Reaction schemes for estimating kinetic parameters of thermal decomposition of native and metal-loaded almond shell

This research aims to provide a better knowledge of the thermal decomposition of almond shell and this material loaded with heavy metals in a previous stage of biosorption (cadmium, copper, chromium, nickel and lead). Firstly, isolation of constituents of the almond shell was carried out. According to chemical analysis almond shell was constituted of an 8.2% of moisture; 1.6% of hot water soluble compounds; 0.34% of ethanol soluble compounds; 50.8% of extract-free lignin; and 49.2% of extract-free holocellulose. Then, experiments were performed by thermogravimetric analysis (TGA) and differential thermogravimetry (DTG) under inert and air atmosphere at a heating rate of 15 K/min for each isolated fraction. After that, adequate reactions schemes were proposed to find kinetic parameters. Independent reactions were formulated for each constituent and kinetic parameters were obtained for each isolated material in a sequential procedure. Finally, the validation of the proposed schemes was verified by the goodness of fitting between experimental and simulated TG and DTG curves. It was observed that cadmium, copper, chromium, nickel and lead present in metal-loaded almond shell did not modify significantly the values of kinetic parameters which describe the thermal decomposition processes. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.