Effects of fixation conditions and seawater on leaching of wood treated with marine retention CCA

IRG/WP 97-50088

S T Lebow

The effect of post-treatment conditioning temperature and humidity on leaching of chromated copper arsenate (CCA) was compared in seawater and deionized water. Southern pine cubes treated to 40 kg/m3 CCA were stored at 2° C and 82% relative humidity (RH), 24° C and 65% RH, or 32° C and 30% RH for 3, 10, or 17 days. Cubes were then leached in deionized water or artificial seawater. The rate of leaching of CCA components, especially copper and chromium, was strongly influenced by fixation time and conditions. Fixation was most rapid for arsenic, possibly due to an increase in the proportion of available chromium at the high marine retention. Conversely, the percentage of leached chromium was strongly affected by fixation time and temperature, and was consistently higher than that of copper and arsenic when samples were conditioned at cold (2° C) temperatures. There was little difference in leaching rates between blocks stored at 24° C and 65 RH and those stored at 32° and 30 RH after 10 or 17 days, possibly because of the low wood moisture content in the warmer room. The rate of chromium leaching was similar for seawater and deionized water. However, copper leaching was greater in deionized water. Possible reasons for the differences between copper leaching in the two media are discussed.


Keywords: CCA-C; MARINE RETENTION; LEACHING; FIXATION CONDITION; SEAWATER

Conference: 97-05-25/30 Whistler, British Columbia, Canada


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