Generalized Two-Dimensional Perturbation Correlation Infrared Spectroscopy reveals Mechanisms for the Development of Surface Charge and Recalcitrance in Plant-derived Biochars

Journal Article · Wed Sep 05 00:00:00 EDT 2012 · Environmental Science & Technology, 46(19):10641-10650

DOI:https://doi.org/10.1021/es302971d· OSTI ID:1052922

Harvey, Omar R; Herbert, Bruce; Kuo, Li-Jung; Louchouarn, Patrick

Fundamental knowledge of how biochars develop surface-charge and resistance to environmental degradation (or recalcitrance) is crucial to their production for customized applications or, understanding their functions in the environment. Two-dimensional perturbation-based correlation infrared spectroscopy (2D-PCIS) was used to study the biochar formation process in three taxonomically-different plant biomass, under oxygen-limited conditions along a heat-treatment-temperature gradient (HTT; 200-650 oC). Results from 2D-PCIS pointed to the systematic, HTT-induced defragmenting of lignocellulose H-bonding network, and demethylenation/demethylation, oxidation or dehydroxylation/dehydrogenation of lignocellulose fragments as the primary reactions controlling biochar properties along the HTT gradient. The cleavage of OH O-type H-bonds, oxidation of free primary hydroxyls (HTT≤500 oC), and their subsequent dehydrogenation/dehydroxylation (HTT>500 oC) controlled surface charge on the biochars; while the dehydrogenation of methylene groups, which yielded increasingly condensed structures (R-CH2-R →R=CH-R →R=C=R), controlled biochar recalcitrance. Variations in biochar properties across plant biomass type were attributable to taxa-specific transformations. For example, apparent inefficiencies in the cleavage of wood-specific H-bonds, and their subsequent oxidation to carboxyls, lead to lower surface charge in wood biochars (compared to grass biochars). Both non-taxa and taxa-specific transformations highlighted by 2D-PCIS could have significant implications for biochar functioning in fire-impacted or biochar-amended systems.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1052922
• Report Number(s): PNNL-SA-90771
• Journal Information: Environmental Science & Technology, 46(19):10641-10650, Journal Name: Environmental Science & Technology, 46(19):10641-10650
• Country of Publication: United States
• Language: English