Fixation of Copper-Ethanolamine Wood Preservatives to Norway Spruce Sawdust

M. Humar,a* D. Žlindra,b F. Pohlevena

a University of Ljubljana, Biotechnical faculty, Department of Wood Science and Technology, Jamnikarjeva 101, SI-1000 Ljubljana, Slovenia.
Tel.: +386(0)14231161,
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b Slovenian Forestry Institute, Ljubljana, Slovenia.

Despite of the fact that copper-ethanolamine based aqueous solutions have been used for wood preservation for almost two decades, the complete mechanism of Cu-ethanolamine fixation is not completely understood. In order to elucidate interactions between copper-ethanolamine aqueous solutions and wood, Norway spruce (Picea abies) sawdust was immersed to 19 different copper based formulations. These solutions besides copper(II) sulphate contains ethanolamine and quaternary ammonium compound, sodium borate and/or octanoic acid. pH of this mixture was monitored for 4 h. Immersed sawdust was put to filter paper and washed with 1 L of distilled water. Leached impregnated wood sawdust was than oven dried (103 °C) and kept in dark and dry place until copper and nitrogen content were determined and correlated to pH changes of sawdust-preservative suspension during impregnation. The result showed that presence of ethanolamine makes fixation of copper in wood more effective. Copper absorption to sawdust is affected by concentration of copper, pH of the preservative solution and correlates with pH decrease during impregnation well. Furthermore, we proved that copper and nitrogen absorption to Norway spruce wood are connected as well. Understanding of this mechanism will enable experts to develop preservatives with better performance against weathering and wood pests.

Keywords: copper(II) sulphate, amine, octanoic acid, wood, wood preservation, fixation, absorption