Fixation of copper(II)-protein formulation in wood: Part 1. Influence of tannic acid on fixation of copper in wood

A new waterborne CuSO4 center dot 5 H2O-based formulation containing proteins from animal plasma SOLUTEIN (0.1 %) as additive was investigated. Scots pine sapwood powder, cellulose and lignin were impregnated with solutions containing 0.1 % and 2.5% copper (w/v). After impregnation, the samples were additionally treated by air-drying at 100 degrees C or by tannic acid for denaturation of the proteins. Copper concentration was determined by atomic absorption spectroscopy and electron paramagnetic resonance (EPR). Copper introduced into wood by impregnation and eliminated by leaching was controlled. The maximum retention of 5.83 g kg(-1) in wood was obtained when wood was treated with tannic acid (2.5%) after impregnation. For a formulation containing more than 0.5% of CuSO center dot 5 H2O, precipitation of the salt in wood appears. Five different EPR spectra appeared in wood, cellulose and lignin after treating with SOLUTEIN and with tannic acid.