Factors affecting sodium hypochlorite extraction of CCA preservative components from out of service treated wood for recycling
E D Gezer, P A Cooper
Significant amounts of chromated copper arsenate (CCA) treated wood products such as utility poles and residential constructions remain in service. There is an increasing public concern about environmental contamination from CCA treated wood when it is removed from service for reuse or recycling, placed in landfills or burned in commercial incinerators. In this paper, we investigate the effects of time, temperature and extractant concentration on chromium oxidation and extraction of CCA-C components from treated wood using sodium hypochlorite. Of the conditions evaluated, reaction of milled wood with sodium hypochlorite for one hour at room temperature followed by heating at 75°C for two hours gave the highest extraction efficiency. An average of 95 % Cr, 99 % Cu and 96 % As could be removed from CCA-C treated milled wood by this process. Most of the extracted chromium was oxidized to the hexavalent state and could therefore be recycled in CCA treating solution. Sodium hypochlorite extracting solutions could be reused several times to extract CCA components from new treated wood samples.