Chemical analysis of CCA-C treated wood residues, charcoal and wood tar

Abstract

After its useful life, treated wood residues can be toxic, and its disposal, often incorrect, and several countries have researched measures to reuse or recycle it. This study evaluated the potential for pre-extraction of chromated copper arsenate (CCA-C) treated wood for combustion, either direct landfilling or agricultural use (organic compost or biochar). Treated wood residues were transformed into 0.5 × 3 × 3 cm chips (tangential × radial × longitudinal). A portion of these were crushed in a Wiley mill and the other, charred. Charcoal, charring by-products, and sawdust were evaluated for the amount of CCA-C present in them. Sawdust and crushed charcoal were extracted by 0.1 mol L−1 sulfuric and acetic acid, and sodium and potassium hydroxide solutions for two, four, or six hours. The material was, then, washed and the amount of CCA-C analyzed. Sulfuric acid extraction for six-hour obtained the best results. The methodology used extracted more preservative from wood than charcoal and part of the oxides were released into the atmosphere during the carbonization of treated wood, since the wood tar obtained CCA-C. The results obtained for both wood and charcoal were insufficient to render the residues safe, after removing the CCA-C components. After extraction, we considered the resultant wood and charcoal effluents hazardous, demanding greater attention in their disposal.