Counter-current process for cca-treated wood decontamination and treatment of effluent generated by electric recovery and precipitation

The preservative Chromate Copper Arsenate (CCA) has been used as an alternative for wood preservation to increase its durability, generating a large volume of effluents at treatment plants and in during the decontamination of treated wood. Due to the presence of high concentrations of toxic elements (Cu, Cr and As) these effluents must be treated before being disposed of. Thus, the aim of this study was to develop an effective wood decontamination method based on the counter-current process, reusing the effluents and rinsing water in each extraction cycle. Additionally, total precipitation of the 3 elements and electric recovery of Cu for the extract of the counter-current process were also studied. Removal of the elements by precipitation produced percentages higher than 98.5%. About 91% of Cu was recovered from the effluent when a current of 5 A was applied for 90 min. The results indicated that the counter-current process was efficient in acid decontamination of CCA-treated wood and the proposed treatments produced an effluent suitable for reuse or disposal, in accordance with environmental legislation. © 2020 University of Sao Paolo. All rights reserved.