Mathematical modeling of controlled-release kinetics of herbicides in a dynamic-water-bath system

Release of herbicides from lignin-hased formulations follows a diffusion-co ntrolled mechanism. For mathematical modeling of diffusive transport, the c onventional approach is to assume sink conditions at both surfaces of polym eric matrix. This boundary condition proved to be inadequate to describe ex perimental data obtained in a water dynamic bath system. However, satisfact ory descriptions for this system were obtained when a stagnant unstirred la yer of herbicide solution was used as the boundary condition. The adequacy of the model incorporating this new boundary condition was statistically te sted using the Fisher test at a confidence level of 95% and plotting the re sidual distribution.