The Microdistribution of Copper, Chromium and Arsenic in CCA Treated Wood and Its Pyrolysis Residue Using Energy Dispersive X-Ray Analysis in Scanning Electron Microscopy

Abstract

Scanning electron microscopy coupled with energy dispersive X-ray analysis is used to study the preservative distribution and the anatomical structure at the micro-level in CCA treated wood and its pyrolysis residue. The type of wood used in these analyses is Pinus sylvestris peeling and sapwood, treated with chromated copper arsenate. The sapwood was treated only once instead of twice as was done with the peeling. Examination of the peeling reveals a uniform distribution of the metals throughout the total volume of the peeling due to the porous structure, which enables the CCA solution to penetrate deep into the wood, and which explains the high retention level of CCA solution. The relative amounts of Cr, Cu and As which occur at different locations vary and differ from the ratio in the CCA treating solution. The same conclusions can be drawn for the pyrolysis residue resulting from pyrolysis of the CCA treated peeling, in which vestures and warty layers are observed. Examination of the CCA treated sapwood reveals lower metal concentrations due to the lower retention level of CCA solution during treatment. The three metals are also found at each location examined. The anatomical structure of sapwood differs from peeling in the sense that it is less porous and clusters containing predominantly copper can be observed. The pyrolysis residue of CCA treated sapwood has a more porous structure and the metals are more concentrated in the ray cells, indicating a migration of metal compounds during the pyrolysis process. Tears are also observed, probably as a result of the thermal degradation process.

Combustion Emissions Analysis of Wood-Based Waste Processing-Materials

“…This is attributed to the fact that the particles are wood and are a carbon-hydrogen compound. (Shirokae & Samezima, 1996;Helsen & Bulck, 1998). The same tendency was evident for the CCA and ACQ specimens (Fig.…”

“…Because wood preservatives are generally produced with various chemical compounds, it is necessary to understand the composition of the gases that are emitted when burning these preservative-treated woods, and the amount of char formed (residual metal) during combustion (Jang, 1997;Kercher & Nagle, 2001;Humphrey, 2002). The recognition of the need for abatement of air pollution has led to further interest in, and investigation of combustion as a major issue when disposing of cellulose wastes and cellulose residual materials (Helsen & Bulck, 1998). Regardless of waste minimization efforts, improved disposal-end management practices will play a key role in minimizing the impacts of disposed of CCA-treated wood in the next 25 to 40 years (Cooper et al, 2003), and of the ACQ-treated woods as well (Lin et al 2006).…”

“…Basically, both woods treated with CCA or ACQ are considered to be a type of cellulose material (Humphrey, 2002). The recognition of the need to reduce air pollution has led to further interest in, and the investigation of the feasibility of combustion to dispose of cellulose wastes and residual materials (Helsen & Bulck, 1998). The results of the emission contents for Taiwania and the two types of treated woods are shown in Fig.…”

Formation of metal agglomerates during carbonisation of chromated copper arsenate (CCA) treated wood waste: Comparison between a lab scale and an industrial plant

“…Earlier scanning electron microscopy coupled to energy dispersive X-ray (SEM-EDX) analyses, performed by Helsen and Van den Bulck [3], have shown the formation of metal (Cr, Cu and As) agglomerates in the solid product resulting from lowtemperature (350 • C) pyrolysis of CCA treated wood. In that study, pyrolysis was performed in a lab scale batch fixed bed reactor, and the wood samples were impregnated specially for these experiments.…”

Two possible pathways for the release of arsenic during pyrolysis of chromated copper arsenate (CCA)-treated wood

“…To date, few researchers have reported on the pyrolysis of CCA-treated wood. Van den Broeck et al [29], Helsen et al [5,7], and Helsen and Van den Bulck [6,8,9] have conducted extensive studies on low temperature (300-450 • C) pyrolysis of CCA-treated wood. When applying pyrolysis to CCA-treated wood, the behavior of arsenic is of critical importance, particularly in terms of its volatilization.…”