EFFECTS OF WOOD SPECIES AND RETENTION LEVELS ON REMOVAL OFCOPPER, CHROMIUM AND ARSENIC FROM OUT-OF SERVICE CCA TREATEDWOOD USING CALCIUM HYPOCHLORITE

摘要

Chromated copper arsenate (CCA) has been one of the most widely used since the 1933’s as a wood preservative to protect wood against decay and insects for exterior applications such as decks, housing, utility poles, play equipment and fences. Although its major use for consumer lumber products was replaced with chromium- and arsenic-free preservatives in the USA, Canada and European Countries by the end of 2003, large volumes of CCA-treated wood has been still coming out-of-service each year. Therefore, at present, the potential loss of heavy metals from CCA-treated wood waste after disposal has become an important problem. The disposal of out-of service CCA treated wood materials at the end of its useful life remains a concern, despite the reduction in CCA-treated wood production. Waste management options for out-of service CCA-treat wood are limited and include minor amounts of recycling and incineration with the remainder going to landfill disposal. Because of new regulations and the concerns about environmental contamination, there is a need in developing methods for recycling out-of-service CCA-treated wood products. Acid extraction, with or without bioremediation, has been extensively studied for removal of copper, chromium and arsenic from out-of service CCA-treated wood. However, none of the researchers addressed the problem about the effects of wood species and retention levels on remediation efficiency. The objectives of this study were to investigate the effects of wood species and retention levels on removal of copper, chromium and arsenic from CCA-treated wood samples using calcium hypochlorite. The results showed that Ca(ClO)2 was very effective to remove copper, chromium and arsenic from CCA-C treated milled wood samples for all three species used in this study. Ca(ClO)2 may be very good option to remediate out-of- service CCA treated wood not only because of its high and relatively fast extraction efficiency but also because the chemical is relatively inexpensive. However, the results showed that wood species and initial retention levels of CCA-treated wood products played very important role in terms of removal of Cu, Cr and As. Therefore, whichever the remediation methods and chemicals are used for the removal of Cu, Cr and As, initial retention levels of the CCA treated wood products should be taken into account and CCA-treated wood products should be sorted according to their initial retention levels and wood species (if possible) before remediation process.