Effect of pyrolysis on solvent extractability of toxic metals from chromated copper arsenate (CCA)-treated wood.

Solvent extraction was conducted to investigate the behavior of toxic metals in chromated copper arsenate (CCA)-treated wood and its pyrolysis residue. Four kinds of solvents, along with sulfuric and phosphoric acid as mineral agents, and citric and oxalic acid as complexing agents, were used. The CCA elements from the wood treated without pyrolysis were easily extracted. However, only a small amount of CCA elements were extracted from the pyrolyzed residue, even under very low pH conditions. The toxic elements in the pyrolyzed wood showed high stabilization against the solvent extraction. Pyrolysis strongly immobilized the toxic elements in the residue. Therefore, pyrolysis is not suitable as a pretreatment.