The Effect of Temperature and Alginate‐Chitosan Composition on the Characteristics of Hydrogel and the Rate of Urea's Absorption

The agricultural sector depends on water resources and fertilizers. Prolonged dry season leads to reduced water availability. Low fertilizer absorption rates cause a decrease in nutrient absorption by plants and result in reduced crop productivity. Therefore, a medium that is able to store water and fertilizer efficiently, is needed. This study was conducted to determine the effect of temperature and alginate‐chitosan composition on the characteristics of hydrogel and the rate of urea absorption. In this study, hydrogels are synthesized from alginate and chitosan with the addition of citric acid as a cross‐linking agent. The characteristics of the hydrogel analyzed in this study are the ratio of swelling and gel fraction. The results show that the process temperature affect the swelling ratio and gel fraction. The resulting swelling ratio ranges from 336.18% to 871.18% and gel fraction are between 66.71% to 91.99%. While the alginate‐chitosan composition has no effect to the swelling ratio and gel fraction. Furthermore, the temperature affects the rate of urea's absorption significantly. The rate of absorption of urea by the hydrogel matrix shows that the most suitable kinetic model of absorption is the Elovich kinetic model.