Synergic interactions, kinetic and thermodynamic analyses of date palm seeds and cashew shell waste co-pyrolysis using Coats–Redfern method

Abstract

Date palm and cashew shell wastes are abundant byproducts of the agriculture industry in the UAE, but they are often underutilized and not adequately managed, resulting in environmental problems. For the first time, co-pyrolysis of these wastes was studied to investigate their physicochemical properties, synergistic interaction, thermal degradation behavior, and estimate kinetic and thermodynamic parameters using thermogravimetric analysis with non-isothermal heating rates from 20 to 800 °C and a heating rate of 10 °C/min. The Coats and Redfern method, utilizing twenty-one solid-state reaction mechanisms, was used to perform analyses. The three diffusion models showed the best linear regression with the experimental thermogravimetric data. Co-pyrolysis of cashew shells with date seeds significantly lowered the activation energy (Ea) and produced stable biochar, providing an opportunity to obtain pyrolysis products at better energy efficiency. The estimated Ea for 100% date seeds, 100% cashew shells, and their blend (50:50) were 109, 124, and 113 kJ/mol, respectively. The thermodynamic parameters (ΔH, ΔG, and ΔS) indicated that the pyrolysis process was endothermic but not spontaneous. The novelty of this work lies in investigating the potential of utilizing two underutilized wastes together to produce pyrolysis products. This study is essential for advancing co-pyrolysis of date seeds and cashew shell wastes, optimizing product yields, and understanding their pyrolysis behavior towards experimental pyrolysis.