The Effect of Nano-Silver (Ag) Treatment on The Drying Rate and Final Moisture Gradient of Poplar Wood

In this study, the effect of nano-silver (Ag) treatment on the drying rate and final moisture gradient of poplar wood was investigated. Poplar (Populous nigra) boards with green dimensions of 100×70×50 and 20 mm were treated with nano-silver
(Ag) suspension by spraying and immersion method. Two concentrations of
nano-silver suspension, including 20 and 100 ppm were used. Then, the boards
were conventionally dried at a constant dry-bulb temperature of 60 ^oC and relative humidity of 40%. The boards were coated on their four surfaces using epoxy resin to confine the moisture transfer along the board thickness. In addition, the temperature gradient along the board thickness was measured during drying. Results showed that in contrast to control samples, in the nanoparticles-treated boards, particularly those immersed in 100 ppm nano-silver, a reverse temperature gradient developed. The moisture gradient in the 50 mm-thick boards treated by 100 ppm nano-silver was more homogenous than that in control boards; however, no difference was found between the other treated boards and control boards. Despite reverse temperature gradient through the thickness of treated boards, there was no significant difference in drying rate between the control and treated boards. Thus, it can be claimed that in the medium temperature wood drying process, the temperature gradient cannot be considered as a driving force for moisture transfer and therefore the bulk flow due to temperature gradient (Soret effect) can be neglected.