The chemistry and kinetic behavior of Cu‐Cr‐As/B wood preservatives. II. Fixation of the Cu/Cr system on wood

Abstract

Abstract The kinetic behavior of a Cr 6+ /Cu 2+ system in its reaction with wood has been elucidated. The same reactions with carbohydrates and lignin of wood for Cr VI alone are still present. Approximately 20% of the copper is fixed to the guaiacyl units of lignin in the form of copper chromate; the remaining copper forms complexes with cellulose and mainly with the guaiacyl units of lignin. The Cr VI /lignin guaiacyl unit complexes already found for the treatment of wood with CrO 3 are still the main Cr VI complexes formed. Copper chromate is present as [Cu(H 2 O) 2 (guaiacol)]CrO 4 (guaiacol) complexes, and CuCrO 4 bridges between different guaiacyl units of the lignin network appear to be likely. Substantial interference of the Cu 2+ ions in the second‐zone reactions of Cr VI with wood occurs. The amount of Cr VI and Cr III fixed onto lignin and cellulose compares well with experimental values. Rate constants, energies of activation, and Arrhenius equations of the various reactions have been obtained. The amount of Cu 2+ interference in the reaction has also been calculated.