Porosity and Pore Size Distribution of Native and Delignified Beech Wood Determined by Mercury Intrusion Porosimetry

Abstract

The complex hierarchical structures of biological materials in combination with outstanding property profiles are great sources of inspiration for material scientists. Based on these characteristic features, the structure of wood has been increasingly exploited to fabricate novel hierarchical and functional materials. With delignification treatments, the density and chemistry of wood can be altered, resulting in hierarchical cellulose scaffolds with enhanced porosity for the fabrication of novel hybrid materials. In the present study, focusing on acidic delignification of beech wood and its influence on porosity, we report on a structural characterization and qualitative assessment of the cellulose scaffolds using mercury intrusion porosimetry (MIP). To account for the effect of water removal from the hygroscopic structure, different drying methods—e.g., standard oven and freeze-drying—were applied. While native beech wood is characterized by the presence of macro, meso and micro pores, delignification altered the porosity, increasing the importance of the macropores in the pore size distribution. Furthermore, we showed that the final porosity obtained in the material is strongly dependent on the applied drying process. Samples delignified under harsh conditions at high temperature (mass loss of ~35%) show a 13% higher porosity after freeze-drying compared to oven-dried samples. The obtained results contribute to a better understanding of the impact of the delignification and drying processes on the porosity of cellulose scaffolds, which is of high relevance for subsequent modification and functionalization treatments.

Delignified Wood from Understanding the Hierarchically Aligned Cellulosic Structures to Creating Novel Functional Materials: A Review

“…Reproduced with permission. [118] Copyright 2019, Multidisciplinary Digital Publishing Institute. ultrastrong bulk materials based on DW.…”

“…Upon drying, the softened cell wall was more likely to collapse, promoting a “compacting” of the entire structure. [ 118 ] However, after freeze‐drying of DW, scaffolds of the cellular structure were relatively stable as they did not show collapsing behavior and maintained a porous structure (see Figure 6j–l). Further, they studied the influence of different drying on the porosity of DW.…”

“…In a recent study, Vitas et al. [ 118 ] evaluated the porosity and pore size distribution of natural and delignified beech wood using mercury intrusion porosimetry. The microstructure of the native and DW was also investigated using SEM.…”

Effect of the Drying Method of Pine and Beech Wood on Fracture Toughness and Shear Yield Stress

“…An effect of the drying method combined with the process temperature on physical properties of dried wood was studied by several researchers [ 3 , 11 , 12 , 13 , 14 , 15 ]. It was also reported that drying of wood may result in an increase of the material porosity, especially after delignification process, as investigated by Vitas et al [ 16 ]. An effect of the drying method on the parallel compressive strength of bamboo was reported by Arantes et al [ 17 ].…”

Enzyme immobilisation on wood-derived cellulose scaffolds via carbohydrate-binding module fusion constructs

“…Relatively mild pulping conditions can, however, remove the majority of lignin and hemicellulose whilst maintaining the native aligned porous structure of the original wood. [6][7][8][9][10][11][12] This aligned porous structure, which has been optimised by natural selection for the efficient transport of water-based solutions, has recently been exploited for applications such as epoxy resin composites, 6 radiative cooling materials 7 and water purification 10,11 among other applications. 12 Aligned porous structures hold certain advantages over non-aligned equivalents, including relatively low back-pressures needed to pass fluids over the active surfacea beneficial property for chromatography and other flow-based applications including continuous flow biocatalysis (CFB).…”