Study on the synergistic effect of clinoptilolite on the swelling kinetic and slow release behavior of maize bran-based superabsorbent nanocomposite

A new type of maize bran (MB)-based superabsorbent nanocomposite with fertilizer slow-release property was synthesized by free-radical graft copolymerization of acrylic acid (AA) and acrylamide (AAm) monomers onto MB backbone in the presence of clinoptilolite (clino) and NPK fertilizer compound. The FTIR results indicated that the grafting reaction and the nanocomposite formation have been performed, successfully. Rheological analyses were done to evaluate the stability of the three-dimensional cross-linked gel network of synthesized hydrogels. The effect of variable factors such as salt solution type and concentration, and solution pH on the water absorbency of hydrogel samples was investigated. Also, swelling kinetic studies for all hydrogel samples were performed. Rheological measurements revealed that all hydrogel samples had a strong gel framework with stable crosslinked network. Moreover, superabsorbent nanocomposite showed higher gel strength compared with neat hydrogel which was due to the additional physical crosslinking effect of clino particles. The equilibrium water absorption capacity of the synthesized hydrogels in all saline solutions was lower than that of values in distilled water. Additionally, hydrogel samples showed pH-sensitive swelling behavior. Fertilizer release studies showed that NPK loaded superabsorbent nanocomposite possesses excellent slow-release behavior. Besides, it had better water retention capacity in soil. These results revealed that the superabsorbent nanocomposite with good slow-release and water retention properties, being cost effective and environment-friendly can efficiently improve the utilization of fertilizer and water resources in agricultural and horticultural applications.