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.