Kinetic model of the thermal pyrolysis of chrome tanned leather treated with NaOH under different conditions using thermogravimetric analysis

- Thermogravimetric analysis of chrome tanned leather.
- Kinetic study of untreated and treated with NaOH chrome tanned leather.
- Kinetic model based on three independent reactions and a consecutive one.
- Multi-reaction processes imply complex fitting models.

The thermal decomposition of chrome tanned leather before and after a soaking treatment with NaOH was studied using thermogravimetric analysis (TGA). The effect of the solution concentration (0.2 M and 0.5 M) and the soaking time (5 min and 15 min) was evaluated. TGA experiments at four heating rates (5, 10, 15 and 20 °C min−1) were run in a nitrogen atmosphere for every treatment condition. A kinetic model was developed considering the effect of the three variables studied, i.e.: the NaOH solution concentration, the soaking time and the heating rate. The proposed model for chrome tanned leather pyrolysis involves a set of four reactions, i.e.: three independent nth order reactions, yielding the corresponding products and one of them undergoing a successive cero order reaction. The model was successfully applied simultaneously to all the experimental data obtained. The evaluation of the kinetic parameters obtained (activation energy, pre-exponential factor and reaction order) allowed a better understanding of the effect of the alkali treatment on these wastes.