Insights into the co-pyrolysis of olive stone, waste polyvinyl chloride and Spirulina microalgae blends through thermogravimetric analysis

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Co-pyrolysis of binary and ternary blends composed of different biomass samples was analyzed based on thermogravimetric analysis (TGA). The study was carried out considering biomass samples from very different origins and uses, including Olive Stone (OS) as a representative of lignocellulosic biomass, waste Polyvinyl Chloride (PVC) as an example of a widely generated residue, and Spirulina microalgae (MA) as an archetype of a highly valuable biomass. The synergetic effects of mixing and combining these dissimilar biomass samples were evaluated. The obtained results were evaluated by four iso-conversional methods, namely Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), Starink (STK), and Modified-Friedman (M-F) to determine the activation energy and the pre-exponential factor of the process, whereas the order of reaction was calculated by Coats-Redfern model. By analyzing the correlation coefficient, the FWO model was found to better describe the thermogravimetric results for single, binary and ternary blends. The lowest and highest values of calculated activation energy correspond to OS and MA samples, obtaining values of 80.8 kJ/mol and 158.7 kJ/mol, respectively. Additionally, blending of OS, MA and PVC with a composition of 50%:25%:25% resulted in lower activation energy for ternary mixtures. The synergistic and inhibitive effects of the addition of the second and third components were also investigated according to the comparison of the experimental and theoretical mass evolutions. The results confirmed the existence of synergistic effect for the interaction between PVC-OS in the complete temperature range during the process, while the synergistic interaction between MA-OS and PVC-MA were observed above conversion values of 0.15 and 0.8, respectively. Furthermore, for all mass ratios of ternary blends, the interaction effect was inhibitive for low temperatures and then turned into synergistic for increasing temperatures.
Co-pyrolysis, Biomass, Microalgae, Thermogravimetric analysis, Kinetic parameters
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Algal Research, (2022), v. 62, 102635.