X-Ray Diffraction as an Analytical Method in Wood Preservatives

Abstract

Summary X-ray diffraction (XRD) technique was used to analyze qualitatively and semi-quantitatively solid crystal deposits in wood treated with some preservatives. Chromated copper arsenate type-C (CCA), copper ethanolamine (Cu-EA), copper naphthenate (Cu-N), copper dimethyldithiocarbamate (CDDC) and boric acid treated southern pine was investigated. The solid deposit in post-treatment steamed Cu-N and Cu-EA treated wood samples was identified as cuprous oxide (Cu2O) by using XRD. The presence of CDDC crystals was observed in CDDC treated wood samples. The XRD pattern of boric acid treated wood shows that crystalline boric acid is present in the treated wood. After washing boric acid treated wood with distilled water, the crystalline signal of boric acid disappeared. An XRD technique was also developed to semi-quantify the amount of solid crystals in post-treatment steamed Cu-N treated and CDDC treated samples. It was estimated that about 50% of cupric copper was converted to cuprous oxide (Cu2O) in Cu-N treated wood after post treatment steaming whereas no cuprous oxide was found in non post-treatment steamed Cu-N treated samples. The CDDC content determined by XRD was consistently 10–20% lower than the value calculated from the copper content using atomic absorption spectroscopy (AAS) analysis.