Multi-technique characterization of chromated copper arsenate-treated wooden utility poles from the Brazilian electricity network

Abstract

In this work, CCA-treated wooden utility poles were removed from the electricity distribution network and characterized in detail. The pole was split in different ratios of sapwood to heartwood. The characterization was performed through constituent, proximate, and ultimate analysis via X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and inductively coupled plasma atomic emission spectroscopy (ICP-OES). The results demonstrate the differences in the chemical composition of the fractions, especially concerning the amounts of extractives and holocellulose. The FTIR spectra contain the characteristic absorption bands of wood fibers. As shown by the ICP-OES measurements, the gradient of metal concentrations is steep in the radial direction of the pole, tending to zero at the centerline. The XRD measurements reveal that the external sapwood parameters increased because of the lack of chain mobility and crosslinking, which is promoted by the presence of metals. The TGA measurements of the samples of the external pole fraction show initial degradation temperatures similar to those reported for samples with high metal concentrations, while the core samples show a behavior similar to untreated wood. Consequently, the external pole fraction must be treated and disposed of correctly. The low concentration of metals in the internal fractions allows them to be used in conventional biomass processes.