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Effects of sodium hypochlorite on compression strength and copper retention of spruce wood treated with copper azole and alkaline copper quat
2007 - IRG/WP 07-40362
This work investigates the effects of sodium hypochlorite on compression strength values and copper retention ratios of refractory spruce wood (Picea oriental L.) treated with the waterborne preservative Copper Azole, (CBA-A, Tanalith-E 3492) and alkaline copper quat (ACQ-2200). Before the copper azole and alkaline copper quat treatment, the samples were immersed in 500 ml of sodium hypochlorite solution for three different durations (2, 4, and 6 hours). A 2 % active ingredient solutions of CBA-A and ACQ were applied for use in vacuum treatment of the sapwood samples. Average copper contents of the specimens were higher than that of the control groups except of the 6-hours sodium hypochlorite treatment in ACQ impregnation. The highest copper value was seen in the variation the 6-hours sodium hypochlorite treatment in the CBA-A impregnation. Compression strength values generally slightly reduced compared to the control groups especially in ACQ impregnation.
S Yildiz, E Dizman, A Temiz, Ü C Yildiz


Micro-Distribution of Micronized Copper in Southern Pine
2008 - IRG/WP 08-30479
For copper-based preservatives to be used in ground contact, penetration of copper into the cell wall is believed to be important to protect the wood from soft rot fungi. Preservatives containing soluble copper are known to do this. It is not known whether preservatives containing particulate copper will also migrate into the cell wall in sufficient quantities to control soft rot decay. An AWPA standard E11 leaching test found that leachate from southern pine blocks treated with a preservative containing particulate copper (Micronized copper quat) contained copper ions, suggesting that copper-containing particles in the treated wood slowly release mobile copper. Southern pine sapwood samples treated with wood preservatives containing soluble (ACQ-D) and particulate copper (Micronized copper quat), as well as untreated southern pine sapwood, were analyzed by Environmental Scanning Electron Microscopy (ESEM) and Energy Dispersive X-Ray Spectrometry (EDS). Copper was detected in the lumens of wood treated with both preservatives, and not in the untreated control. Moreover, the presence of small amounts of copper in the cell walls of samples treated with Micronized copper quat and ACQ-D was indicated by ESEM and EDS. This was further supported by the results of a fungal cellar test and a field stake test which demonstrated that wood treated with Micronized copper quat is resistant to soft rot attack. Future work will investigate copper mobility from particles lodged in the lumens.
R Stirling, J Drummond, Jun Zhang, R J Ziobro


Comparison of laboratory and natural exposure leaching of copper from wood treated with three wood preservatives
2008 - IRG/WP 08-50258
Standard and non-standard laboratory and field leaching tests were used to compare copper leaching from wood treated to above ground and ground contact specified retentions for three wood preservative systems, CCA-C, ACQ-D and a micronized copper formulation with quat DDAC as co-biocide. Copper leaching was highest for the ACQ formulation. Percent leaching was lowest for the micronized copper system (MCQ) but amount of copper leached (mg/m2) was higher for MCQ than for CCA because of the higher copper content in the former formulation. The amounts of copper leaching varied considerably from test to test, but in most cases, the relative amounts of copper leaching from wood treated with the three formulations were consistent. One exception was the AWPA E20 soil leaching test which provided variable results, that showed that leaching of copper from CCA and MCQ samples was more similar to that from ACQ samples than observed for the other test methods. Also, the natural exposure tests (horizontal and vertical exposure) has less dramatic differences among the preservative systems.
P A Cooper, Y T Ung


Copper to quat ratio in alkaline copper quat (ACQ) wood preservative - Effects on fixation and leaching of preservative components in red pine
2009 - IRG/WP 09-30496
This study investigates the effect of the relative proportion of copper oxide (CuO) to didecy dimethyl ammonium carbonate (DDACb) in an alkaline copper quat (ACQ) formulation on the rate of copper fixation or stabilization and the resistance of treated wood to leaching of copper and quat (DDACb). Red pine samples were treated with ACQ, having CuO to DDACb ratios of 2:1 (the normal ratio for ACQ-D), 1:1 and 1:2, at concentrations of 0.6%, 1% and 1.5%. Treated samples were wrapped in plastic and post treated at 500C. Samples were squeezed to express solution, which was analyzed for copper to measure the percentage copper fixed at different times during post treatment conditioning. Conditioned samples were subjected to AWPA E11 laboratory leaching experiments and the amounts of copper and DDACb leached from the samples were analyzed. A decrease in relative proportion of copper in the ACQ formulation from a CuO to DDACb ratio of 2:1 to 1:1 and 1:2 resulted in a substantial reduction in the time required for the fixation of copper. There was a significant decrease in the amount of copper leached from the species studied with reduction of relative proportion of copper in the ACQ formulation. The reduction in leaching was higher for samples treated with concentrations of 1% and 1.5% ACQ compared to the sample treated with 0.6% ACQ. Formulation having 1:1 CuO to DDAC ratio appears to be the most promising, considering the positive effects of reduced copper ratio on copper leaching and fixation time and the minimal effect on DDAC leaching.
S Pankras, P A Cooper, T Ung, L Awoyemi


Re-Distribution of Copper in the Cell Walls of Wood Treated with Micronized Copper Quat
2009 - IRG/WP 09-30506
Wood treated with copper-based preservatives to be used in ground contact may fail to inhibit soft rot fungi if penetration of copper into the cell wall is insufficient. Preservatives containing soluble copper are known to penetrate the cell wall; however, it is not known whether preservatives containing particulate copper will also migrate into the cell wall in sufficient quantities to control soft rot decay. A method was developed to accelerate and detect re-distribution of copper into the cell wall. Copper was found to re-distribute into the cell wall, presumably from cell lumen deposits, in both ACQ- and micronized copper quat-treated samples after exposure to high temperature and relative humidity. In a non-accelerated test, copper was not found to re-distribute into the cell wall in either ACQ- or micronized copper quat-treated samples after exposure in soil at 15°C for eight weeks.
R Stirling, J Drummond


Evaluation of ACQ-D treated Chinese fir and Mongolian Scots pine with different post-treatments after 20 months of exposure
2010 - IRG/WP 10-30530
The performance of alkaline copper quat-type D (ACQ-D) treated Chinese fir (Cunninghamia lanceolata Hook.) and Mongolian Scots pine (Pinus sylvestris Linn. var. mongolica Litv.) stakes after 20 months exposure in Chengdu and Guangzhou of southern China were evaluated according to AWPA standard E07-07. The ACQ-D treatments used two concentration levels (0.5 and 1.0%) and four different post-treatments (air drying for 1 month, conditioning at 70°C, 80% R.H. for 24h, oven drying at 110°C for 24h, boiling in water for 15h), respectively. The field test results showed that the natural durability of Chinese fir is a little better than Mongolian Scots pine but the untreated sapwood stakes of both wood species were mostly destroyed after 20 months exposure. After ACQ-D treatment, the sapwood of both wood species showed much better biological performance. Among the four post-treatments, the oven drying method (OD) rated the worst by showing slight reduction in biological performance and the most obvious reduction in compression strength after exposure, while the other three post-treatments performed similarly. It suggested that both post-treatments of HC (conditioning in humidity chamber) and HW (hot water bath) could be good selections for accelerating copper fixation in ACQ-D treated wood. And also, Chinese fir from plantation forests could be a potential wood species for preservation.
Lili Yu, Jinzhen Cao, Wei Gao, Haitao Su


Combined effects of thermal modification and ACQ-D impregnation on properties of southern yellow pine wood
2013 - IRG/WP 13-40637
In this study, samples of southern yellow pine sapwood were first thermally modified and then treated by the alkaline copper quat-type D (ACQ-D) wood preservative. Two heating temperature (180℃ and 220℃) and two concentrations of ACQ-D solution (0.9% and 1.35%) were used in the experiments. The combined effects of thermal modification and ACQ-D on leaching performance, mechanical properties and mold resistance of the treated wood were then investigated. The results of the experiments indicated that thermal modification increased the percentage of copper leaching and decreased the MOR and MOE of wood, and also it affected the compression strength parallel to grain. After the ACQ-D impregnation, the bending properties of thermally modified wood got lowered to some extent. The anti-mold experiment indicated that the ACQ-D impregnation could improve the mold resistance of thermally modified wood.
Wang Wang, Yuan Zhu, Jinzhen Cao


Effect of exposure site on metal migration from copper azole, alkaline copper quat or chromated copper arsenate treated southern pine decking
2015 - IRG/WP 15-50313
Metal migration from chromated copper arsenate, copper azole or alkaline copper quaternary compound treated southern pine lumber was assessed at sites in Mississippi and Oregon. Metal levels tended to be consistently higher in decks exposed in Mississippi. Rainfall characteristics did differ slightly at the two sites, but the levels did not appear to be of a magnitude that might affect metal mobility. The results suggest that tests of methods for limiting preservative migration from treated wood must expose materials at multiple sites to ensure that the processes are broadly appropriate.
J J Morrell, H M Barnes


Overview of the treated wood quality control program in the United States with the recent challenges and advances
2017 - IRG/WP 17-20616
In the past two decades, there have been significant and rapid changes in wood protection technologies for residential applications which have moved away from long established heavy duty metal oxide based products such as chromated copper arsenate (CCA). The successor generation of wood protection systems usually contain copper as the primary biocide, in combination with carbon-based co-biocides such as quaternary ammonium compounds (Quat), and/or triazoles (Tebuconazole and/or Propiconazole). The most recent developments have given rise to even more complicated combinations including multiple carbon-based biocides formulated in the form of emulsions or dispersions with or without water repellents or polymers aiming to minimize the use of heavy metals as well as provide improvement in wood dimensional stability and surface weathering performance. Also, long developed non-biocidal wood modification treatments, such as acetylation, thermal modification, furfurylation and hydrocarbon wax/oil treated wood have finally gained more commercial traction in the market place, especially in Europe. These new developments have challenged the industry to develop and use appropriate methods in order to meet the quality control (QC) standards and requirements in respect to concentration of treatment solutions, as well as chemical retention and penetration in treated wood. In the US, the QC system for treated wood product includes three key elements: treating plant internal QC for treating solution, treated wood, and treatment process; QC assistance and monitoring by the chemical/technological suppliers for their customers, and QC inspection by third-party inspection agencies. The enforcement of the QC standards through this comprehensive system is essential to ensure the performance of the treated wood products, the validity of product warranty program, and ultimately for the protection of consumers and the public. This paper overviews the US’s current QC standards and procedures used by treating plants, suppliers and independent inspection agencies. The chemistry challenges with the recent developments of multi-component systems and complex wood protection technologies, and their impacts on quality control methods are also discussed. Case studies have been used to illustrate how some of these challenges can and have been successfully addressed.
L Jin


The Effect of Heat on the Retention of Ammoniacal Copper Quat (ACQ-AB) onto Scots Pine (Pinus Sylvestris L.) Wood
2008 - IRG/WP 08-40390
In this study, the sapwood of Scots pine (Pinus sylvestris L.) were treated with ammonical copper quat type (ACQ-AB), which is one of the environmentally friendly wood preservatives, by using soaking method as a functions of various temperatures and time. The results indicated that the retention behaviour of ACQ onto the wood was considerably affected by temperature of ACQ solution and treatment time.
M Hakki Alma, A Mukremin Kara


A study of decay type variability in variously treated Fagus sylvatica and Pinus radiata field test stakes exposed at a vineyard for 30 - 45 months
1998 - IRG/WP 98-10271
Pinus radiata test stakes were treated with 10 kg/m3 of CCA plus 4 lower retentions in a geometric series of 1.5. Fagus sylvatica was treated with 15 kg/m3 and 2 lower retentions. Both timber species were also treated with equivalent retentions of various new generation preservatives (P. radiata was also treated with creosote). Whilst these stakes were exposed at 11 sites in New Zealand (NZ) and 2 in Queensland Australia, this paper reports only data from a single NZ site where preservative and timber species effects on decay type were particularly pronounced. Of particular interest was the finding that copper-azole and copper-quat. treated pine was less susceptible to soft rot attack but more susceptible to attack from tunnelling bacteria, compared to CCA treated wood. Beech was not attacked by tunnelling bacteria but was attacked by an unusual type of fungal cavitation/erosion. These, and other preservative and timber species effects on decay type are discussed.
R N Wakeling, A P Singh


Working plan: Second international collaborative field trial
1995 - IRG/WP 95-20056
This paper describes the scope, objectives, and approaches to be used in the second international collaborative field trial approved by the Scientific Programme Committee for partial funding in 1994. The trial is designed to develop a broad data base on causal mechanisms, interactions, and factor affecting the performance of treated wood in ground contact. The trial encompasses 12 different field test sites representing all continents except Antarctica. Preservatives were chosen to represent new technologies and include oilborne, waterborne copper-organic, and water-dispersible systems. CCA is used as the reference system. Task forces to research the following areas are described: accelerated soilbed testing, decay types/modes of failure, preservative depletion, abiotic factors, and copper tolerance.
H M Barnes, T L Amburgey


The effect of additives on copper losses from alkaline copper treated wood
2007 - IRG/WP 07-50246
The replacement of chromated copper arsenate (CCA) by alkaline copper compounds has heightened awareness of the potential impact of copper losses on aquatic organisms. While there remains a healthy debate concerning the actual risk of copper leaching from wood preservatives into aquatic ecosystems, it is clear that reducing these losses will be necessary to avoid continued regulatory actions against the use of preservatives in these environments. While post-treatment processing and coatings can reduce losses, neither is completely effective. Another alternative is to add compounds to the alkaline system to complex or otherwise reduce copper losses, much in the same way that chromium acts in CCA. One possible additive is Di(hydrogenated tallowalkyl) dimethyl ammonium chloride, also know as 2HT, which is a common fabric softener. Preliminary tests suggested that this compound reduced copper losses from alkline copper quat and, in doing so, improved overall biological performance. In this report, we describe additional trials to assess the effect of 2HT on copper migration from wood treated with either ACQ or copper azole (CA). 2HT had a variable effect on copper migration, but was associated with reduced copper losses in some treatment combinations. Further trials are underway to assess the biological efficacy of wood treated with combinations of 2HT and either ACQ or CA.
J Mitsuhashi, J J Morrell, L Jin, A F Preston


Biological efficacy of micronized copper systems
2008 - IRG/WP 08-30485
Soil block, fungal cellar and field stake test data will be presented for micronized copper systems. The copper portion of the formulations is present as a fine dispersion of "micro" particulates while the co-biocide is present as either a soluble quat or an azole containing emulsion. This testing generally used the amine based counterpart as the control preservative system and the micronized formulations perform as well or better than the amine formulations. In 5 year field stake tests in Gainesville, FL, the micronized copper quaternary formulation significantly outperformed the amine copper quaternary formulations. Strength and fixation testing is also discussed.
C R McIntyre, M H Freeman


Alkaline copper treated wood for use in residential decking
2008 - IRG/WP 08-30490
Alkaline copper quaternary ammonium compound (ACQ) treated decking was exposed in a field experiment and the mobile copper assessed based on that collected in the leachate. The amount of copper which leached was modeled after 4 years. The results showed that boards which leached most chemical initially provided the greatest loss over four years. The reduction in the mobility of copper with time was calculated and found to approach zero after about 11 years. The application of water repellant slowed down the loss of copper and could extend the mobile copper duration beyond that in control samples. The migration of copper onto check surfaces was confirmed with retentions exceeding that reported to protect wood above ground from spore germination by basidiomycete fungi.
J N R Ruddick


Corrosion of fastener and connector in contact with alkaline copper treated wood – it is a problem
2008 - IRG/WP 08-40437
For many decades, chromated copper arsenate (CCA) was the most common wood preservative used in North America for residential and industrial applications. Since December 31, 2003, the use of CCA for residential application was voluntarily terminated. One of the most widely accepted alternative wood preservatives in Western Canada is Alkaline Copper Quaternary Compound (ACQ). This paper will compare the corrosion data of CCA-treated wood with that of ACQ treated wood at a similar preservative retention. It also discusses the appropriate methodology for carrying out the corrosion studies. A modified draft American Wood Protection Association (AWPA) corrosion test method was used, where fasteners were sandwiched between two pieces of treated wood and exposed to the continuous water mist at an elevated temperature. All fasteners were tested for resistance of the coating to mechanical damage, prior to exposure. The study demonstrated that ACQ treated wood is indeed more corrosive than CCA treated wood. The study also showed that the application of water repellant to ACQ treated wood significantly reduced the corrosion rate. The best estimation of the corrosion rate was the measurement of the loss in the average core diameter in combination with a visual evaluation of the fastener and corrosion products.
J N R Ruddick


Leaching of the copper component from full scale decking boards during one summer season
2009 - IRG/WP 09-50260
The leaching of copper has been tested in laboratory and in outside exposure for freshly treated pine sapwood samples with three different copper preservatives, Cu HDO, copper quat and copper triazoles. We found in the laboratory leaching test that a fixation with warming to 60 °C (140 °F) for 48 hours without drying and then drying in the laboratory in room temperature gave the lowest leaching of copper. We also found that surface treatments with wood oils reduced the leaching, and that washing of the surface before testing had no effect. Full scale decking board samples (0.25 m2) were then exposed outdoors for rain. The rain water was collected and analysed for copper. After one summer season (about 600 mm rain) we found that the leaching differ for the three preservatives. All samples with a water borne surface treatment had the lowest leaching, about half the amount of untreated.
F G Evans


Component leaching from CCA, ACQ and a micronized copper quat (MCQ) system as affected by leaching protocol
2009 - IRG/WP 09-50261
Leaching results for Cu, Cr and As (CCA) and Cu (ACQ and MCQ) from southern pine are compared for laboratory tests (AWPA E11, and draft OECD methods I and II) and natural weathering of horizontally and vertically oriented lumber samples over two seasons. This paper expands on results and comparison of results presented at the IRG regional meeting in Costa Rica in Dec 2008 (Cooper and Ung 2008) and provides direct comparisons among leaching results for various laboratory and natural weathering conditions. It includes leaching of As and Cr components of CCA and estimates of cumulative DDACb leaching from ACQ and MCQ samples exposed to natural weathering.
P A Cooper, Y T Ung


Adsorption of ACQ components in wood
2010 - IRG/WP 10-30522
To investigate the chemical adsorption capacity of copper-monoethanolamine (Cu-Mea) components on wood, the Na+ cation exchange capacity (CEC) of red pine (Pinus resinosa Ait.) was determined and compared to the adsorption capacity of free Mea and Cu-Mea complexes. The CEC increased with increasing pH. Free Mea adsorption as a function of pH followed the sodium adsorption curve except at pH over 9, when it exceeded the CEC. Cu-Mea adsorbed up to the CEC at pH 9.0-9.5 apparently as Cu(Mea)+, whereas the complex in solution is predominantly of the form Cu(Mea)2+. For the quaternary ammonium compound, alkyl dimethyl benzyl ammonium chloride (ADBAC) adsorption isotherm showed two different adsorption mechanisms into wood: ion exchange reaction at low concentration and hydrophobic interaction at high concentration. ADBAC adsorbed at solution concentrations below a critical concentration (hemi-micelle concentration) had high leaching resistance while ADBAC adsorbed into wood at above the critical micelle concentration (CMC) had low leaching resistance. The CMC decreased with addition of Mea and Cu-Mea. The anion, Cl- of ADBAC was only adsorbed at solution concentrations above the CMC and was easily leached out. The adsorption capacity of ADBAC into wood by cation exchange reaction did not achieve the cation exchange capacity (CEC) of wood. However, the total adsorption of ADBAC and Cu achieve the CEC of wood in the presence of copper amine, and ADBAC competes with copper to occupy the same sites in wood.
Myung Jae Lee, P Cooper


A comparison of the chemistry of alkaline copper and micronized copper treated wood
2010 - IRG/WP 10-30528
This paper discusses the chemistry of the reaction of alkaline copper and micronized copper with wood. The objective of this study is to examine the copper species produced in wood during the fixation reaction using electron paramagnetic resonance (EPR) spectroscopy. The initial experiments (phases 1 to 2) were designed to confirm the effect of time of treatment and solution concentration on the spectral parameters of copper in sawdust treated with copper sulphate solutions. The relative ease of distinguishing the copper produced from alkaline copper treatments with those produced during treatment of aqueous copper solutions was the focus of phase 3 while phase 4 examined the chemistry of sawdust treated with aqueous suspensions of copper carbonate. In the final phase, the focus was on determining whether a soluble copper species could be identified in wood treated with micronized copper preservatives. The spectra were compared to those of sawdust treated with aqueous suspensions of basic copper carbonate. The results of the study clearly show that soluble copper is produced relatively rapidly in wood treated with aqueous suspensions of basic copper carbonate and that this copper reacts with wood to produce similar copper complexes to that formed between wood and copper sulphate. These copper complexes resist leaching. This would support the premise that soluble copper formed by the reaction between basic copper carbonate and wood, can migrate into the wood cell wall in a manner similar to other soluble copper chemicals, and bind to wood cell components. Further research is in progress to further identify the chemistry of these reactions.
Wei Xue, P Kennepohl, J N R Ruddick


A Comparison of the Performance of Related Copper Based Preservatives against Soft Rot
2010 - IRG/WP 10-30540
The performance of pine and beech wood treated with either a soluble copper + quat (ACQ type D) preservative system or a particulate copper + quat system was evaluated in unsterile soil using the European standard ENV 807 soft rot decay test procedure. In addition, to compare soft rot performance of soluble and particulate copper directly without the influence of co-biocides, beech and pine test blocks were treated with either a soluble copper formulation or particulate copper system to equivalent copper retentions and then exposed to mixed cultures of soft rot fungi in a vermiculite medium according to ENV 807 Annex A. Relative performance of the different formulations was determined using weight loss data.
M Ray, D Dickinson, K Archer


A comparison of the corrosion of alkaline copper and micronized copper treated wood
2010 - IRG/WP 10-40515
With the replacement of chromate copper arsenate (CCA) by alkaline copper wood preservatives, there have been reports of increasing corrosion of metal fasteners and connectors in contact with treated wood. This may be explained by the presence of more mobile copper in the treated wood. One novel industrial response has been to develop a wood preservative based on an aqueous solution containing suspended basic copper carbonate and a co-biocide. This micronized copper preservative relies on the basic acidity of wood to release the copper which can complex with the wood components. As a consequence of the lower amount of mobile copper, the degree of corrosion should be significantly lowered, compared to the corresponding alkaline copper preservatives. The objective of this study is to examine the relative corrosiveness of micronized copper and alkaline copper treated wood to determine whether a significant reduction in corrosiveness is obtained. The interim results of the study have confirmed a significant reduction in the degree of corrosion on hot dipped galvanized fasteners as well as a lower rate of corrosion on bright (or common iron) fasteners. The levels of the corrosion of the micronized copper treated wood were similar to those observed for western red cedar, a durable wood that has been used in the past for decks and fences in British Columbia.
M Kofoed, J N R Ruddick


Copper distribution in soil leached from full scale decking boards during one year
2010 - IRG/WP 10-50265
The distribution of copper in the soil under exposed decking boards after one year has been analysed. The decking boards were impregnated with copper HDO, copper quat and copper triazoles. The decking boards were pine sapwood and pressure treated in a full cell process, fixed by heating and then dried. The samples were not surface treated. Each decking sample of five boards (0.25 m2) was placed on a frame of untreated spruce, 10 cm above the soil surface. In addition to the three treated samples, there was one untreated as a reference. After one year of exposure, the samples were removed and soil samples in different depths were taken. These were later boiled in de-ionised water and nitric acid (pH=2). The solutions were analysed for copper. Only the surface samples (0-2 cm) had elevated copper content compared to the back ground level. The copper fixes hard to the soil and only small amounts of copper will be washed out by rain.
F G Evans


Mold Control for Treated Lumber in Block-Stack Storage Conditions
2012 - IRG/WP 12-30588
The mold development and control for freshly treated and block-stacked wood have been evaluated using a green house mold testing method. The results for the mold resistance of several commonly used water boron preservative treatment systems, such as ACQ, Copper Azole, and borates with and without inclusion of mold inhibitors are presented. The data suggest that the different preservative treatment systems have their own very different mold resistance characteristics. The addition of mold inhibitor or in some cases combination of mold inhibitors or additives can provide effective control of mold development. The results also suggest that the green house mold test method reported here can simulate the worst case scenario confronted by treated wood in block-stack situations during storage, retailing and installation.
L Jin, P Walcheski, A Preston


Removal of nano- and micronized-copper from treated wood by chelating agents
2013 - IRG/WP 13-50294
Micronized and nano-copper (Cu)-based and arsenic and chromium-free systems have received much attention for wood protection in recent years. Because they have different fixation, and micro-distribution properties, such copper systems may be more or less subject to release using known remediation methods than soluble forms of Cu. This study evaluated Cu recovery from wood treated with micronized- or nano-Cu via chemical extraction, and determined optimum release rates of Cu from micronized- and nano-Cu-treated wood compared with the release rates from soluble Cu-based wood preservatives. Chemical remediation in the study included chelating agents EDTA, oxalic acid, bioxalate, and D-gluconic acid at different durations, pH, and concentration levels to remove Cu from treated wood along with distilled water as controls. Cu removal rates increased from around 60% to over 95% when bioxalate was employed in the extraction process for all extraction durations. In extractions of nano CuO-treated wood for 24h, oxalic acid was able to remove 95% of Cu; however, bioxalate was able to remove somewhat less Cu. Bioxalate was, on the other hand, more effective than oxalic acid in removing Cu from ACQ-D, MCQ, MCA, CA-C and Cu-Et-treated wood. D-gluconic acid extractions resulted in the lowest Cu removal rate for nano-CuO. As the pH of D-gluconic acid was reduced from 10 to 2, the percentage Cu removal considerably was improved except for nano CuO. Results suggested that there is no distinctive difference in Cu removal rates among ACQ-D/MCQ, CA-C/MCA and Cu-Et wood preservatives. Nano-CuO was found to be resistant against EDTA extractions. Since it is a weak, noncorrosive, nonvolatile, nontoxic, biodegradable and inexpensive organic acid, D-gluconic acid can be used as an alternative to commercial EDTA and bioxalate in chemical remediation of Cu-treated waste wood.
S N Kartal, E Terzi, B Woodward, C A Clausen, S T Lebow


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