Counter-current acid leaching process for copper azole treated wood waste

Abstract

This study explores the performance of a counter-current leaching process (CCLP) for copper extraction from copper azole treated wood waste for recycling of wood and copper. The leaching process uses three acid leaching steps with 0.1 M H₂SO₄ at 75°C and 15% slurry density followed by three rinses with water. Copper is recovered from the leachate using electrodeposition at 5 amperes (A) for 75 min. Ten counter-current remediation cycles were completed achieving≥94% copper extraction from the wood during the 10 cycles; 80–90% of the copper was recovered from the extract solution by electrodeposition. The counter-current leaching process reduced acid consumption by 86% and effluent discharge volume was 12 times lower compared with the same process without use of counter-current leaching. However, the reuse of leachates from one leaching step to another released dissolved organic carbon and caused its build-up in the early cycles.

Keywords:

• copper azole
• wood waste
• treated wood
• leaching
• copper

Acknowledgements

Sincere thanks are extended to the Natural Sciences and Engineering Research Council of Canada for their financial contribution to this study. Thanks are also due to Hydro Quebec and FPInnovations for valuable advice and guidance in this work.