Marjeta Šentjurc

Changes in EPR spectra of wood impregnated with copper-based preservatives during exposure to several wood-rotting fungi

Summary The tolerance of various fungi against copper was examined. For this purpose, we impregnated Norway spruce (Picea abies) specimens with two different aqueous solutions: copper(II) octanoate with ethanolamine or copper(II) sulfate (cCu = 1.0 × 10−2 mol/l). Impregnated and unimpregnated test specimens were then exposed to brown rot fungi Antrodia vaillantii and Gloeophyllum trabeum or to white-rot fungi Schizophyllum commune and Trametes versicolor. After 2, 4, 6 and 12 weeks of exposure Electron Paramagnetic Resonance, Atomic Absorption Spectroscopy and mass loss measurements were performed. The results indicate that A. vaillantii, G. trabeum and T. versicolor transform copper(II) sulfate in wood into non-soluble, and therefore non-toxic, copper oxalate. The intensity of this reaction depends on the amount of excreted oxalic acid and was the highest for A. vaillantii and the lowest for T. versicolor. In the presence of ethanolamine, formation of insoluble copper oxalate was not possible and therefore, decay could not proceed. The major portion of copper remained in the wood and only minor amounts were in some cases translocated into nutrient media.

Influence of carboxylic acids on fixation of copper in wood impregnated with copper amine based preservatives

The importance of copper/amine based preservatives is increasing. Leaching of copper from wood preserved with these solutions is still higher than leaching from wood impregnated with copper chromium ones. In order to decrease leaching, different carboxylic acids (octanoic, 2-ethylhexanoic, decanoic) were added to copper/amine/boron aqueous solutions. An experiment of leaching of copper from Norway spruce was performed according to the modified standard procedure (EN 1250). Results confirmed that carboxylic acids significantly improve copper fixation. The best fixation was determined in specimens impregnated with the preservative solutions consisting of copper, ethanolamine, boric acid and octanoic acid. From such wood, only 1.6% of copper was leached.

Investigations of Ammoniacal Copper(II) Octanoate in Aqueous Solutions and its Determination in Impregnated Wood

Copper(II) octanoate in aqueous ammonia Solutions belongs to the group of relatively new environment friendly waterborne preservatives, arnmoniacaJ copper carboxylates. Electron paramagnetic resonance, EPR, was used to study the behaviour of Cu(II) octanoate in aqueous ammonia solution and in spruce sapwood, impregnated with this solution. From the comparison of EPR spectra of CuSCX and Cu(II) octanoate aqueous ammonia Solutions it was established that in the Cu(II) octanoate-water-ammonia System, Cu(II) remains in Cu(II) octanoateammonia complex. That means that the active substance in treatment of wood with this solution is copper(II) octanoate-ammonia complex and not tetraamminecopper(II). The samples of spruce sapwood were impregnated with l 10~mol/l copper(II) octanoate-waterammonia solution and EPR spectra of the dried samples were recorded. It was stated that in wood Cu(II) from Cu(II) octanoate-water-ammonia solution is complexated. After soaking the samples for 24 hours in the Cu(ll) octanoate aqueous ammonia solution, the radial penetration depth of 1.2mm for Cu(II) was determined. Preliminary experiments on leaching of the investigated substance showed that after first 24 hours of the experiment, copper concentration in the impregnated samples decreased for approximately 35 % and that subsequent leaching did not further change the Cu(II) concentration, within the detection limit.

Performance of Waterborne Cu(II) Octanoate/Ethanolamine Wood Preservatives

Summary Various aqueous wood preservative solutions containing Cu(II) in the form of copper(II) sulphate or copper(II) octanoate, ethanolamine and in one case octanoic acid were investigated by spectrophotometry, polarography and Electron Paramagnetic Resonance (EPR) spectroscopy. Results have shown the same coordination environment around Cu(II) in all solutions with ethanolamine. Computer simulation of the EPR spectra also revealed that the coordination in the first coordination sphere of copper is the same at low concentration of ethanolamine. At 20% ethanolamine concentration, a mixture of two complexes (one with two nitrogens and the other with three) could be detected. The active compound in the investigated ethanolamine containing solutions is the same when previously synthesised copper(II) octanoate was used, or when copper(II) sulphate and octanoic acid were utilized instead. Fungicidal and leaching experiments with the treated wood resulted in the same conclusion: it is not necessary to use pre-synthesised copper(II) octanoate for the preparation of waterborne copper/ethanolamine wood preservatives. Preservative preparation time and costs can be reduced by simply dissolving copper(II) sulphate and octanoic acid in aqueous ethanolamine solutions.

Influence of moisture content on EPR parameters of copper in impregnated wood

Influence of moisture content on Electron Paramagnetic Resonance (EPR) spectra of spruce wood impregnated with different, water-based copper solutions.

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

Abstract Norway spruce dust was impregnated with aqueous solutions of chromated copper wood preservatives. Immediately after treatment, observation of CO2 evolution and O2 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 O2 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 O2 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.

Influence of wood moisture content on the intensity of free radicals EPR signal

In this paper the influence of wood moisture content on the intensity of the free radicals electron paramagnetic resonance (EPR) signal in wood is described. Intensity of the free radicals EPR signal significantly correlates with wood moisture content.