OXIDATION OF WOOD COMPONENTS DURING CHROMATED COPPER ARSENATE (CCA-C)FIXATION

Pre-extracted radial sections of southern yellow pine sapwood were tre ated with CCA-C and analyzed by x-ray photoelectron spectroscopy (xps) . The ratio of C1 (carbon bonded only to carbon and/or hydrogen) to C2 (carbon bonded to one oxygen with a single bond) was used to determin e the progress of oxidation of wood components during CCA fixation. Th is ratio increased after treating times of 10 minutes and 60 minutes a nd decreased after 180 minutes soaking suggesting that oxidation of C2 predominates on initial contact with CCA solution but oxidation of C1 (lignin) becomes more important with extended exposure to the treatin g solution. Oxidation of C2 to C3 (carbon bonded to two oxygens or a c arbonyl group) was demonstrated by in situ trapping of C3 with ethylen e glycol as it was formed. Further oxidation of C3 to C4 (carboxylic c arbon) was not observed in the xps spectra, consistent with the findin gs of others. The hypothesis that rapid decarboxylation results in los s of C4 as evolved CO2 is supported by the observation that the C4 com ponent of untreated wood was reduced by more than 90% after 10 minutes of CCA soaking followed by high temperature fixation and by the obser vation of CO2 evolution during early stages of accelerated fixation. T he Cr(2p) spectra of Cr-VI and Cr-III were established at 580.2 and 57 7.8 eV respectively. Accelerated fixation of CCA-C treated specimens r esulted in a very high degree of reduction of Cr-VI to Cr-III. XPS Cu (2p3/2) peaks were established at 935.1 for CCA-C, 935.3 for Cu(OH)(2) , and 933.7 for CuO. Cu (2p3/2) peaks in CCA-treated wood were shown a t 932.9 with no satellite peaks for the 10-60 minutes soaking in CCA s eries, and at 933.9 and 936.4 with satellite at 941-948 for the 3 hour s soaking time. The latter are attributed to complexed copper oxide an d hydroxide forms of Cu-II. Peaks attributed to Cu-II hydroxides were shown to diminish in leached samples.