Removal of toxic elements from wastewater generated in the decontamination of CCA-treated Eucalyptus sp. and Pinus canadense wood

The objective of this study was to apply extraction with hot sulfuric acid to remove Cu, Cr, and As from different species of wood treated with CCA and subsequently evaluate treatment processes for the effluents generated in acid decontamination. This study was conducted in two stages: the first involved applying acid extraction to decontaminate different species of Eucalyptus sp. and Pinus resinosa treated with CCA and the second stage consisted of optimizing the treatment of acidic effluents generated in this process based on precipitation and coagulation. When compared to the initial levels, As, Cu, and Cr removal in the three extraction cycles was over 79%. Classification tests were performed to determine decontamination of the solid wastes generated in the extraction process and the results were lower than the limit established for hazardous waste, according to local legislation. The decontaminated wood obtained in this process can be considered for disposal in landfills or potential reuse. Precipitation was performed using FeCl₃ as coagulant and NaOH or Ca(OH)₂ as alkalizing agents. The results indicated that the use of FeCl₃ and Ca(OH)₂ ensures compliance with environmental legislation for both effluents tested, allowing As, Cu, and Cr removal above 98.5%. These findings demonstrate that precipitation can be used to successfully remove toxic elements from wastewater generated by decontamination of CCA-treated wood, opening the possibility of applying this process on an industrial scale.