Aged Lignocellulose Fibers of Cedar Wood (9th and 12th Century): Structural Investigation Using FTIR-Deconvolution Spectroscopy, X-Ray Diffraction (XRD), Crystallinity Indices, and Morphological SEM Analyses

Abstract

The characterization of lignocellulosic biomass present in archaeological wood is crucial for understanding the degradation processes affecting wooden artifacts. The lignocellulosic fractions in both the external and internal parts of Moroccan archaeological cedar wood (9th, 12th, and 21st centuries) were characterized using infrared spectroscopy (FTIR-ATR deconvolution mode), X-ray diffraction (XRD), and SEM analysis. The XRD demonstrates a significant reduction in the crystallinity index of cellulose from recent to aging samples. This finding is corroborated by the FTIR analysis, which shows a significant reduction in the area profiles of the C-H crystalline cellulosic bands (1374, 1315, and 1265 cm−1) and C-O-C (1150–1000 cm−1). The alterations in the lignin fraction of aging samples (from the 9th and 12th centuries) were demonstrated by a reduction in the intensity of the bands at 1271 and 1232 cm−1 (Car-O) and the formation of new compounds, such as quinones and/or diaryl carbonyl structures, within the 1700–1550 cm−1 range. The SEM images of cedar wood samples from the 9th and 12th centuries reveal voids, indicating that the entire cell wall component has been removed, a characteristic feature of simultaneous white rot fungi. In addition, horizontal “scratches” were noted, indicating possible bacterial activity.