Preparation of Oxidized and Grafted Chitosan Superabsorbents for Urea Delivery

Abstract

Different hydrogels based on chitosan were prepared by two environmentally friendly approaches: (i) oxidation under mild conditions and (ii) grafting of itaconic acid. Both procedures guide to it success modification leading hydrogels with adequate crosslinked degree. The hydrogels were structurally and chemically characterized and their swelling behavior was evaluated in water, NaCl and buffer solutions at different pHs. In all the cases, the increase of ionic strength decreases the equilibrium swelling. It was also demonstrated a superior swelling percentage at acidic pH. This percentage of swelling is significantly higher in grafted films than in the oxidized chitosans. Besides, the ability as fertilizers and water controlled-release superabsorbent hydrogels was evaluated. Consequently, the absorption and delivery of urea fertilizer was investigated as a function of initial concentration of urea in the media and the pH. These materials can be used in the agriculture as controlled fertilizer delivery as well as water regulators. Hydrogels based-chitosan were prepared by non-environmentally aggressive approaches. Chitosan was modified by mild oxidation and grafting reaction with itaconic acid. The hydrogels present adequate crosslinked degree and worthy swelling behavior. Hydrogels were evaluated as superabsorbent for urea and water controlled- release.