Electrodialytic removal of Cu, Cr, and As from chromated copper arsenate-treated timber waste

Waste of wood treated with chromated copper arsenate (CCA) is expected to increase in volume over the next decades. Alternative disposal options to landfilling are becoming more attractive to study, especially those that promote reuse. The authors have studied the electrodialytic removal of Cu, Cr, and As from CCA-treated timber waste. The method uses a low-level direct current as the 'cleaning agent', combining the electrokinetic movement of ions in the matrix with the principle of electrodialysis. The technique was tested in four experiments using a laboratory cell on sawdust of an out-of- service CCA-treated Pinus pinaster Ait. pole. The duration of all the experiments was 30 days, and the current density was kept constant at 0.2 mA/cm². The experiments differ because in one the sawdust was saturated with water (experiment 1) and in the rest it was saturated with oxalic acid, 2.5, 5, and 7.5% (w/w), respectively, in experiments 2-4. The highest removal rates obtained were 93% of Cu, 95% of Cr, and 99% of As in experiment 2. Other experimental conditions might possibly optimize the removal rates.