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Open AccessArticle

Ferrous and Ferric Ion-Facilitated Dilute Acid Pretreatment of Lignocellulosic Biomass under Anaerobic or Aerobic Conditions: Observations of Fe Valence Interchange and the Role of Fenton Reaction

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Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401, USA
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National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO 80401, USA
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Authors to whom correspondence should be addressed.
Academic Editors: Jalel Labidi and Xabier Erdocia
Molecules 2020, 25(6), 1427; https://doi.org/10.3390/molecules25061427
Received: 25 February 2020 / Revised: 17 March 2020 / Accepted: 18 March 2020 / Published: 20 March 2020
(This article belongs to the Special Issue Biorefineries)
Ferrous ion co-catalyst enhancement of dilute-acid (DA) pretreatment of biomass is a promising technology for increasing the release of sugars from recalcitrant lignocellulosic biomass. However, due to the reductive status of ferrous ion and its susceptibility to oxidation with exposure to atmosphere, its effective application presumably requires anaerobic aqueous conditions created by nitrogen gas-purging, which adds extra costs. The objective of this study was to assess the effectiveness of oxidative iron ion, (i.e., ferric ion) as a co-catalyst in DA pretreatment of biomass, using an anaerobic chamber to strictly control exposure to oxygen during setup and post-pretreatment analyses. Remarkably, the ferric ions were found to be as efficient as ferrous ions in enhancing sugar release during DA pretreatment of biomass, which may be attributed to the observation that a major portion of the initial ferric ions were converted to ferrous during pretreatment. Furthermore, the detection of hydrogen peroxide in the liquors after DA/Fe ion pretreatment suggests that Fenton reaction chemistry was likely involved in DA/Fe ion pretreatments of biomass, contributing to the observed ferric and ferrous interchanges during pretreatment. These results help define the extent and specification requirements for applying iron ions as co-catalysts in DA pretreatments of biomass. View Full-Text
Keywords: dilute acid pretreatment; metal co-catalyst; ferric ions; ferrous ions; biomass; cellulose; corn stover; hydrogen peroxide; Fenton reaction dilute acid pretreatment; metal co-catalyst; ferric ions; ferrous ions; biomass; cellulose; corn stover; hydrogen peroxide; Fenton reaction
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Wei, H.; Wang, W.; Ciesielski, P.N.; Donohoe, B.S.; Zhang, M.; Himmel, M.E.; Chen, X.; Tucker, M.P. Ferrous and Ferric Ion-Facilitated Dilute Acid Pretreatment of Lignocellulosic Biomass under Anaerobic or Aerobic Conditions: Observations of Fe Valence Interchange and the Role of Fenton Reaction. Molecules 2020, 25, 1427.

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