Spray-dried chitosan/nanocellulose microparticles: synergistic effects for the sustained release of NPK fertilizer

Enhanced efficiency fertilizers help to provide desirable nutrients to plants and release them in a prolonged time. The public concern about environmental protection and efficiency in the use of resources has increased the need to produce eco-friendly and high-performance products. In this work, we report the preparation and properties of the sustained release of spray-dried microparticles based on two biopolymers, chitosan, and nanocellulose. Cellulose rich solid was isolated from waste sugarcane bagasse by chlorine-free alkali peroxide procedure, yielding solids at 45.2%. Nanocellulose with sulfate groups attached on its surface was obtained by acid hydrolysis, and then it was incorporated into chitosan (CS) and NPK fertilizer solution, followed by spray drying to yield microparticles. The CS microparticles caused a decrease in the initial release rate of NPK, which resulted in extended-release of the entrapped nutrients (around 2 h). The incorporation of 10 wt.% nanocellulose to microparticles provided the most significant reduction on fertilizer release rate within 5 h. The work demonstrates the potential use of sulfated nanocellulose in biopolymeric matrices to design enhanced fertilizer release systems.