Pyrolysis of sulfuric acid-treated chrome-tanned leather wastes: Kinetics, mechanism and evolved gas analysis

[Display omitted] •An acid treatment/pyrolysis combined method was proposed for disposing of CTLS.•Acid treatment affects kinetics and evolved gases of CTLS pyrolysis.•Acid treatment increases the yields of aliphatic hydrocarbons and NH3.•Pyrolysis mechanism can be described by random nucleation and...

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Bibliographic Details
Published in:Waste management (Elmsford) 2022-04, Vol.143, p.105-115
Main Authors: Zhang, Zonghui, Hu, Yadi, Wang, Fang, Zheng, Xuejing, Liu, Jie, Tang, Keyong
Format: Article
Language:English
Subjects:
Chrome-tanned leather wastes
Evolved gases
Gases
Generalized master plots method
Kinetics
Pyrolysis
Sulfuric Acids
Thermogravimetry
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Summary:[Display omitted] •An acid treatment/pyrolysis combined method was proposed for disposing of CTLS.•Acid treatment affects kinetics and evolved gases of CTLS pyrolysis.•Acid treatment increases the yields of aliphatic hydrocarbons and NH3.•Pyrolysis mechanism can be described by random nucleation and nuclei growth model. Management and safe disposal of chrome-tanned leather wastes generated in leather industry are of great importance due to their potential health risks and environmental hazards. Herein, an integrated strategy was proposed for disposing of chrome-tanned leather scrap (CTLS). This method involves the separation of chromium salts from CTLS with sulfuric acid for recycling purpose, followed by pyrolysis of the acid-treated CTLS in an inert atmosphere. SEM/EDX analysis was employed to characterize the changes in composition and morphology of CTLS after acid treatment. CO2 and H2O are main pyrolysis gases of CTLS, while the acid treatment increases the relative content of aliphatic hydrocarbons and NH3 in evolved gases. The pyrolysis characteristics and kinetics of the acid-treated CTLS were investigated by thermogravimetric analysis (TGA) at three different heating rates. After 3 and 6 days of acid treatment, the average activation energy of CTLS (450.9 kJ/mol) obtained from the Flynn-Wall-Ozawa method decreased to 369.6 and 351.0 kJ/mol, respectively. It is assumed that the CTLS consists of two pseudocomponents: low-crosslinked collagen (LCol) and highly-crosslinked collagen (HCol). Using the generalized master plots method, random nucleation and nuclei growth model (An model) was found to be the most probable kinetic model for the pyrolysis process of LCol and HCol. The kinetic exponent for pseudocomponent pyrolysis varied between 3.00 and 3.90, and the pre-exponential factor ranged from 5.83 × 1012 to 2.93 × 1013 min−1. The results of the present study provide an alternative route and useful information for recycling and disposing of chrome-containing leather wastes.
ISSN:0956-053X
1879-2456
DOI:10.1016/j.wasman.2022.02.030