Implication of chromium speciation on disposal of discarded CCA-treated wood

Jinkun Song, Brajesh Dubey, Yong Chul Jang, Timothy Townsend, Helena Solo-Gabriele

Research output: Contribution to journalArticle

24 Scopus citations

Abstract

The wood preservative chromated copper arsenate (CCA) contains hexavalent chromium [Cr(VI)] and the conversion of Cr(VI) to trivalent chromium [Cr(III)] drives fixation of the treatment chemicals to the wood fibers. Since the toxicity of Cr depends on its valence state, an assessment of the Cr species occurring in CCA-treated wood, as well as leachates and ashes from CCA-treated wood, is helpful when assessing implications for disposal. In this study, both new and weathered wood samples of CCA-treated wood and their ashes were evaluated for total Cr and Cr(VI) within the solid matrices and within leachates. Results show that for both new and weathered CCA-treated wood, Cr(VI) occurred in the range of 0.7-4% of the total Cr. Greater Cr leaching occurred at the pH extremes, with Cr(VI) only measured under alkaline pH values (pH > 9.0). Total chromium concentrations from synthetic precipitation leaching procedure (SPLP) leachates from CCA-treated wood were consistently less than 3 mg/L with Cr(VI) below detection limits. The results suggest that leaching of Cr(VI) from discarded CCA-treated wood should not be a concern in most landfill environments. One exception would be disposal in landfills with alkaline leachate; Cr(VI) was observed to leach from CCA-treated wood in the presence of alkaline leachate from crushed concrete. When CCA-treated wood is combusted, chromium becomes concentrated in the ash. Cr(VI) in ash from the combustion of CCA-treated wood was found between 4 and 7% of the total chromium. In ash from the combustion of wood recovered from construction and demolition (C&D) debris (which contained some CCA-treated wood), Cr(VI) accounted for as much as 43% of the total Cr. Nearly, all of the Cr in SPLP leachates produced from the ash was in the Cr(VI) form. The degree of Cr(VI) leaching from the ash was highly dependent upon the alkalinity of the ash, with higher ash leachate pH resulting in greater concentrations of Cr(VI).

Original languageEnglish (US)
Pages (from-to)280-288
Number of pages9
JournalJournal of Hazardous Materials
Volume128
Issue number2-3
DOIs
StatePublished - Feb 6 2006

Keywords

  • Chromated copper arsenate
  • Chromium
  • Chromium speciation
  • Hexavalent chromium
  • SPLP
  • Treated wood
  • Trivalent chromium

ASJC Scopus subject areas

  • Chemical Health and Safety
  • Process Chemistry and Technology
  • Safety, Risk, Reliability and Quality
  • Environmental Engineering

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