Aloe vera Rind Valorization to Improve the Swelling Capacity of Commercial Acrylic Hydrogels

Abstract

Acrylic hydrogels have been used in agriculture to increase the availability of water in the soil; cause faster plant growth and increase plant survival to water stress; allow controlled release of fertilizers; and, therefore, increase crop yields. On the other hand, Aloe vera gel production generates a large amount of solid waste as cuticles, which is currently underutilized despite that it is a good source of cellulose nanofibers that could be used to improve the swelling capacity of commercial acrylic hydrogels. In this work, both morphology (SEM) and particle size (TEM) of the cellulose nanofibers obtained from A. vera cuticles by the acid hydrolysis method combined with ultrasound were analyzed; as well as the presence of functional groups (FITR) and thermal stability (TGA). Then, acrylic hydrogels were synthesized by the solution polymerization method, and nanofibers were added to these hydrogels at different concentrations (0% w w−1, 3% w w−1, 5% w w−1, and 10% w w−1). These concentrations had a nonlinear relationship with the swelling capacity, and the hydrogel reinforced at 3% cellulose nanofiber was chosen as the best formulation in this work, as this one improved the swelling capacity of hydrogels at equilibrium (476 g H2O g hydrogel−1) compared to the hydrogel without nanofiber (310 g H2O g hydrogel−1), while hydrogels with 10% nanofiber had a similar swelling capacity to the non-reinforced hydrogel (295 H2O g hydrogel−1). Therefore, cellulose-based superabsorbent hydrogels with potential application in agriculture were developed in this work.