Investigation of copper solubilization and reaction in micronized copper treated wood by electron paramagnetic resonance (EPR) spectroscopy

Abstract

The purpose of this study was to compare the reaction chemistry of micronized copper and alkaline copper treatments with wood and to determine how fast copper is solubilized during the reaction between the acidic functionality in wood and the basic copper carbonate (CuCO 3 ). Copper species produced in wood by various treatment methods were analyzed by electron paramagnetic resonance (EPR) spectroscopy. The effects of time and solution concentration on the spectral parameters of copper complexes in sawdust treated with copper sulfate solutions were examined, followed by study on the structure and the rate of formation of the copper complexes in sawdust treated with basic CuCO 3 suspension. The study further attempted to identify the soluble copper species formed in wood during treatment with micronized copper preservatives. Comparisons were made among the fi xed copper complexes in wood treated with micronized copper preservatives, copper sulfate solutions, basic CuCO 3 suspensions and alkaline copper solution. The results showed rapid formation of fi xed copper complexes in wood treated with aqueous suspensions of basic CuCO 3 . These complexes can resist leaching, and they have similar stereochemistry to those formed between wood and copper sulfate. This fi nding supports the premises that soluble copper is generated during the treatment of sawdust with basic CuCO 3 , and it can bond to wood cell components by migrating into the cell wall in a manner similar to other soluble copper species. Such copper complexes formed are different from those of alkaline copper treated wood, which can be easily distinguished by EPR.

Quantification of mobilized copper(II) levels in micronized copper-treated wood by electron paramagnetic resonance (EPR) spectroscopy

“…The spectra of the Cu complexes exhibited g z values of ∼2.382 and A z tensors of ∼130 G, which were typical of the Cu-wood complexes formed with only Cu-oxygen bonding (Hoffmann et al 2008). They were also similar to those of commercial MCQ-treated samples (Xue et al 2012). The Cu contents of the samples determined by XRF were plotted against the corresponding EPR intensities and a linear correlation coefficient (R 2 ) of 0.995 was found (Eq.…”

“…Cupric ions have been detected in the laboratory leaching of the MC quat (MCQ)-treated wood (Zhang and Ziobro 2009;Stirling and Morris 2010). A recent study (Xue et al 2012) has shown that the wood treated with an aqueous suspension of BCC produces soluble hydrated Cu species, which rapidly react with wood components resulting in Cu-wood complexes very similar to those formed by the treatment of the wood with copper sulfate (CuSO 4 ) solutions. However, the amount of the mobilized copper(II) (Cu mob ) level in the MC-treated wood has not previously been established because of the difficulty in differentiating the Cu mob from the total Cu present after treatment.…”

“…On the contrary, BCC is an antiferromagnetic material (Janod et al 2000), whereas the Cu-wood complexes formed in the wood after treatment contain paramagnetic cupric ions (Hughes et al 1994;Xie et al 1995). The differing magnetic behavior of the two Cu species enables the determination of the mobilized and chemically fixed cupric ions by means of electron paramagnetic resonance (EPR) spectroscopy (Xue et al 2010(Xue et al , 2012. The spectroscopic characteristics of the cupric species in sapwood treated with MC and CuSO 4 are identical.…”

Reacted copper(II) concentrations in earlywood and latewood of micronized copper-treated Canadian softwood species

“…Detailed methodology was reported by Xue et al (2012Xue et al ( , 2013. A series of sawdust samples treated with CuSO 4 solutions at 16 different concentrations was analyzed by EPR.…”

“…However, electron paramagnetic resonance (EPR) spectroscopy is able to perform this task because BCC is antiferromagnetic and EPR silent. Earlier studies (Xue et al 2010(Xue et al , 2012 confirmed that hydrated Cu species were produced and fixed rapidly with wood upon treatment with an aqueous suspension of BCC. A quantification method based on EPR in combination with X-ray fluorescence (XRF) spectroscopy was developed for determining the reacted Cu concentrations in the treated wood (Xue et al 2013).…”