Leaching and chemical redistribution of CCA components in refractory heartwood of E. nitens

Chromated Copper Arsenate (CCA) is a wood preservative widely used to protect against fungal and insect attack. The fixation mechanism of CCA involves complex chemical reactions, including the reduction of chromium (VI) to chromium (III) and the formation of insoluble complexes. Despite fixation efforts, a portion of CCA components tends to leach from treated wood, influenced by factors like wood dimensions, species, preservative retention, and environmental conditions. This study focused on the leaching behaviour and preservative migration of CCA-treated Eucalyptus nitens (shining gum) under repeated wet/dry cycles.
Experimental methods involved preparing CCA-treated wood samples, subjecting them to accelerated weathering with simulated rainfall, and assessing leaching rates. Results indicate that arsenic exhibited the most leaching, while chromium showed the lowest. Leaching patterns were found to be highest at the initial rainfall cycles. The study also highlighted the significance of wood species, structure, and extractives in fixation and leaching behaviour.
The research examined the development of checks on wood surfaces, demonstrating the potential for preservative migration. The findings suggest that minor amounts of CCA components redistributed into check surfaces. Nonetheless, those values were negligible and the observed variations in values did not differ statistically from background levels. Comparative analysis with other studies indicated consistent leaching patterns, emphasizing the low leachability and effective fixation of CCA. The study contributes valuable insights for understanding leaching patterns and chemical migration, especially for hardwoods, and sheds light on the potential for value-added applications of CCA-treated shining gum in alternative markets.