Radiation synthesis of superabsorbent hydrogels based on Carbopol 940 for fast swelling and slow release of urea fertilizer

Abstract In this study, a superabsorbent hydrogel based on Carbopol 940, carboxymethyl cellulose sodium salt (NaCMC), and acrylic acid (C/NaCMC/PAc) was prepared using gamma radiation. This technique serves as a clean and effective method for initiation and crosslinking, intended for agricultural use as a slow-release urea fertilizer. The parameters affecting the gelation percentage, such as Ac and Carbopol contents, as well as different irradiation doses, were studied. The optimal conditions for preparing C/NaCMC/PAc hydrogel were achieved with acrylic acid and Carbopol concentrations of 5 wt% and 3 wt%, respectively, at an irradiation dose of 5 kGy. The swelling rate was enhanced by increasing the Carbopole content, while its degree was enhanced by treating the prepared hydrogel with di-ethanolamine and raising the pH, reaching a swelling degree to 78 g/g. FTIR, XRD, EDX, and SEM were performed to characterize the structure and properties of the fabricated hydrogels. The synthesized hydrogels exhibited excellent urea loading (92 %) and slow release (91 % after 16 days). The extended urea release of Carbopol-co-poly-Ac hydrogels makes them a potential candidate for controlled delivery of urea fertilizer. The data showed that the prepared superabsorbent hydrogel has some advantages and can be used as a slow-release urea fertilizer.