Kinetic model of CCA fixation in wood. part II. The main reaction zone

Fixation of chromated copper arsenate type C (CCA-C) solution on wood, measured by hexavalent chromium reduction, follows different rates in different reaction zones. We identify two main zones: an initial reaction and a second main reaction. The main reaction zone in red pine (Pinus resinosa Ait.) starts once approximately 47% of the total Cr-VI in the impregnated CCA-C solution is fixed on wood matrix. The second main fixation reaction follows first-order reaction kinetics, and an Arrhenius type of correlation can be used in modeling the fixation kinetics. We obtained similar values of Arrhenius parameters for CCA-C concentrations of 1% and 3%. The activation energies for fixation reactions in the second zone were 87.6 and 88.1 kJ/mol for 1% and 3% CCA-C concentrations, respectively. The pre-exponential factors of the reaction rate constant were 2.7 x 10(13) and 2.2 x 10(13) h(-1) for 1 and 3% solutions, respectively. By combining the reaction rate equations and the temperature-dependence (Arrhenius) relationship, a mathematical model for the main reaction of 1% CCA-C fixation in red pine was produced. This model estimates the percentage of CCA-C solution fixation on red pine for a given time (in hours)/temperature (K) history of the wood following treatment.