Leaching from new generation treated wood: a chemical approach

Abstract

Leaching of biocides from construction products is currently a research topic receiving attention from the European regulation authorities (CEN/TC 351). In this paper we have focused on the leaching behaviour of CBA (copper-borateazoles) treated Pinus sylvestris. To better define the chemistry of the leaching phenomena, two leaching tests (a static equilibrium test and a dynamic surface leaching test) have been carried out on untreated and treated wood, which offered more information about how the leaching of biocides interferes with other substances released from the wood structure. Eluates, in liquid and lyophilised form, were further analyzed by analytical methods. Organic (tebuconazole) and inorganic (Cu, B) biocides were quantified and several organic compounds have been identified (e.g. carboxylic acids, phenols, amines, etc.). Also, the total amount of phenols and of carboxylic groups was determined. Results on inorganic compounds are in accordance with previous studies made on treated wood. Furthermore, organic carbon, tebuconazole and other organic compounds' behaviour was extensively investigated. This study aims to complete existing leaching data and to help developing a chemical model for several biocides in wood, including Cu, B and tebuconazole.

The extent of tebuconazole leaching from unpainted and painted softwood

“…[6][7] TAZ leaching likely occurred through its molecular association and co-elution with wood extractives, such as carboxylic acids, alcohols, phenols, and ketones. 5,7 TAZ was also found to be physically dislodged from pressure-treated wood by rain as opposed to its dissolution in water. 7,19 Previous studies focusing on TAZ leaching mainly used wood co-treated with copper and other metals; 5-10 however many wooden products, such as windows, are treated with formulations that do not contain metals.…”

“…1 While the leaching behavior of inorganic preservatives has been extensively studied, [2][3][4] leaching of organic preservatives has been investigated to a lesser extent, and was limited to pressure-treated wood using mainly metal-containing formulations. [5][6][7][8][9][10] Triazoles such as tebuconazole (TAZ) and propiconazole are among the most frequently used organic wood preservatives, [11][12][13][14][15] thus determination of their leaching potential under various conditions is warranted.…”

“…[16][17][18] In general, the leaching process is characterized by preservative partitioning between the wood and the aqueous phase (mobilization), followed by its diffusion through the wood porous matrix. 5 Studies performed by Lupsea et al using a copper-borate-azole formulation showed that TAZ fixation within wood was pH dependent and thus suggested hydrogen bonding of TAZ with the carboxyl and phenolic groups of wood. [6][7] TAZ leaching likely occurred through its molecular association and co-elution with wood extractives, such as carboxylic acids, alcohols, phenols, and ketones.…”