Migration studies of lead and cadmium from ceramic food contact materials into acid food simulants were conducted under various time–temperature conditions to investigate the kinetics of the leaching of lead and cadmium. A mathematical model based on one-dimensional Fickian diffusion theory was derived in order to describe the migration behaviour of lead and cadmium. Moreover, diffusion coefficients of toxic metals were obtained by fitting the short-time (24 h) migration data to the model. Comparisons of model solutions with experimental data obtained from the medium-time tests (up to 600 h) and long-time tests (up to 130 days) were carried out to verify the proposed model and the values of diffusion coefficients obtained from the short-time test. Results show that the model fits the experimental data obtained under 20 and 40°C well but fails to fit the experimental data at 60°C. This indicates a change of the migration mechanisms from ion exchange to glass network dissolution as a result of higher temperature. Furthermore, results of migration experiments also reveal that the effects of temperature on the diffusion of lead and cadmium follow the Arrhenius law and that the leaching amounts of lead and cadmium decrease with pH value of the food simulant.
