Superabsorbent hydrogel from cassava gum (Manihot esculenta) to release water and macronutrients

The application and development of biopolymers as water storage and macronutrient release systems are attractive due to their biocompatibility and high bioavailability in the environment. Cassava gum is a polysaccharide obtained from Manihot esculenta tubers, consisting of 80–86 % starch, with an excellent ability to form a hydrogel. The objective of this research was the synthesis of hydrogels from the copolymerization of cassava gum and polyacrylamide. The material was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry, a scanning electron microscope, and porosity to understand the formation of the new hydrogel better. The hydrogel was studied for its swelling capacity at different pH levels, its controlled release of macronutrients, and its toxicity test against Artemia saline. The swelling study shows that the hydrogels have better water absorption in more neutral media with expansion capacity (∼ 270 folds). Phosphate release began 30 min after contact with the medium and remained constant after 24 h in solution, with the hydrogels not demonstrating toxicity. Hydrogels formed satisfactorily with and without phosphate incorporated into the polymeric matrix, thus resulting in a superabsorbent and promising material for the controlled release of macronutrients. [Display omitted] •New hydrogels have been innovatively synthesized from cassava gum.•Hydrogels exhibit high water storage capacity and were classified as superabsorbent.•The hydrogels did not present toxicity and exhibited good porosity.•The hydrogel was used as a fertilizer carrier and showed promise in agriculture.