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1.
As chromated copper arsenate (CCA) contains copper, chromium and arsenic, waste CCA-treated wood must be separated from other treated wood because of environmental pollution by chromium and arsenic when it is incinerated and the regulation. Therefore, a method to identify CCA-treated wood was developed using laser-induced breakdown spectroscopy (LIBS). Using the LIBS apparatus assembled in our laboratory, plasma on a wood surface was generated by a 4?ns pulse of 1064?nm (55?mJ/mm2) emitted from Nd:YAG laser. Fluorescence from the plasma was collected by an ellipsoidal mirror and analyzed by a spectrometer in the range of 190–300?nm. The results showed that the 228.7?nm line from As and 267.6?nm line from Cr were useful for the identification of CCA-treated wood. As the discrimination capacity was confirmed by the elemental composition analysis by X-ray fluorescence, it was concluded that LIBS can specifically identify CCA-treated wood.  相似文献   

2.
Wood treated with CCB (chromated copper borate) has an expected service life of 20–50 years, depending on conditions of service and method of treatment. After this period, treated wood is discarded as special waste. Due to toxic elements (Cu, Cr, and B) in such treated wood, burning and landfill disposal are not considered as environmentally sound solutions. Chemical extraction seems more promising. The principle of the method is to convert fixed biocides in wood into soluble form and leach them out of the wood. In order to elucidate this process, copper(II) sulfate, potassium dichromate, and CCB-treated samples were leached using five different agents, namely, water, an aqueous solution of oxalic or acetic acid, and an aqueous solution of oxalic or acetic acid with ammonia. Afterwards, the amounts of leached copper and chromium were determined. In a parallel experiment, electron paramagnetic resonance measurements of wet- and dry-leached and unleached samples were performed in order to determine the paramagnetic complexes that were formed. The highest chromium leaching was achieved with the aqueous solution of oxalic acid, as chromium was converted into water-soluble chromium oxalate. While the mixture of oxalic acid and ammonia resulted in the highest copper leaching, EPR observation revealed that in this case water-soluble complexes of copper, oxalic acid, and ammonia were formed. We found out that oxalates formation is not the only mechanism responsible for copper or chromium leaching. High acidity may play an important role too.  相似文献   

3.
Thermal treatment of chromated copper arsenate (CCA) impregnated waste wood is a way to utilize the energy resource of the wood and at the same time to reduce the volume of the waste. An issue of concern in relation to the thermal treatment is As emission to the air. Meanwhile, there is still a matter to cope with when methods to avoid As emission are implemented: the residues with increased concentrations of Cu, Cr and As. In the present paper two different residues after thermal treatment are characterized: a mixed bottom and fly ash from combustion of CCA impregnated wood, and a charcoal from pyrolysis of treated waste wood. By SEM/EDX it was seen that the charcoal still showed wood structure with both tracheids and rays and that Cu, Cr and As were found inside this wood structure. Cu was found alone while Cr and As were often found together. By chemical analysis it was found, too, that the charcoal contained a high concentration of Zn, probably from paint. Chemical extraction experiments in HNO3 were conducted with the charcoal and it was found that the order of extraction (in percentage) was Zn > Cu > As > Cr. A SEM/EDX investigation of the mixed ash from combustion showed the presence of small particles with wood structure with elevated Cu and Cr concentrations, but most particles were irregular shaped matrix particles rich in Si, Al and K. Cr was abundant in many different particles including the lignin skeleton of the small, unburned wood pieces, but also inside silica-based matrix particles. Ca was often found associated with char-like (porous) particles, indicating that Ca-arsenates had been formed during combustion. Cu was often associated with Cr in the unburned wood pieces, whereas it was less abundant inside the silica-based matrix particles. Cu was also found in an almost pure form in a small layer on the surface of some matrix particles indicating condensation of volatile Cu species. Chemical extraction with inorganic acids showed the order of percentages mobilized as: As > Cu > Cr.  相似文献   

4.
Chromated copper arsenate (CCA) is the primary wood preservative used in the United States. CCA products are used for decking, fencing, retaining walls, docks, poles, and highway sign posts. Since CCA became popular in the early 1970's, it is estimated that over 140 million cubic meters of these products are in service. Although the EPA allows disposal of spent CCA products in landfills, increasingly they are looking at the possibility of restricting its disposal. One method for potential re-use of CCA treated wood fiber would be to remove the treatment chemicals and process the fiber into energy or consumer products. The objectives of this research were to determine which method(s) can improve the removal of copper, chromium, and arsenate from spent CCA-treated lumber. The best material, in this research, for leaching chemicals from treated wood with organic acids, were particles (compared to chips and steam exploded wood). Without the functions of organic acids, the best method to remove chemicals proved to be steam explosion and further extraction by water. Citric acid was the most effective acid used in the removal of treatment chemicals of the three acids evaluated: acetic, citric, and sulfuric. The time effect on the extraction process indicated that most of the treatment chemicals were removed within the first seven days of treatment. This study also indicates that steam explosion does not increase the extractability of the chemical components. Other methods need to be examined which may lead to better removal of the chemicals or more effective methods to recycle spent CCA products.  相似文献   

5.
This study evaluated oxalic acid accumulation and bioremediation of chromated copper arsenate (CCA)-treated wood by three brown-rot fungi Fomitopsis palustris, Coniophora puteana, and Laetiporus sulphureus. The fungi were first cultivated in a fermentation broth to accumulate oxalic acid. Bioremediation of CCA-treated wood was then carried out by leaching of heavy metals with oxalic acid over a 10-day fermentation period. Higher amounts of oxalic acid were produced by F. palustris and L. sulphureus compared with C. puteana. After 10-day fermentation, oxalic acid accumulation reached 4.2 g/l and 3.2 g/l for these fungi, respectively. Fomitopsis palustris and L. sulphureus exposed to CCA-treated sawdust for 10 days showed a decrease in arsenic of 100% and 85%, respectively; however, C. puteana remediation removed only 18% arsenic from CCA-treated sawdust. Likewise, chromium removal in F. palustris and L. sulphureus remediation processes was higher than those for C. puteana. This was attributed to low oxalic acid accumulation. These results suggest that F. palustris and L. sulphureus remediation processes can remove inorganic metal compounds via oxalic acid production by increasing the acidity of the substrate and increasing the solubility of the metals.An erratum to this article can be found at  相似文献   

6.
Remediation of copper-based alkaline copper quat (ACQ) and micronized copper quat (MCQ) wood-preservative-treated weathered southern pine mulch samples by monoethanolamine (Mea) extraction was studied. The potential reuse of Mea extract in ACQ wood preservative application was also evaluated. Continuous column extraction of copper-preservative-treated samples for 32 h, using 12 % Mea removed 66–86 % (between top and bottom of the column) and 65–80 % of Cu, respectively, from ACQ- and MCQ-treated wood. Mea extracts of treated wood could be reused in ACQ-treating solutions that met the American Wood Protection Association standard specifications for ACQ wood preservatives. This was achieved either by mixing the extract with industrial Cu–Mea solution at 1:4 ratio or by adding cupric acetate salt directly into the Mea extract. ACQ-treating solutions reformulated using Mea extracts of ACQ- and MCQ-treated wood performed similarly to wood treated with industrial ACQ solution and freshly prepared solution using cupric acetate. All treated wood had similar penetrations of Cu in wood during preservative treatment, Cu leaching from the treated wood in contact with water, corrosion of nails in contact with treated wood, and ability to protect wood from mold growth.  相似文献   

7.
壳聚糖金属配合物处理后竹材的防褐腐作用及力学性能   总被引：1，自引：0，他引：1  
以4年生新伐毛竹为试材,以褐腐菌棉腐卧孔菌为试菌,对壳聚糖铜配合物(CCC)、壳聚糖锌配合物(CZC)及相应的金属盐(氯化锌)和铜铬硼(CCB)、ACQ处理材的耐腐性能、力学性能及胶接性能进行研究.结果表明:1) CCC处理的竹材对棉腐卧孔菌的耐腐性能不及CCB和ACQ处理材;但是,随着CCC处理浓度的增加,处理材耐褐腐性能明显增加,当处理材中金属离子保持量达到5.141 kg·m-3时,腐朽后质量损失低于6.1%.2) CZC处理毛竹试材的耐腐效果低于CCC、CCB和ACQ,略高于氯化锌处理材,当CZC中金属离子保持量高于5.091 kg·m-3时,处理材的质量损失在26.4%～29.0%之间.3) 同素材(未处理材)相比,经防腐剂处理后的竹材力学性能及胶接性能均有不同程度下降,尤其是CCB处理材.在所测指标中,抗弯弹性模量和抗弯强度下降最明显,横纹抗压强度和胶接强度除CCB外变化不大.  相似文献   

8.
The leaching of chromated copper arsenate (CCA) components from unfixed wood immersed in water is modeled in three dimensions using an analytical model of simultaneous diffusion and reaction. Parameters for the model were determined by laboratory leaching experiments with small uncoated wood samples, departing from previous approaches where diffusion coefficients are measured in one dimension at a time. The diffusion coefficients and reaction rate constants of Cr6+, total Cr, Cu, and As in unfixed CCA-treated red pine (Pinus resinosa Ait.) and southern pine (Pinus sp.) were estimated, assuming first-order reaction rate equations and independent Fickian diffusion for all components. Estimated reaction rate constants and diffusion coefficients were not significantly affected by sample dimensions except for very severe longitudinal leaching from short samples. The predictive ability of the model using diffusion coefficients determined from immersion of small lab samples was evaluated by leaching experiments in a spray booth of southern pine lumber at 21 and 60°C, and red pine pole sections at 21°C. The predictive ability of the model was mixed, but in all cases represents a significant improvement over small-block leaching models which do not account for the diffusive nature of the leaching process.  相似文献   

9.
Summary A titration procedure was used to confirm carbon dioxide evolution from wood treated with solutions containing chromic acid and to quantify the effects of species (red pine vs soft maple), solution concentration and reaction temperature on the rate and amount of CO2 evolved. Small blocks or chips were vacuum treated with either chromated copper arsenate (CCA) wood preservative or chromic acid solutions and the release of CO2 monitored until the reaction was complete. Significant volumes of CO2 were measured. This is attributed to the oxidation and subsequent decarboxylation of primary hydroxyl groups on wood constituents. The ratio of moles of CO2 produced to moles of chromium added to the wood ranged from about 0.07 to 0.24 depending on the wood species, solution properties and fixation conditions. This accounted for from 9 to 32% of the total oxidation potential of the hexavalent chromium applied. The relative amounts of CO2 produced were higher for maple than for red pine. The rate of CO2 evolution was also higher in the maple samples, consistent with the higher rate of chromium reduction in soft maple compared to red pine. The amount of C02 produced was approximately proportional to the amount of hexavalent chromium in the CCA treating solution although the ratio of CO2 produced to chromium added to the wood increased slightly with increasing solution concentration. The relative amounts of CO2 produced increased with increasing fixation temperature over the 50–90 °C range in both species. The rate of CO2 evolution was accelerated as the fixation temperature was increased. The rates and amounts of CO2 produced were similar for CCA and Cr03 treatments containing the same concentration of chromic acid. Copper and arsenic components of the CCA solution did not appear to have any effect on the decarboxylation reaction.We gratefully acknowledge the financial support of the Natural Sciences and Engineering Research Council of Canada, Natural Resources Canada;, LPB Poles Inc., Masson Quebec, Timber Specialties Ltd., Campbellville Ontario and Guelph Utility Pole Co. Ltd., Guelph Ont. for this study.  相似文献   

10.
Summary Observations on selective absorption and leaching suggest that the chromium fixes the arsenic preferentially to the copper. Although there appears to be no major amount of fixation of copper by arsenic, at the start of addition of arsenic to copper-chrome formulations there is a small but significant decrease in the leaching of the copper suggesting either a small amount of fixation of copper by arsenic or the formation of an insoluble complex of all three components.Maximum fixation of arsenic was obtained when the Cr/As ratio (as salts) was 1.9 or greater. Maximum fixation of copper is not so simply defined but is round about a Cr/Cu ratio (as salts) of 1.7.The area of maximum effectiveness is not coincident with the area of maximum fixation of both copper and arsenic but slightly displaced towards a region higher copper where there is still maximum fixation of arsenic but some loss of copper.  相似文献   

11.
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. Received: 20 July 2000  相似文献   

12.
Reaction kinetics of fixation of CCA-C (chromated copper arsenate type C) preservative was studied at 30°C in ground wood of trembling aspen, red pine, and red maple at treatment retentions of 4.0, 6.4, 9.6, and 30 kg/m3, and red maple pre-extracted with hot water at retentions of 6.4 and 30 kg/m3. Reaction orders of cumulative Cr, Cu, and As reactions decreased gradually during the fixation if calculated by Van’t Hoff’s method. With Essen’s method, CCA fixation was best approximated as follows: Cr—3rd order reaction during the first 24 h, and 1st order reaction for the rest of the fixation period; Cu—2nd order reaction; and As—1st order reaction in red pine and aspen, and 2nd order in red maple. Rates of reaction decreased with increased CCA solution concentration for Cr and Cu, and increased for As, except in red maple. Reaction rates for all CCA elements were significantly higher in rapidly fixing red maple than in regularly fixing red pine and aspen, and were higher in unextracted than pre-extracted red maple. Modeling of CCA fixation kinetic for the whole fixation period enabled comparison of fixation reactions among wood species, preservative components, and treatment retentions.  相似文献   

13.
Summary Electronmicroscope microanalyser (EMMA-4) analysis of Poria monticola colonising pine wood treated with a copper-chrome-arsenate preservative has shown that the fungus removes copper chromium and arsenic from the wood and stores these elements within the hyphae to the extent of 3–4% on a mycelial dry weight basis. The total uptake of each element varies from spot to spot examined (each 0.2 m dia.) but is on an average correlated with the concentration of the element in the impregnated wood. It appears that the rate of copper uptake is higher than of arsenic uptake.  相似文献   

14.
Abstract

One of the main objectives of thermal modification is to increase the biological durability of wood. In this study the fungal resistance of Norway spruce and Scots pine, thermally modified at 195°C and 210°C, was studied with a lap-joint field test. Untreated pine and spruce and pine impregnated with tributyl tin oxide (TBTO) and copper, chromium and arsenic (CCA) were selected as reference materials. The evaluations were carried out after 1, 2 and 9 years of exposure. After 1 and 2 years of exposure mainly discoloration was detected. Only the untreated pine was slightly affected by decay fungi. There were significant differences in the decay ratings of untreated and thermally modified wood materials after 9 years in the field. While the untreated wood materials were severely attacked by decay fungi or reached failure rating, only small areas of incipient decay were detected in the thermally modified samples. Thermally modified pine was slightly more decayed than thermally modified spruce. The only wood material without any signs of decay was CCA-treated pine, since some of the TBTO-treated pine samples were also moderately attacked by fungal decay. The results of the lap-joint test had a good correlation with mass losses in a laboratory test with brown-rot fungi.  相似文献   

15.
Copper and arsenic K-edge X-ray absorption fine structure spectroscopy (EXAFS) of pine wood (Pinus radiata) treated with chromated copper arsenate (CCA) timber preservative have been measured. Refinement of the data is consistent with arsenate anions bound to chromium and copper ions isolated from other heavy elements, regardless of depth into the wood. This constitutes the first substantive analysis of CCA's fixation products and has a number of implications for models of fixation.  相似文献   

16.
Summary A preliminary study of a wide range of copper-chrome-arsenic formulations indicates that the most offective are in the region, CuSO4·5H2O-35 to 45 per cent; K2Cr2O7-40 per cent and above; As2O5·2H2O-25 to 15 per cent or less. Effectiveness appears to depend more on the copper content than the copper-arsenic. Observations on selective absorption and leaching suggest that the chromium fixes the arsenic preferentially to the copper. Although there appears to be no major amount of fixation of copper by arsenic, at the start of addition of arsenic to copper-chrome formulations there is a small but significant decrease in the leaching of the copper suggesting either a small amount of fixation of copper by arsenic or the formation of an insoluble complex of all three components.Maximum fixation of arsenic was obtained when the Cr/As ratio (as salts) was 1.9 or greater. Maximum fixation of copper is not so simply defined but is round about a Cr/Cu ratio (as salts) of 1.7.The area of maximum effectiveness is not coincident with the area of maximum fixation of both copper and arsenic but slightly displaced towards a region of higher copper where there is still maximum fixation of arsenic but some loss of copper.  相似文献   

17.
Summary The study was carried out in order to determine the effects of CCA on the pyrolysis and the combustion toxicity of wood. The results from CCA treated wood are summarized as follows: 1. CCA accelerated the beginning of pyrolysis of wood, increased the activation energies for the weight loss by pyrolysis, and increased the char yields in both air and helium. 2. Almost all the original amounts of cromium and copper were retained in the ash while some of the arsenic evolved into the gas phase, which increased with increasing temperature and air supply. 3. The combustion toxicity of wood samples was affected more by the sample density and CO concentration than CCA. It is concluded that for minimizing gaseous toxicants from arsenic, CCA treated wood must be burned at low temperatures with a reduced air supply.  相似文献   

18.
Abstract

Mercury intrusion porosimetry (MIP) was used to evaluate the impregnation mechanisms of wood by methyl methacrylate (MMA) through examining the changes in porosity, pore volume, pore size distribution and bulk density of solid wood before and after MMA impregnation. Porosities of MMA-impregnated (hardened) wood samples were lower than those of solid wood samples for six studied species, five hardwoods and one softwood. Densities of hardened wood were enhanced from 45 to 130% depending on the species. The pore volume available for mercury intrusion was shifted from pore d>0.1 µm for solid wood to pore d≤0.1 µm for hardened wood. A pore diameter of 0.1 µm was used as the transition point for MMA impregnation and the increased mercury penetration below this point was attributed to the MMA polymer pore structure. Porosity as an intrinsic property of wood appears to be the main determinant of impregnation rate and polymer retention, especially for porosity with pore diameter >0.1 µm. The results indicate that the MIP technique is an effective tool with which to study the impregnation process.  相似文献   

19.
以4年生新伐毛竹为试材,以白腐菌彩绒革盖菌为试菌,对壳聚糖铜配合物(CCC)、壳聚糖锌配合物(CZC)及相应的金属盐(氯化锌)和铜铬硼(CCB)处理材的抗流失性和耐腐性能进行试验.结果表明: 壳聚糖金属配合物在竹材中固着率略高于CCB,明显高于相应的金属盐,具有较强的抗流失性能;CCC处理的竹材对彩绒革盖菌的耐腐性能高于CCB处理材, 当CCC处理材中金属离子保持量达到6.35 kg·m-3时,腐朽后质量损失为0;CZC处理毛竹试材的耐腐效果和CCC效果相当,明显高于氯化锌处理材,当防腐剂中金属离子保持量高于2.41 kg·m-3时,CZC处理的竹材都达到最耐腐等级,且随着防腐剂中金属离子保持量的提高,处理材的质量损失率接近于0.  相似文献   

20.
The unidirectional leaching of unfixed hexavalent chromium (Cr6+) from wood freshly treated with chromated copper arsenate (CCA) is modeled as simultaneous diffusion and first-order chemical fixation reaction. Small wood specimens were coated to restrict preservative movement to one direction, then treated with CCA and immersed in water to evaluate unidirectional leaching characteristics. The directional diffusion coefficients and reaction rate constants of Cr6+ in unfixed CCA-treated red pine (Pinus resinosa Ait.) and southern pine (Pinus sp.) were estimated by least squares fitting of the model to leaching results in each direction independently. The reaction rate constants calculated from the diffusion and leaching model were generally consistent with results from pure fixation experiments, although the computed rate constants increased under the most severe longitudinal leaching conditions. The applicability of using diffusion coefficients and rate constants estimated from leaching results was tested using a finite difference implementation of the diffusion and reaction model to predict unidirectional leaching from small samples immersed intermittently in water. The predicted leachate quantities were consistent with experimental measurements at the end of each of five leaching events of various durations at temperatures alternating between 13 and 23°C over a 9-day period.  相似文献   

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