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Interaction of Copper-Containing Preservatives with Wood. Part 1. Mechanism of the Interaction of Copper with Cellulose
Holzforschung
Abstract
In the present work. the stare of the copper ions absorbed by cellulose from aqueous solutions with different pH values has been studied by electron spin resonance (ESR), X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray analysis (EDXA) methods, It has been shown that the curve of copper sorption has a S-like shape characteristic for weak acid sorbents. At all pH values in ESR-spectra, an anisotropic Cu(II)-signal is registered. At pH >4, the anisotropy of ESR-spectra decreases. At pH = 10, complexes connected by exchange interactions and diamagnetic clusters are formed. After the leaching of specimens, the ESR-signal practically disappeared. The decrease of the copper content in cellulose did not correlate with the change of the integral intensity of the spectra. The changes in ESR-spectra of copper-containing cellulose after leaching were explained by the formation of the Cu(II) diamagnetic clusters.
... For the treated samples, the band density at 1743 cm −1 has a slight reduction. The reduction of the band is attributed to the reactions between copper and carboxylic groups that have taken place, while the cellulose acts as a stabilizer of the Cu-NH complex in solution [19][20][21][22][23]. ...
In spite of some studies about the wood permeability and its improving measures, some progress has been made to study the diffusion and transmission of preservative solutions in standing trees. In the present study, copper- (Cu-) based preservative with other reagents is injected into the standing tree Chinese fir using sap-flow method. The chemical compositions of the retreated woods are analyzed with Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The samples from different height positions are analyzed with scanning electron microscope (SEM) and atomic absorption spectroscopy (AAS) to obtain microstructures and preservative retention, respectively. The results indicate that the preservative solutions with lower concentrations are more conducive to diffusion and transmission in the wood. Moreover, the preservative retention at different height position has a greater concentration gradient for composite preservative solutions than those of the single preservative solutions. Solidified preservative particles are observed in xylem rays with SEM. The results of the present study provide some useful information for the functional design of the target wood products.
... The interaction of cellulose with Cu 2? and Ca 2? ions has been thoroughly studied by many authors (Acemioglu and Alma 2001;Druz et al. 2001;Norkus et al. 2004;Saito and Isogai 2005;Sundman et al. 2008;Fitz-Binder and Bechtold 2012;Emam et al. 2012;Ozturk et al. 2009;Nikiforova and Kozlov 2012). According to the literature, Ca 2? ions react with carboxyl groups of cellulose in a 1:1 ratio through an ion exchange mechanism (Sundman et al. 2008;Ozturk et al. 2009;Fitz-Binder and Bechtold 2012). ...
Viscose fibers were treated with atmospheric pressure dielectric barrier discharge (DBD) plasma obtained in nitrogen in order to activate the fiber surface prior to sorption of the divalent ions Ca2+ and Cu2+. Methylene blue sorption was used for estimation of carboxyl group formation on the surface after DBD plasma treatment, through the degree of fabric staining (K/S). Sorption of divalent ions was performed from solutions of each individual ion and from solutions of calcium and copper in succession onto untreated and plasma-treated viscose samples. The quantity of sorbed metal was determined from the neutralization and iodometric titration method. Scanning electron microscopy coupled with energy dispersive X-ray analysis was used for fiber morphology and surface characterization before and after plasma treatment, and after metal ions sorption. Experiments revealed copper microparticles formation on the fiber surface when sorption of copper was performed on samples with bonded calcium. Further analysis confirmed that for growth of copper particles, both calcium ions and nitrogen DBD plasma pretreatments are necessary.
... Copper contained in water extracts and solid materials after extraction was tested by atomic absorption spectrometry (AAS) and also electron paramagnetic resonance spectroscopy (EPR) was employed. By EPR, it is possible to distinguish between various types of copper complexes formed in wood and its components (Hughes et al. 1994; Xie et al. 1995; Druz et al. 2001; Humar et al. 2002). ...
A new waterborne CuSO4•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°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•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.
... Only a small portion of copper can react with cellulose to form new compounds through formation of hydrogen bonds between a cellulosic hydroxyl group and amine nitrogen (Druz et al., 2001). ...
In order to improve the leaching resistance of active ingredient-copper in ammoniacal copper quat-type D (ACQ-D) treated Chinese
fir (Cunninghamia lanceolata Hook.), microwave post-treatments were carried out. The percentages of leached copper from ACQ-D treated Chinese fir with
different microwave post-treatments were obtained after leaching tests by analyzing the copper retention in treated wood.
The fixation mechanism of copper in the treated wood was determined with the help of SEM and FTIR spectra, while the valence
conversion of copper after microwave post-treatments was studied by UV spectroscopy. Our experimental results show that the
percentage of leached copper was reduced significantly after microwave post-treatment over time. This development was reinforced
by allowing even more time for the treatment as well as with an increase in the power of microwave post-treatment. The leaching
resistance of copper in wrapped samples was better than that in unwrapped samples, which is attributed to the combined effects
of temperature and moisture content. Compared with air-dried samples, the valence conversion in the samples with microwave
post-treatments changed slightly, which demonstrates that microwave post-treatments cannot impair the natural decay resistance
of ACQ-D treated wood. SEM and FTIR spectra showed the presence of crystal particles formed by chemical reactions between
copper and wood ingredients in wood cell walls and wood pits. Only a small amount of copper reacted with cellulose, while
lignin and hemicellulose were the major bonding sites for copper in wood. Given the experimental results of mechanical properties,
microwave post-treatments had a slight effect on the compression strength parallel to the grain and on the crystallinity of
ACQ-D treated Chinese fir.
... Chromate copper arsenate was completely banned in the European Union and limited to nonresidential uses in the United States [2]. As a result, CCA alternatives such as ammoniacal Cu quaternary (ACQ), Cu bis-(N-cyclohexyldiazeniumdioxy) (Cu xyligen), amine-Cu formulations [3][4][5], and Cu-azole-based preservatives (CuAz) [6] have been developed and used in several countries. However, CCA alternatives have been more expensive than CCA and are characterized by increased leaching of Cu from wood products [7]. ...
Okara, an organic waste product obtained from soy milk production, was used with copper chloride or sodium borate to formulate new wood preservatives as a substitute for expensive wood preservatives, such as copper-azole-based preservatives and ammoniacal copper quaternary. Before formulating the preservatives, okara was hydrolyzed by enzymes (cellulase, pectinase, and protease) to augment penetration and fix the biocide salts of the preservatives into wood blocks. The preservatives were injected into wood blocks by vacuum pressure to measure the treatability of the preservatives. The treated wood blocks were placed in hot water for 3 d to measure leachability. The treatability and leachability of the preservatives were affected by the type and loading amount of enzymes and the addition of sodium borate into okara-based wood preservative formulations. The treatability and leachability of the preservatives formulated with copper chloride and okara hydrolysates were 63.38 and 3.15%, and those of the preservatives with copper chloride, okara hydrolysates, and sodium borate were 61.47 and 3.32%, respectively. Despite the hot water leaching, wood blocks treated with preservatives formulated with 2% cellulase, pectinase, and protease hydrolyzed okara, CuCl(2), and sodium borate showed only 1.98% average weight loss against Fomitopsis palustris over 12 weeks. Microscopic observation revealed how okara-based preservatives work in wood blocks. Okara has potential as a raw material for cost-effective and environmentally friendly wood preservatives.
Micro-based wood preservatives have tremendous potential for reducing in-service preservative losses thereby reducing the amounts needed for protection. Enhancing micro-based wood preservatives/wood interactions without negatively affecting performance could help further enhance the properties of these materials. The factors affecting the leaching and decay resistance of the micro CuO/silica sol wood preservative and the mechanism of action of the preservative and wood were analyzed using scanning electron microscopy/energy dispersive X-ray analysis, Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction for both steaming and freezing post-treatment. SEM showed that the preservative had an irregular spherical shape with an average diameter of 0.45 μm. Changes in moisture content and pH were factors affecting preservative leaching and blocks decay resistance. FTIR analysis showed that the interaction between preservative and wood occurred in wood cellulose and lignin, and freezing treatment enhanced this interaction, which was the reason why freezing treatment improved preservative leaching resistance.
It is the preconditon for structure design and performance-prebuild of Chinese fir/nano-Al2O3 composite to characterize the structure of Chinese fir/nano-Al2O3 composite and analysis combining mechanism of Chinese fir with nano-Al2O3 particles. The structure characterization of the composite was studied via SEM, and TEM, while mechanism analysis via EDXA and other spectroscopy etc in this paper. The research shows that nano-Al2O3 particles distribute on cell-wall of the wood, and the non-saturation groups on surface of nano-Al2O3 particles can be easily combined firmly with hydroxide radicel etc in the wood; and parts of them are sinked into the nano-space inside the wood, while some hydroxide radicel of nano-Al2O3 particles condensated between each other to form a net-structure and also some others in-situ polymerized and filled into the structure.
By combining the organic-groups inside Chinese fir with nano SiO2 particles in a way similar to natural biological mineralization, Chinese fir/nano SiO2 composite can be obtained. The improvement of mechanical performances, etc. is dependent on the interface and the combining situation between them. Based on duality composite theory, the structure characterization of the composite was studied with SEM and TEM, and the combining mechanism was analyzed with XRD and EDXA, etc. The results have shown that nano SiO2 particles distribute on cell-wall mostly in nano-size level, and part of them sink into the nano-space inside the wood. The un saturation groups on the surface of nano SiO2 particles can be easily combined with hydroxide radicel etc. in the wood. Not only the in situ synthesizing appears inside Chinese fir, but there are also mainly chemical reactions or links between the large sum of un-saturation active keys, free hydroxy groups on the face of nano-particles and the hydroxy groups of cellulose, hemi cellulose inside Chinese fir wood.
Several new copper(II) complexes with guaiacyl lignin models vanillin (HL1) [Cu(L1)2(nia)2] (1) (nia = nicotinamide) or vanillic acid (HL2) [Cu(L2)2(nia)2] (2) [Cu2(μ-L2) 4(nia)2] (3), and [Cu(L2)2(Hetam)2] (4) (Hetam = ethanolamine) were isolated and characterized. The molecular structure of complex 1 reveals bidentate vanillin (HL1) coordination via the methoxy and the deprotonated hydroxy groups. On the other hand, the vanillic acid (HL2) complexes 2-4 show a deprotonated carboxylate group with chelating coordination mode in 2, bridging in 3 and monodentate coordination in 4. The mononuclear complexes 1, 2 and 4 show a distorted trans octahedral coordination sphere with pairs of monodentate and chelating ligands. A replacement of the monodentate nicotinamide ligand in 2 with the bidentate ethanolamine ligand in 4 changes the coordination mode of the vanillic acid anion from bidentate (complex 2) to monodentate (complex 4). This shift inside the coordination sphere reveals different Q-Cu-O Jahn-Teller axes by the vanillic acid anion in 2 and ethanolamine in 4. Empty channels are present in the crystal structure of the dinuclear complex 3, stabilized by hydrogen bonds and π-π stacking.
The objective of this paper is to use the modified nano-calcium carbonate compositing directly or sot-gel compositing with poplar wood by the vacuum infusion methods to prepare new environmental materials. This paper introduces promotion effects of nano-technology on the development of fast-growing poplar wood, the problems and research of fast-growing poplar wood compositing with nano-materials. By preparing the new environmental materials, we implement the use of plantation timber to produce high value-added products, and the use of a variety of nano-technology to improve the performances of wood, and improve timber utilization.
The reactions between constituents of alkaline copper quat (ACQ) and of wood were investigated by a tensile stress relaxation approach. Small samples were stressed and impregnated with various ACQ solutions, in which the ratios of monoethanolamine (MEA), ACQ, and didecyl dimethyl ammonium chloride (DDAC) were varied. The other parameters included temperature and concentration of the treating solutions. The stress relaxation curves of wood were recorded during the impregnation period and the effects of impregnation parameters were investigated by an orthogonal experimental design (OED). The effects of water, MEA, and DDAC on stress relaxation of the samples were also observed. The bulking effect of water was tested separately in samples treated with distilled water without stretching. The results showed that the stress relaxes dramatically in the initial period and then changes slightly over a long period, which is readily visible in double logarithmic plots of f (t)/f (0) versus time (t). There are complex interactions between the components of ACQ solutions and wood matrix: (1) in rapid phase I, the splitting of the easily accessible hydrogen bonds (mainly in the amorphous hemicelluloses) are prevalent by interaction with components of ACQ solution; (2) in slow phase II, Cu penetrates deeper in less accessible regions (e. g., in paracrystalline regions of cellulose) and renders possible further relaxation. The results of range and variance analysis reveal that the molar ratio of Cu to MEA and temperature of ACQ solution have significant effects on the rate of reaction during phase I, whereas in phase II only the temperature of ACQ solution has a significant effect. The stress relaxation curves of samples impregnated in water, MEA, and DDAC all showed a quasi one phase stress relaxation rate, which suggests that phase II is mostly related to Cu in ACQ formulations. It is concluded that the formation of complexes with Cu is still the major reaction in wood although there is competition among ACQ constituents for reaction sites.
The experiments were carried out on the wood preservative with a strong fungicidal activity based on Cu(II) carbonate, 2-aminoethanol (monoethanolamine) and quaternary ammonium compound (QAC). The object of the performed investigations was sapwood of Scots pine (Pinus sylvestris L.) treated with Cu-EA-QAC formulation. Mycological investigations were carried out according to EN 113 and EN 84 standards. The retention of the copper ions in the wood grows nonlinearly with concentration (in %) of the impregnating solution from 0.25 kg/m(3) at 0.03% to 1.55 kg/m(3) at 0.21% (i.e. nearly six times), whereas the copper leachability decreases 2.5 times from 15% to 6% in the same range. These results indicate good fixation of the copper to the wood and high leaching resistance. EPR results and computer simulations of the observed EPR spectra show that in Cu-EA aqueous solution the Cu(EA)(2)(H2O)(2) complexes exist and the main coordination plane is not destroyed in the impregnating solution and in the wood. In Cu-EA-QAC solution the Cu(EA)(2)(QAC)(2) complexes appear, whereas EPR spectra of the treated wood indicate coexistence of a few types of Cu-complexes. We have noted strongly fixed Cu(EA)(2)O-2 and Cu(EA)(2)O complexes with oxygen atoms from wood functional groups.
Electron paramagnetic resonance (EPR) spectra were recorded for copper(II) ions in cellulose, lignin and pine sapwood impregnated with a water based formulation containing CuSO4•5 H2O, tannic acid and animal protein SOLUTEIN. EPR parameters were derived from computer-simulated spectra. The parameters were interpreted in terms of molecular orbital theory giving coefficients of spin delocalization onto ligands. Five different spectra of chemically fixed complexes were identified. The complexes were octahedral with a different degree of elongation. For a copper concentration higher than approximately 0.5%, the additional EPR signal from the precipitated CuSO 4•5 H2O salt appears. Two possible coordination sites are proposed for fixed copper complexes in cellulose structure and a single site is proposed for copper in a lignin. These complexes are different from the copper complex in wood, where Cu(H2O)4O2 octahedral complex exists with apical coordination to two oxygen atoms of deprotonated hydroxyl groups of polymeric units. When tannic acid is added to the impregnating solution, copper ions are strongly coordinated in a square-planar geometry of CuO4 and are easily leached. The copper-SOLUTEIN complex yields a distinguished EPR spectrum only in the impregnating solution, but not in the wood. Except for the copper(II) EPR spectra, where the signals from free radicals were detected in wood and lignin with a concentration in the order of magnitude of 1017 g-1 dependent on wood treatment.
Fixation of copper ions to acetoacetylated wood meal (AAWM) was conducted in Cu(OAc)(2)-MeOH solution. The maximum amount of copper fixed to AAWM was 147.9 mg g(-1) under optimum conditions. From FT-IR analyses of AAWM containing copper ions (AAWM-Cu), it was concluded that a chelate was formed between copper and the acetoacetyl group of AAWM. In a leaching test, half of the copper in AAWM-Cu was retained, even at pH 4.0.
Interaction of Cu(II) with cellulose pulp was studied by means of polarography, AAS, and ultraviolet–visible spectrophotometry. The experiments were carried out at room temperature and at selected initial cellulose pulp slurry pH values between 7.0 and 13.0.The results obtained showed a trend of decreasing pH after chemical degradation of the pulp (2% w/w) as well as after further addition of a Cu(II) salt (0.5 mmol l−1; pCu=3.3). The pCu in solutions with initial pH values from 7.0 to 11.0 remained in the range 3.4–3.9, implying insignificant complexation of Cu(II). This is almost certainly caused by the relatively low solution pH (5.9–7.4) after pulp treatment and Cu(II) salt addition. When the pH of these solutions was raised to 12.0, the complexing ability of the dissolved cellulose degradation products rises, apparently, due to the deprotonation of hydroxyl groups, and pCu reached 13.0–13.5.When the Cu(II) salt was added directly into cellulose pulp slurry at the onset of the alkaline treatment, some of the Cu(II) ions were bound (due to adsorption and/or chemical bonds formation) to the cellulose fibres. The extent of this interaction depended on the initial pH. The bound fraction of the Cu(II) ions represented about 50–70% of the initial Cu(II) amount at pH 7.0 and about 90–95% at pH 13.0. The pCu in filtered solutions with initial pH values in the range 7.0–11.0 remained in the range 3.9–6.1. When the pH of any of the solutions that had initial pH values between 7.0 and 11.0 was increased to 12.0, the complexing ability rised dramatically, and pCu reached 12.9–15.1.
Optical and electron paramagnetic resonance (EPR) spectra were recorded for a series of Cu(II) complexes with monoethanolamine
(EA) and the quaternary ammonium compound (QAC) alkyldimethylbenzylammonium chloride in aqueous solution with H3BO3 which are tested as modern impregnating solutions for wood preservation. It is proved that in aqueous solutions of Cu-EA
the octahedral complexes I, Cu(EA)2(H2O)2, exist with water in apical positions. The addition of the QAC results in an exchange of water for nitrogen of the QAC molecules
with a possible partial destruction of the coordinating molecule (complex II). The detailed electronic structure is determined
for both species I and II. Boric acid does not influence the complex structures. In the treated wood (Pinus silvestris L.) the complex I is destroyed and Cu(EA)2 is attached to the OH groups of cellulose molecules, forming a stable complex. The complexes II still exist in wood, but
with higher-concentration impregnating solution a part of these complexes is destroyed by coordination to the OH groups of
cellulose molecules.
The enzymatic degradation of recalcitrant plant biomass is one of the key industrial challenges of the 21st century. Accordingly, there is a continuing drive to discover new routes to promote polysaccharide degradation. Perhaps the most promising approach involves the application of "cellulase-enhancing factors," such as those from the glycoside hydrolase (CAZy) GH61 family. Here we show that GH61 enzymes are a unique family of copper-dependent oxidases. We demonstrate that copper is needed for GH61 maximal activity and that the formation of cellodextrin and oxidized cellodextrin products by GH61 is enhanced in the presence of small molecule redox-active cofactors such as ascorbate and gallate. By using electron paramagnetic resonance spectroscopy and single-crystal X-ray diffraction, the active site of GH61 is revealed to contain a type II copper and, uniquely, a methylated histidine in the copper's coordination sphere, thus providing an innovative paradigm in bioinorganic enzymatic catalysis.
Metal binding to an organic peat soil was probed by paramagnetic doping with copper, chemical modifications of the organic matter in the soil, and 13C CP-MAS NMR spin lattice relaxation rate measurements. Carboxyl and hydroxyl functional groups were determined to be most significant in copper uptake by the unmodified soil. Esterification and acetylation of the soil showed that metal binding by carbohydrate structures occurs independently of other functional groups and may even induce a pseudochelation phenomenon. Sorption isotherms corroborate the importance of carbohydrate structures in metal binding. These results suggest that environmental modeling of metal binding and retention in soils should incorporate estimates of the distributions of all functional groups in the soil organic matter (e.g. aliphatic, carbohydrate, phenolic, carboxyl) and their relative binding strengths.
The possible nature of covalently-bonded compounds and of coordination complexes between Cr(VI) (as CrO4=) or Cr(III) of CCA/CCB preservatives and lignin in wood is examined by theoretical means. Of the two complexes originally traced by Hon and Chang (1985) one has been found to be a covalently-bonded compound the structure of which has been confirmed by solid state C-13 NMR. The second one is a coordination complex that does not appear capable of transformation into the first as initially thought (Hon and Chang 1985). The total apparent effect of transformation between the latter complex and the former covalently-bonded compound is ascribed to their joint copolymerization to form guajacyl units/polychromates copolymer networks. This characteristic appears to be only allowed with model compounds and with lignin derivatives in solution (such as ligonsulphonates) and appears to depend from both the amount of total Chromium and of Cr(VI) available. The quantities of Cr normally used in the CCA treatment of wood as well as its partial reduction to Cr(III) by the wood carbohydrates, should not allow the formation of a polymer network in treated wood to any great extent, if at all or, when it does, it is likely to be mostly or only through Cr(III) coordination complexes of Cr(VI)/guajacyl covalently-bonded units.
On contact of a Cu-Cr-As preservative with wood there is a sudden extensive increase of the pH. This is explained by ion-exchange and adsorption reactions with the wood. The presence of wood drastically changes the conditions for precipitation compared to a pure solution system. The pH increases up to a maximum during the main fixation period, then periods of alternating slow pH decrease and pH increase follow until the pH reaches its final value. Dissociation of actual acid species, kinetics, oxidation by chromic acid and precipitate formation likely to occur are generally discussed as a background to the subsequent parts II and III of the investigation.
The chelation of copper(II) ion with a hydrophilic resin prepared from a polyacrylamide matrix with attached thiol groups was compared with that of a low molecular weight analog. The formation of Cu(I) complexes through a redox reaction between Cu(II) ions and thiol groups was demonstrated by ESR spectroscopy and electrochemical measurements. The macromolecular structure of the resin allows Cu(I) to oxidize slowly through contact with air. The determination of ESR parameters suggests that the copper(II) environment at this time is S-S-O-O.
The kinetic behavior of a Cr6+/Cu2+ system in its reaction with wood has been elucidated. The same reactions with carbohydrates and lignin of wood for CrVI alone are still present. Approximately 20% of the copper is fixed to the guaiacyl units of lignin in the form of copper chromate; the remaining copper forms complexes with cellulose and mainly with the guaiacyl units of lignin. The CrVI/lignin guaiacyl unit complexes already found for the treatment of wood with CrO3 are still the main CrVI complexes formed. Copper chromate is present as [Cu(H2O)2(guaiacol)]CrO4(guaiacol) complexes, and CuCrO4 bridges between different guaiacyl units of the lignin network appear to be likely. Substantial interference of the Cu2+ ions in the second-zone reactions of CrVI with wood occurs. The amount of CrVI and CrIII fixed onto lignin and cellulose compares well with experimental values. Rate constants, energies of activation, and Arrhenius equations of the various reactions have been obtained. The amount of Cu2+ interference in the reaction has also been calculated.
The mechanism of interaction between Cr in CCA preservatives and wood carbohydrates has been clarified. CrIIIand Crvl(as CrO4=) species form soluble generalized complexes with wood carbohydrates. While CrIIIcomplexes have energy that better represent them as a weak adsorption, CrO4=forms proper transition complexes with cellobiose in cellulose or with other disaccharidc units in other wood carbohydrates. Single sugars do not form such complexes but only have a reducing action. Oxidizing and reducing species are identified. In the mechanism proposed, after small initial oxidation, (and possible cleavage) of hemicelluloses and/or cellulose during the initial rapid Crvladsorption and its reduction to CrIII, mixed CrIII,/CrVItransition complexes are formed in which the two Cr species undergo, in turn, reduction and oxidation partially saving the wood carbohydrates from being further oxidized and cleaved. CrIIIis continuously subtracted from the system to form mainly Cr arsenates and other compounds. The energy stability of the various soluble Cr/carbohydrates complexes formed has been calculated and reported.
Electron paramagnetic resonance spectroscopy (EPR) was used to investigate the forms of copper present in Pinus sylvestris treated with several wood preservative formulations. Anisotropic Cu (II) signals, indicative of immobile Cu2+ ions were found for all treated wood samples irrespective of formulation. Correlations of the electronic parameters A(II) and g(II) indicated that copper in the wood treated with amine copper was complexed with 3 or 4 nitrogen atoms from the amine ligands. Formulations containing copper fixed using nitrite ions showed two clearly different copper species in the treated wood. The major form, which was resistant to leaching, had EPR spectral parameters suggesting a complex of the type CuN2O2. In nitrogen free formulations copper appeared to be complexed to 4 oxygen atoms in a distorted octahedral environment. The copper-chromium containing formulations gave a broad Cr (III) signal and a sharp characteristic signal indicating a small quantity of Cr (V) in the treated wood which was stable in wood under dry, laboratory storage but which disappeared after leaching. Overall these studies have demonstrated that the paramagnetic properties of wood samples treated with several Cu (II) based timber preservatives can be readily examined using EPR spectroscopy and indicate that a variety of copper complexes can be formed in preservative treated wood.