Consumption of O2, evolution of CO2 and reduction of Cr(VI) during fixation of chromium based wood preservatives in wood

Norway spruce dust was impregnated with aqueous solutions of chromated copper wood preservatives. Immediately after treatment, observation of CO2 evolution and O-2 consumption were performed. Significant quantities of CO2 were released during reaction of chromium (K2Cr2O7) containing solutions with wood or brown rotted wood. Nevertheless, during reaction of cellulose with these preservatives we did not observe evolution of CO2. The presence of copper did not influence on concentration of CO2. Opposite to CO2 evolution, treatment of wood and brown rotted wood resulted in O-2 consumption. The oxygen concentration decrease in the measuring chamber was approximately 5 times greater than increase of concentration of carbon dioxide. Electron paramagnetic resonance (EPR) observations of chromium fixation showed that chromium is reduced from Cr(VI) to Cr(III) with Cr(V) as an intermediate on wood, brown rotted wood and cellulose. However, the reduction on wood and brown rotted wood was faster than the reduction on cellulose, as determined from changes of Cr signals in EPR spectra. So, evolution of CO2 and consumption of O-2 as well as EPR signals of Cr species thus indicate that brown rotted wood, consisting of lignin and hemicelluloses in contact with Cr(VI) reacts more intensively than cellulose, and possibly, oxidation mechanisms of lignin and cellulose with Cr(VI) are different.