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Thermogravimetric Analysis and Pyrolysis Kinetics of Tannery Wastes in an Inert Atmosphere

Industrial wastes generated from tanneries contain large quantities of water-insoluble proteins, which may be used for the production of composite materials, renewable chemicals and energy. In this work, the pyrolysis kinetics of powdered sheep fur wastes (SFW) was studied by thermogravimetry (TG) at different heating rates from room temperature to 600°C in nitrogen atmosphere. TG results revealed that there are three stages in this process. The overall apparent activation energy (E) in the main pyrolysis stage was determined to be 275.6 kJ mol-1 by modified Kissinger-Akahira-Sunose (MKAS) method. Because the pyrolysis of SFW could not be described by a single-step reaction, the experimental DTG curve of SFW was deconvoluted into three individual peaks followed by reconstruction of TG curves corresponding to three pseudo components. The average values of E obtained for these pseudo components are 234.7 kJ mol-1, 176.4 kJ mol-1, and 186.2 kJ mol-1, respectively. Generalized master-plots method indicated that the SFW pyrolysis may follow the random nucleation and growth mechanism (Avrami-Erofeev model). Reaction model functions f(α) for these pseudo components could be expressed as: f(α)=3.1(1-α)[-ln(1-α)]0.67; f(α)=3.6(1-α)[-ln(1-α)]0.72, and  f(α)=3.9(1-α)[-ln(1-α)]0.74, respectively. These results may provide insight for further studies as well as for future application of pyrolysis technology for tannery wastes.