Removal of toxic metals from discarded CCA treated timber

Summary

Objective

The aim of this project is to develop an environmentally friendly and sustainable method for the extraction of toxic metals from discarded CCA-treated timber. The project will develop and utilise a green lixiviant with specific chemical properties that can leach out chromium, copper, and arsenic from CCA timber. Subsequently, electrolysis techniques will be applied to extract these metals from the leachate solution before the final disposal of the spent lixiviant. Based on the preliminary results, our lixiviant was able to leach about 90% of chromium, copper, and arsenic within 3 hours and the subsequent electrolysis techniques (chemical-free method) were able to remove 95% of the target metals from the impregnated lixiviant within 2 hours. This approach will ensure the safe disposal of discarded CCA treated timbers as well as associated liquid waste to ensure sustainability.

Background

Spent chromated copper arsenate (CCA) timber is a big burden for vineyards. Around 1.3 – 3.3 million CCA vine posts or 12,000 – 30,000 tonnes are broken and taken out of service each year, and typically stockpiled on the property. Over time, CCA treated timber can release these metals into the environment, posing a risk to soil health, groundwater, and ultimately the vineyard ecosystem. The ability to sustainably extract the preservative (chromium, copper, and arsenic) may provide an alternative circular end-of-life pathway compared to traditional landfill.