A kinetic model of fumigant sorption by grain using batch experimental data

BACKGROUND: Most fumigants are adsorbed by grain at differing rates depending on the fumigant or grain type. Sorption can reduce the concentrations of fumigation doses to sublethal levels before grain has been disinfested. A model to predict fumigant losses due to sorption in industrial scenarios is needed. RESULTS: This work reviews the kinetics of grain fumigant sorption and develops a new alternative model based upon key factors established from the literature and batch experimental results. The novel model accounts for linear mass transfer within the grain, irreversible 'binding' and linear partitioning of the fumigant to the grain. Model coefficients were estimated by minimizing the sum of squared residuals between model predictions and experimental data. The model was compared with other options including diffusion into spheres, and results for methyl bromide and phosphine are provided. CONCLUSION: The model describes the transient changes of fumigant concentrations in both the intergranular air and grain. It provides the capacity to predict fumigant concentrations throughout grain stacks for a wide range of scenarios of industrial importance.