Experimental study and modeling of in vitro agrochemicals release from nanoporous anodic alumina

In this study, the ability of nanoporous anodic alumina (NAA) for the controlled release of agrochemicals including indole-3-acetic acid (IAA) and bentazon was investigated. This study was divided into two works. In the first work, the release of IAA loaded into the NAA pores was studied, and a new two-stage mechanism was proposed for the description of this release process. The first stage was modeled using the diffusion-dissolution equation with a moving boundary condition, while the second stage was correlated by the diffusion-dissolution equation with fixed boundary conditions. The proposed model predicts that the release rate in the first stage is first order when the pore diameter is small and is proportional to the reciprocal of the square root of time when the pore diameter is large. The results of the model also demonstrate that in the second stage, the increase in the pore diameter, at first, leads to an enhancement of the release rate; while a further increase in the pore diameter results in a decrease of release rate. In the second work of this study, NAA was used as a barrier membrane to form a reservoir system for the release of bentazon. The experimental data of this study were well fitted to the first-order release model. The results of this model confirm that an increase in the pore diameter leads to an enhancement of the release rate, while an opposite trend was found with increasing the pore length.