The Effect of the Pyrolysis Temperature of a Leather-Textile Mixture from Post-Consumer Footwear on the Composition and Structure of Carbonised Materials

Abstract

This paper presents an investigation into the use of pyrolysis to valorise solid waste in the form of post-consumer footwear uppers. A heterogenous leather and textile mixture is studied, produced by crushing some representative samples of post-consumer footwear uppers. The waste has a low ash content and a high net calorific value, which translates into the high gross calorific value of the material. In addition, it contains relatively little S and Cl, which is promising for its use in the process of pyrolysis. The effect of the pyrolysis temperature on the efficiency of carbonising leather and textile mixtures, their physico-chemical parameters, elemental composition, and structure, as well as the development of a specific surface, is investigated. The research results imply that as the pyrolysis temperature grows, the carbonisation efficiency declines. The produced materials consist primarily of C, O, N, and H, whose contents depend on the pyrolysis temperature. Moreover, all the carbonised materials display the presence of two G and D bands, which is typical for carbon materials. Based on the peak intensities of the bands, I_D/I_G coefficients are calculated to assess the organisation of the materials' structures. As the pyrolysis temperature rises, the structural organisation declines, contributing to an increased material porosity and, thus, a greater specific surface of the carbonised materials. This study contributes data on the thermal management and pyrolysis of leather and textile waste into useful carbonised materials. Investigating the applicability of carbonised materials is projected as the next stage of research work.

Keywords: composition and structure of carbonised materials; mixture of leather and textiles; post-consumer footwear; pyrolysis; valorisation of waste.

Figure 1

Leather and textile mixture waste materials: a photo (a) and SEM microphotograph (b).

Figure 2

Carbonised material produced by the pyrolysis of waste leather–textile mixtures: a photo (a) and a SEM microphotograph (b).

Figure 3

The H/C molar ratio in the waste leather–textile mixtures and the resultant carbonised materials.

Figure 4

The FTIR spectra of carbonised materials produced by pyrolysis at varied temperatures.

Figure 5

The Raman spectra of carbonised materials made in the pyrolytic processes of leather–textile mixtures at different temperatures.

Figure 6

N₂ adsorption–desorption isotherms of carbonised materials produced through pyrolysis at varying temperatures: 500 °C (a), 600 °C (b), 700 °C (c), and 800 °C (d).