Recycling and disposal of timber treated with waterborne copper based preservatives
J A Cornfield, S Vollam, P Fardell
Recycling and disposal technologies are briefly reviewed. Details are given of chemical extraction techniques suitable for recovery of copper from timber treated with a new copper based preservative, and traditional chromium based products. Details of thermal decomposition tests according to the DIN 53436 protocol under flaming and non-flaming conditions are given. The decomposition products were analysed for C0, CO2,O2, NOx and arsine. Preservative treated timber showed higher mass loss than untreated timber at 400°C indicating that oxidation was promoted by the presence of preservative at this temperature. At 800°C, 99% mass loss occurred in all cases. Gas analysis showed little difference in combustion products and oxygen uptake between treatments at both temperatures. No arsine gas was detected in the decomposition products of CCA treated timber. A further series of burning tests was carried out to determine the fate of the heavy metals in treated timber samples during thermal decomposition, and to determine suitable extraction techniques to recover the metal for recycling from the residual ash. Using a new copper based preservative the residual copper in the ash had very low water solubility, whereas quantitative extraction could be obtained using acidic extraction techniques. Findings regarding arsenic recovery from CCA treated timber were comparable with those reported by other workers.