Removal of copper, chromium and arsenic from preservative-treated wood by chemical extraction-fungal bioleaching

Large volumes of preservative-treated wood containing toxic Cr, Cu and As salts are decommissioned worldwide. This study investigated the effectiveness of solid-state fermentation with copper-tolerant brown-rot fungi for the remediation of wood treated with chromated copper arsenate (CCA) and acid copper chromate (ACC) formulations. Treatment of CCA- and ACC-wood with the most effective strain, Antrodia vaillantii FRLP-14G, attained extensive leaching of As and/or Cr, but Cu elimination was poor (<18%). Additional research showed that a variety of organic acids, including citrate, are effective Cu extractants. Based on these findings, a process combining chemical extraction and subsequent fungal treatment was developed that proved highly effective in removing inorganic pollutants from CCA-wood. Extraction of CCA-wood with citric acid (30 mM, pH 3.10) followed by a 28-day solid-state fermentation period removed 87% Cu, 80% Cr, and 100% As. These results indicate the potential of the two-stage process for the remediation of preservative-treated wood.