Development of a sustainable method for the disposal ofudchromated copper arsenate (CCA) treated wood

摘要

Preserved wood is commonly found in solid waste. Among the different types ofudpreserved wood, CCA wood has received much attention due to the scale of usage and itsudsignificant role in soil and water contamination after disposal. As the ash of CCA wood isudhazardous, it cannot be burned, and the best available disposal method is thus landfilling.udLeaching of the metals from disposed CCA wood in landfills pollutes the environment.udTo reduce the contamination of CCA, treatment before landfilling is required.udNowadays, ethanol is seen as a promising source of energy. Lignocellulosic materialsudsuch as wood are resources for ethanol production. This research focuses on theudpossibility of producing ethanol from CCA wood. It suggests that production of ethanoludwill not only be a solution to the disposal but will also generate a clean fuel.udThe results showed the existence of copper, chromium and arsenic did not have audnegative effect on the fermentation, and producing ethanol from CCA wood is feasible.udThe copper removed by sulfuric acid completely precipitated during the hydrolysis andudivudneutralization. In addition about 50% of the chromium (VI) and also 60% of the arsenicud(V) were removed from the leachate by yeast during fermentation.udTCLP tests of the hydrolyzed wood leached less than 4 ppm of arsenic while minimaludamounts of chromium and copper remained in the hydrolyzed wood which makesudlandfilling of hydrolyzed wood acceptable.udBaker's yeast behaves selectively by uptaking arsenic (V) and chromium (VI) but notudarsenic (III) and chromium (III). There is competition between copper and chromiumudsorption by yeast. The kinetic model for removal of copper and chromium is a zero orderudmodel while the appropriate model for uptaking arsenic by yeast is a first order model.udThe kinetic models confirm that there are different mechanisms of uptaking metals byudyeast, a diffusion mechanism for removal arsenic and a surface adsorption mechanism forudcopper and chromium.udAs an overall conclusion of this study, using discarded CCA wood as the feed for ethanoludproduction is a sustainable method for disposal of CCA treated wood.