INTERACTIONS OF AMMONIACAL COPPER-ZINC ARSENATE (ACZA) WITH DOUGLAS-FIR

Tests were conducted to determine the effect of ACZA composition on fi xation and the roles of adsorption and precipitation in fixation. The sites of copper and zinc adsorption within the treated wood and the bo nding environment of adsorbed copper were also examined. The results g enerally support the finding that arsenic fixation occurs by precipita tion of metal/arsenate complexes. Arsenic leaching was minimized with high solution ratios of metal oxide:arsenic pentoxide, and with formul ations containing zinc. Zinc precipitated the majority of arsenic when ammonia was allowed to evaporate from the treating solution. The meta l cations were leach-resistant regardless of ACZA formulation because of their low water solubility and their ability to adsorb to the wood. Copper was readily adsorbed by lignin and by model compounds that pos sessed phenolic hydroxyl groups, which suggests that phenolic hydroxyl groups were the primary reaction sites. Fourier Transform Infrared (F TIR) and Fast Atom Bombardment (FAB) mass spectroscopy analysis also s upported this conclusion. Multiple copper species and increased free r adical content were detected within lignin that had adsorbed copper. A dsorption of copper and zinc has important ramifications for arsenic f ixation.