A1 Journal article (refereed)
Potassium demineralization of coconut fiber via combined hydrothermal treatment and washing : effect on pyrolysis kinetics, mechanisms, and bio-oil composition (2021)

Hungwe, D., Ullah, S., Kilpeläinen, P., Theppitak, S., Ding, L., & Takahashi, F. (2021). Potassium demineralization of coconut fiber via combined hydrothermal treatment and washing : effect on pyrolysis kinetics, mechanisms, and bio-oil composition. Biomass and Bioenergy, 152, Article 106194. https://doi.org/10.1016/j.biombioe.2021.106194

JYU authors or editors

Publication details

All authors or editorsHungwe, Douglas; Ullah, Saleem; Kilpeläinen, Petri; Theppitak, Sarut; Ding, Lu; Takahashi, Fumitake

Journal or seriesBiomass and Bioenergy



Publication year2021


Article number106194

Publication countryNetherlands

Publication languageEnglish


Publication open accessNot open

Publication channel open accessChannel is not openly available


Producing clean energy from waste biomass via pyrolysis is critical in reducing dependence on fossil fuels and alleviating their environmental impacts. Inherent potassium in low energy density coconut fibers reduces bio-oil yield and compromises bio-oil quality and the integrity of reactors within which pyrolysis occurs. The effect of consecutive hydrothermal treatment (180°C-220 °C) and water washing on coconut fiber demineralization, pyrolysis behavior, and bio-oil composition was investigated. Chemical fractionation method classified the most occurring inorganic (potassium) as ~76% water-soluble, ~19% ion-exchangeable, and ~5% acid-soluble species. Demineralization results show that combined pretreatment at ≤200 °C leached out all water-soluble and exchangeable potassium. However, at 220 °C, electrostatic attraction and increased tortuosity imposed by the high density of oxygenated functional groups and a well-developed porous structure hamper demineralization. Nevertheless, a maximum potassium removal efficiency of 95% could be achieved. Although pretreatment marginally affects apparent activation energy, the reaction mechanism of hydrochars became insensitive to the heating rate between 10 and 50 °C min−1. Due to pretreatment, the selectivity of thermally stable phenolic and anhydrosugar derivatives increased at the expense of the light oxygenates of low thermal stability because of suppressing fragmentation reactions and enriching polymers with a high degree of polymerization. Light oxygenates decreased from 27.45 area % to 24.02, 16.33, and 13.32 area % for hydrochars produced at 180 °C, 200 °C, and 220 °C, respectively. Therefore, this pretreatment approach can produce inorganic-free, thermally stable, and chemically stable bio-oils.

Keywordsbiomass (industry)pyrolysis oilfuelsenergy production (process industry)environmental effectsmechanismspotassium

Free keywordsbiomass pyrolysis; hydrothermal treatment; kinetics; mechanism; Py-GC/MS

Contributing organizations

Ministry reportingYes

Reporting Year2021

JUFO rating2

Last updated on 2024-03-04 at 19:55