Microstructure of wood char

Zicherman, Joseph B.; Williamson, R. B.

doi:10.1007/bf00351372

Cited by 4 publications

(3 citation statements)

References 8 publications

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“…We hypothesize that native PAHs are predominantly sorbed in or to the charred exterior of charcoal particles, the exact location where they are produced. Charcoal is however known to possess deep narrow pores (43) (see also Table 1). Added chemicals may penetrate these pores to reach areas where they can sorb to high(er) affinity sites (e.g., narrow restricted pores with molecular dimensions) which causes elevated K S D-PAH values.…”

Section: Resultsmentioning

confidence: 99%

Sorption of Polycyclic Aromatic Hydrocarbons and Polychlorinated Biphenyls to Soot and Soot-like Materials in the Aqueous Environment: Mechanistic Considerations

Jonker

Koelmans

2002

Environ. Sci. Technol.

546

577

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Recent studies have shown that sorption of polycyclic aromatic hydrocarbons (PAHs) in soot-water systems is exceptionally strong. As a consequence, soot may fully control the actual fate of PAHs in the aquatic environment. However, sorption has only been characterized for a limited number of PAHs to diesel soot, and the mechanism is poorly understood. In this paper, we present an extensive data set of sorbent-water distribution coefficients (K(S), n = 236) for a series of PAHs (both native and added) and polychlorinated biphenyls (PCBs) to five different types of soot and five soot-like materials. Both Ks values and physicochemical properties of the sorbents show large variation. In general, sorption is very strong, with K(S) values up to 10(10), showing the highest distribution coefficients on a mass basis ever reported. Sorption of in particular PAHs is often over 1000 times as strong as sorption to amorphous sedimentary organic carbon. The variation in K(S) values cannot be explained by "soot carbon fractions" or specific surface areas of the sorbents. Instead, values for native PAHs are mostly determined by the sorbates' molar volume, and values for added PAHs and PCBs are determined by the sorbents' average pore diameter. From differences in K(S) values between native and added PAH analogues, it can be deduced that generally more than 50% (with values up to 97%) of the native PAH concentration in soot is not available for distribution to the aqueous phase. We conclude that this is caused by physical entrapment of the chemicals within the solid matrix. Furthermore, most sorbents appear to preferentially sorb PCBs with planar configurations, a phenomenon most likely driven by sorption in molecular-sized pores. Pore sorption is also concluded to be the most important sorption mechanism for added PAHs together with pi-pi interaction processes with flat aromatic sorbent surfaces. Frequently observed, slowly desorbing, resistant contaminant fractions in sediments may very well be explained on the basis of these results.

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Section: Resultsmentioning

confidence: 99%

Sorption of Polycyclic Aromatic Hydrocarbons and Polychlorinated Biphenyls to Soot and Soot-like Materials in the Aqueous Environment: Mechanistic Considerations

Jonker

Koelmans

2002

Environ. Sci. Technol.

546

577

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“…Flaked area is 0%, and cracked area 20% (includes also smaller cracks scaled as 1 and 2) increase dimensional stability. Instead, a stressed transition layer is formed, as discussed in Zicherman and Williamson (1981), where the origin of surface cracks was traced to the pyrolysis zone beneath the char surface where evaporation and cooling change drastically over few cell layers.…”

Section: Cracking and Flakingmentioning

confidence: 99%

“…The char layer thickness, as well as several other properties of the char, depend heavily on the technique used, namely temperature and modification time. Similarly, wood species has a great effect since the cell structure of char is similar to the original unmodified wood (Zicherman and Williamson 1981), meaning that pores and cells retain their shape and size. For example, spruce still shows pit aspiration that reduces the permeability compared to, for example, Scots pine (Kymäläinen et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Natural weathering of soft- and hardwoods modified by contact and flame charring methods

2022

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Exterior cladding boards benefit from a known service life that makes planning of maintenance and replacement procedures easier. Among the different wood modification methods, surface charring of wood is expected to increase the lifespan of wooden elements in building façades. This paper reports the properties of surface charred Norway spruce, Scots pine and Silver birch in Southern Finnish climate over a natural weathering period of one year. Several modifications were examined, namely variants of contact and flame charring. These also included oiled and brushed surfaces. The flame charred samples of spruce and birch withstood the weathering well, with some minor flaking and cracking. The thick pine samples cracked extensively regardless of modification, raising questions on suitable density and thickness of wood destined for a charring modification. Contact charring did not seem suitable for outside uses at least in direct sunlight, as the colors faded, and surfaces cracked within all examined groups. The spectroscopical methods employed also revealed degradation of contact charred wood lignin, whereas the flame charred surface consisted mostly of recalcitrant carbon structures rather inert towards weathering. This highlights the importance of sufficient structural degradation of wood components in creating a weathering resistant surface, and also shows that a thicker thermally modified layer does not necessarily improve the weatherability in contact charred wood.

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Abiotic Degradation of Wood

Reinprecht¹

2016

Wood Deterioration, Protection and Maintenance

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Microstructure of wood char

Cited by 4 publications

References 8 publications

Sorption of Polycyclic Aromatic Hydrocarbons and Polychlorinated Biphenyls to Soot and Soot-like Materials in the Aqueous Environment: Mechanistic Considerations

Sorption of Polycyclic Aromatic Hydrocarbons and Polychlorinated Biphenyls to Soot and Soot-like Materials in the Aqueous Environment: Mechanistic Considerations

Natural weathering of soft- and hardwoods modified by contact and flame charring methods

Abiotic Degradation of Wood

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