Impregnation of wood with water using ultrasonic irradiation and water containing bulk nanobubbles

This paper investigates the impregnation of Japanese cedar (Cryptomeria japonica D. Don) with water using ultrasound irradiation, followed by immersion in water containing bulk nanobubbles (NBs). Cavitation bubbles generated during ultrasound irradiation mechanically remove extractives from the wood surface, enhancing the mass transfer of water into the wood. Water containing bulk NBs has a lower surface tension compared to pure water, enabling superior permeability into narrow spaces. However, the application of water containing NBs for wood impregnation post-sonication remains underexplored. In this study, wood was subjected to ultrasound irradiation at 38 kHz, followed by immersion in water containing bulk NBs, to determine the optimal sonication time and NB concentration for efficient impregnation. The results indicate that water uptake by the wood initially increases and then decreases with increasing NB concentration and sonication time. Optimal sonication time and NB concentration resulted in highly efficient impregnation.