Co-pyrolysis behaviour and kinetic of two typical solid wastes in China and characterisation of activated carbon prepared from pyrolytic char

Abstract

This is the first study on the co-pyrolysis of spent substrate of Pleurotus ostreatus and coal tar pitch, and the activated carbon prepared from the pyrolytic char. Thermogravimetry (TG) analysis was carried out taking spent substrate, coal tar pitch and spent substrate–coal tar pitch mixture. The activation energies of pyrolysis reactions were obtained via the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose methods. The kinetic models were determined by the master-plots method. The activated carbons were characterised by N₂-adsorption, Fourier transform infrared spectroscopy and X-ray diffraction. Experimental results demonstrated a synergistic effect happened during co-pyrolysis, which was characterised by a decreased maximum decomposition rate and an enhanced char yield. The average activation energies of the pyrolysis reactions of spent substrate, coal tar pitch and the mixture were 115.94, 72.92 and 94.38 kJ mol⁻¹ for the Flynn–Wall–Ozawa method, and 112.17, 65.62 and 89.91 kJ mol⁻¹ for the Kissinger–Akahira–Sunose method. The reaction model functions were f(α) = (1−α)^3.42, (1−α)^1.72 and (1−α)^3.07 for spent substrate, coal tar pitch and the mixture, respectively. The mixture char-derived activated carbon had a Brunauer–Emmett–Teller surface area up to 1337 m² g⁻¹ and a total pore volume of 0.680 cm³ g⁻¹. Mixing spent substrate with coal tar pitch led to the creation of more micropores and a higher surface area compared with the single spent substrate and coal tar pitch char. Also, the mixture char-derived activated carbon had a higher proportion of aromatic stacking. This study provides a reference for the utilisation of spent substrate and coal tar pitch via co-pyrolysis, and their pyrolytic char as a promising precursor of activated carbon.