Acetylated lignin sulfonate as a biodegradable coating for controlled-release urea fertilizer: A novel acetylation method and diffusion coefficient analysis.

Plants require essential nutrients to grow, which soil alone cannot provide. Chemical fertilizers like urea supply the necessary nutrients, including nitrogen. They quickly dissolve in water and can contaminate it with nitrate and nitrite, which can cause diseases. Slow-release fertilizers are a better option to reduce environmental risks. Researchers are exploring cheap and biodegradable alternatives, such as lignin. A critical discussion in the coated urea fertilizer is modeling the nitrogen diffusion process in the coating, which predicts the system's behavior. This article uses lignin sulfonate to coat urea fertilizer, which should first be acetylated with decanoyl chloride. One of the critical parameters is the diffusion coefficient (D). D is determined using the mass transfer flux and the completion time of the effective substance, and with its help, the graph of the total mass transferred from the membrane in a specific time (M) is determined. D equals 6.298813 × 10 cm/s using the time lag method. Also, with the fixed-point convergence method, 5.8849 × 10 cm/s was obtained, which has about 0.80 % error with the D obtained by the time lag method. The M obtained from the analytical method and the experimental data coincides with a minimal error, which indicates high accuracy.