Abstract
Black locust (Robinia pseudoacacia L.), beech (Fagus sylvatica L.), aspen (Populus tremula L.) and sessile oak (Quercus petraea Liebl.) hardwood samples were irradiated by a strong ultraviolet (UV) emitter mercury lamp at 50 °C. Other series of specimens were exposed to a combined treatment of UV irradiation and water leaching. Ratio of UV radiation and water leaching time was 2:1. While the total duration of UV radiation was 20 days for both test series that of water leaching was 10 days. IR measurement was taken after both UV radiation and water leaching to monitor both effects separately. Lignin degradation proved to be more intensive in leached samples than in purely UV-irradiated samples. Guaiacyl and syringyl lignin showed similar degradation properties. Unconjugated carbonyl groups generated by the photodegradation were the most sensitive chemical components to leaching. Photodegradation generated two absorption bands of unconjugated carbonyl groups at around 1710 and 1760 cm−1 wavenumbers. The band at 1760 cm−1 was much more sensitive to water leaching than the band at 1710 cm−1. Three to ten days of water leaching was enough to remove all unconjugated carbonyls generated by the photodegradation, depending on the species. Sessile oak was the most sensitive species to water leaching, whereas black locust proved to be the most stable against both photodegradation and water leaching. Water was able to leach out unconjugated carbonyl groups (absorbing at 1745 cm−1) originally present in all investigated wood species.
Highlights
Wood is a renewable material bonding large amounts of carbon
The results showed that the unconjugated carbonyl groups were partly leached out by water
UV radiation time was 24 h, followed by water leaching for 24 h, while in the second cycle, UV radiation time was doubled; 48-h UV radiation was followed by 24-h water leaching
Summary
Wood is a renewable material bonding large amounts of carbon. Growing trees absorb carbon dioxide from the atmosphere and convert it to woody biomass (Bravo et al 2017). Half of the total wood mass is bonded carbon absorbed from the atmosphere. Taking into account the forested area of our planet, a significant amount of carbon can be stored in wood material for decades or even centuries, depending on the application. Whether trees naturally decompose or burn, carbon dioxide is emitted back into the atmosphere. Carbon storage may be prolonged applying wooden products with longer life cycle. It is, in our common interest to ensure the longest possible life cycle for our wooden applications (Geng et al 2017)
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