Biocide leaching from CBA treated wood - a mechanistic interpretation

Area of Science:

• Wood Preservation Science
• Environmental Chemistry
• Material Science

Background:

• Treated wood is widely used in construction, necessitating an understanding of biocide safety for human health and the environment.
• Copper-boron-azole (CBA) is a wood treatment containing tebuconazole (organic biocide) and monoethanolamine (Mea).

Purpose of the Study:

• To investigate the chemical mechanisms of fixation and mobilization of inorganic and organic biocides during the leaching of CBA-treated Pinus sylvestris.
• To identify and quantify species released from wood using pH-dependent leaching and complementary analysis.

Main Methods:

• pH-dependent leaching tests were conducted on wood treated with copper-boron-azole (CBA).
• Complementary analytical methods were employed to identify and quantify released species.
• Analysis focused on organic compounds, nitrogen-containing compounds (Mea), copper, tebuconazole, and boron.

Main Results:

• Organic compounds, including carboxylic and phenolic functions, increased with pH. Nitrogen compounds (Mea) were significantly released at low pH.
• Copper leaching exhibited pH dependency due to competitive complexation and protonation reactions. Tebuconazole release was limited, influenced by pH-dependent wood interactions.
• Boron release was high and pH-independent, confirming weak fixation and minimal interaction with wood extractives.

Conclusions:

• The study elucidates the complex leaching behavior of CBA biocides, highlighting pH as a critical factor influencing their environmental mobility.
• Understanding these mechanisms is crucial for assessing the environmental impact and efficacy of treated wood products.
• Differential fixation and release patterns of copper, boron, tebuconazole, and Mea necessitate specific considerations in wood preservation and risk assessment.