Enhancing water repellency and decay resistance of wood by using water-soluble fractions separated from pyrolytic lignin of fast-pyrolysis bio-oil

Abstract

Biocides with lower environmental and human health impacts have been demanded by the society. Based on bioeconomy concepts, we investigated the potential of water-soluble fractions separated from the pyrolytic lignin of fast-pyrolysis bio-oil for wood protection against physical and biological agents. The high-viscosity crude bio-oil was fractionated in two oil-to-water ratios, 1:50 and 1:100, by separating the pyrolytic lignin and water-soluble fractions. Additionally, exfoliated nanostructures of bentonite were incorporated into water-soluble fractions to form bicomponent systems to improve the protection degree. These materials were then characterized in terms of morphological, chemical, and biological features. The preservative formulations were impregnated into pinewood (Pinus taeda), with subsequent evaluation of the morphology, wettability, thermal aspects, and antifungal activity of treated wood to determine the degree of protection. The water-soluble fractions severely impacted the water repellency of wood with contact angles up to 115°, and normal growth of the decay fungi (Trametes versicolor and Gloeophyllum trabeum). Also, the addition of nanobentonite in the formulations improved the action of the water-soluble fractions against the physical and biological agents, specifically for G. trabeum the decay can be decreased around three times compared to untreated wood. The combined action of water-soluble fraction and nanobentonite supported the wood water repellency with time-dependent stability of the contact angle and excellent antifungal activity, which is partially explained by the chemical composition of the water-soluble fraction and physical barriers formed by the nanobentonite on the surface. Therefore, a single use of water-soluble fractions or in combination with nanobentonite has potential for application as a bio-based wood protection process.