Solvent extraction of CCA-C from out-of-service wood
K M F Kazi, P A Cooper
Elimination of CCA from decommissioned wood prior to disposal is a major environmental issue. One approach is to extract CCA from treated wood, then reuse the 'clean' (may contain CCA, but below hazardous level) wood materials for manufacturing wood-based composites. In the present paper, we focus on effective leaching processes, selection of leaching agents and optimum leaching process parameters (temperature, time and reagent concentrations). These factors are crucial in obtaining high strength 'environmentally clean used wood substrate' suitable in manufacturing boards. Some leaching agents selectively leach certain components of CCA. Different combinations and sequences of leaching were evaluated. All treatments leave significant amounts of some CCA components in the wood, although some combinations of solvents can extract about 90% of all CCA components in 4 hours at a temperature of 50°C. Sequential extraction using formic acid and oxalic acid was one especially effective combination. Solution temperature, concentration and leaching time affect CCA component removal in different ways, depending on the solvent and element extracted. It should be possible to optimize extraction by manipulating these variables.