superabsorbent by chemical crosslinking. The polymers were prepared by using 1:1 ratio of chitosan and starch in a concentration of 2% w/v with 2-25% v/v of glutaraldehyde as cross-linker. The characterization of chitosan-starch polymers was performed by using analytical tools, such as FTIR and SEM. Water absorption capacity was evaluated by swelling ability followed by the batch sorption of different 0.9% w/v salt solutions of NaCl, MgCl2, FeCl3 and synthetic urine composed of urea, NaCl, KCl, and Na3PO4. The biodegradation was evaluated by the difference mass of polymers before and after plantation in soil. The optimum polymers were obtained by using 5% of glutaraldehyde with water sorption capacity of 349.68%. The water absorbency capacity of different salts was 121.37%, 138.59%, and 165.20% for NaCl, MgCl2, FeCl3, respectively. The absorption capacity of SAP in synthetic urine, 1% w/v NaCl, 0.64% w/v Na3PO4, 0.6% w/v KCl, and 2.43% w/v urea solutions was 87.83%, 117.72%, 103,39%, 99.28%, and 91.08%, respectively. The degradation study indicated that the polymers were completely degraded in 14 days.