Hydrothermal Treatment of Creosote-Impregnated Wood

This paper describes the treatment of creosote-treated wood in anoxic supercritical water (SC). Decommissioned (ca. 15 yr) creosote-treated pine utility pole wood, which had been chipped was hydro-treated directly. During treatment, the creosote-derived hydrocarbon residues in the wood were nearly completely (>99%) recovered, and the wood itself was transformed into a mixture of hydrocarbons including substituted benzenes, phenolics, and light PAHs. These wood-derived transformation products served to reconstitute the "light end" of the creosote, which had been largely lost while in service. Thus, the hazardous waste (creosote hydrocarbon mixture) was recovered, and the solid waste (wood) was transformed into a complementary product mixture in a single pass. Solid residues after 12-20 h of treatment wer

Biotransformation of Tebuconazole by Microorganisms: Evidence of a Common Mechanism

A major problem with organic wood preservatives is biotransformation by both wood decaying and wood-inhabiting but nondecaying microorganisms in long-term service. Detoxification of organic biocides may contribute significantly to treated wood failure. In this study, a bacterium (Pseudomonas fluorescens), mold (Trichoderma harzianum), soft rot (Chaetomium globosum), white rot (Phanerochaete chrysosporium), and brown rot (Meruliporia. incrassata) were used to access the extent of biotransformation and the initial metabolite products of tebuconazole in liquid cultures. This study proposed metabolic pathway(s) and explored the possibility of a common biotransformation mechanism for all species. P. chrysosporium showed little ability to metabolize tebuconazole. Within 21 da, 40.4, 59.9, 68.2, and 70.2% tebuconazole was metabolized by M. incrassata, C. globosum, T. harzianum, and P. fluorescens, respectively, into a form that may be less toxic. Mass spectroscopy and infrared analysis of isolated metabolites indicated that the major pathway was cleavage of the triazole ring on tebuconazole and that most species mainly performed oxidation reactions to form the alcohol monolog, which was further oxidized to form the carboxylic acid analog of tebuconazole. Only T. harzianum metabolized the hydroxyl group on the tert-butyl moiety by acetylation to form an ester

Effect of Steaming and Hot-Water Soaking on Extractive Distribution and Moisture Diffusivity in Southern Pine During Drying

Samples of southern pine sapwood and heartwood were treated five different ways: steaming in the saturated condition for 1 h and 5 h, respectively, steaming at a moisture content near the fiber saturation point (FSP) for 1 h, hot-water soaking for 10 h, and steaming near 95% relative humidity at an equilibrium moisture content (EMC) slightly below the FSP for 1 h at 100°C. The samples were dried from near saturation condition to an EMC slightly below the FSP, and then to final 12% EMC. The results indicate that the amount of extractives removed tended to be evenly distributed along the flow direction before drying and after drying to near FSP, which suggests that extractives move with water in wood in response to moisture gradient during drying. Hot-water soaking and prolonged steaming increased the moisture diffusivities above and below the FSP. The variation in diffusion coefficient was partially due to changes in the extractive distribution profile

Removal of Creosote from Wood Particles at Different Horizontal and Vertical Locations of Decommissioned Poles Using Steam Treatment

This study used steam treatment to evaluate the potential of this method to remove residual creosote content of sawdust from weathered, out-of-service poles. Steaming was successful in reducing the creosote content to a level of 1.31%, regardless of creosote content at the start of the steaming treatment. Poles with higher initial creosote contents required longer steaming durations. At any given initial preservative content, creosote removal from weathered poles was more difficult than from freshly treated poles. Moreover, creosote from samples taken near the inner core of the poles was also more difficult to remove than creosote in the outer portions of the poles. Steaming proved an efficient mechanism to remove creosote. Some other technology must be applied to remove creosote content below 1.31%

Hydrothermal Treatment of CCA- and Penta-Treated Wood

Two of the three most commonly used wood preservatives in the United States are chromated copper arsenate (CCA) and oil-borne pentachlorophenol (penta). Both are excellent preservatives for extending the service life of exterior wood. Both also pose environmental problems associated with their disposal. This paper describes the treatment of two different groups of preservative-treated wood (CCA type C and oil-borne penta) in anaerobic supercritical water (SC) under acidic and basic conditions, respectively. A decommissioned (ca. 13 yr) southern pine (Pinus sp.) guard rail impregnated with CCA and a freshly treated pentaimpregnated pole were examined. During SC treatments, wood particles were transformed (approx. 98% efficiency) into liquid and gaseous hydrocarbon (HC) phase. The metals recovered in the two liquid phases vs. total concentration in the wood were as follows: copper: 91% AQ; < 1% HC, chromium: 28% AQ; 1.3% HC, and arsenic: 69% AQ; < 1% HC. The penta wood yielded a similar hydrocarbon mixture, with the chlorinated phenols undergoing dechlorination and further reaction. The formation of phenolic condensation products such as chlorinated dibenzofurans and dioxins occurred under these conditions when the reaction was run in quartz-lined containers and metals were excluded from the reaction mixture. When iron (either from the reactor walls or added in quartz cells as iron particles) was present, these products were not observed

Shrinkage of Outerwood, Middlewood, and Corewood of Two Sweetgum Trees

Two sweetgum (Liquidambar styraciflua L.) trees were used to determine the shrinkage properties of green outerwood, middlewood, and corewood. Samples were taken at various heights along the boles from each side of a disk. Shrinkage displayed the following general pattern: corewood > middlewood > outerwood. This pattern was reversed for the specific gravity of samples from each of these wood types from tree 1, but tree 2 maintained a relatively uniform specific gravity among wood types

Effect of Hardwood Vessels on Longitudinal Moisture Diffusion

The hypothesis that the longitudinal moisture content profile follows the shape of the sorption isotherm under steady-state diffusion condition was confirmed. This phenomenon was explained in terms of the unrestricted flow of water vapor from the lumen of one vessel element to the lumen of the next vessel element. Despite the assumed high vapor transport efficiency of the vessels, other cell types were believed to contribute substantially to longitudinal moisture movement. The diffusion coefficients of three different hardwood species were found to vary with moisture content

Theoretical Modeling and Experimental Analyses of Laminated Wood Composite Poles

Wood laminated composite poles consist of trapezoid-shaped wood strips bonded with synthetic resin. The thick-walled hollow poles had adequate strength and stiffness properties and were a promising substitute for solid wood poles. It was necessary to develop theoretical models to facilitate the manufacture and future installation and maintenance of this novel engineered wood product. A higher-order governing differential equation (GDE) model was developed for this purpose based on the principle of minimum potential energy. Transverse shear and glue-line effects were taken into account in the development of the model. A simplified theoretical model was also derived to further validate the higher-order GDE model. Thirty-six small-scale wood laminated composite poles were made and tested to validate the models developed. Strip thickness and number of strips were chosen as experimental variables. The deflection predicted by the theoretical models agreed well with those measured in experiment. The agreement with the results predicted by the simplified theoretical model was better than that with those predicted by the higher-order GDE model