Copper to quat ratio in alkaline copper quat (ACQ) wood preservative - Effects on fixation and leaching of preservative components in red pine
S Pankras, P A Cooper, T Ung, L Awoyemi
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.
Keywords: copper, quat, alkaline copper quat, ACQ, fixation, leaching, ratio