Testing a diffusion and reaction model for the leaching of CCA components from unfixed CCA-treated wood

IRG/WP 02-50193

L Waldron, P A Cooper

A previously described physical model applicable to the leaching of any substance undergoing a first-order fixation reaction with wood is applied to the leaching of CCA components from unfixed wood. Using this model and laboratory leaching experiments with small wood samples immersed in water, the diffusion coefficients and reaction rate constant of Cr6+, total Cr, Cu and As in unfixed CCA-treated red pine (Pinus resinosa Ait) are measured. Modelled reaction rate constants are in general agreement with pure fixation experiments except when determined from experiments involving small samples severely depleted by longitudinal leaching, but this effect is seen to decrease for larger sample sizes. The operation of the model for predicting intermittent Cr6+ leaching is explained through a visual demonstration. The model is shown to have good predictive ability when compared to a leaching experiment involving intermittent immersion and changing temperatures.


Keywords: CCA, leaching, modelling

Conference: 02-05-12/17 Cardiff, Wales, UK


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