Remediation of ACQ-treated wood waste by Mea extraction

Abstract

This study investigated the use of monoethanolamine (Mea) solution to extract copper from alkaline copper quat (ACQ)-treated wood. Mea could extract more than 90 % of copper from ACQ-treated wood. The formation of stable neutral Cu(Mea)2 in Mea solution is the main mechanism for Mea extraction. The effects of process parameters: pH, Mea concentration and temperature were also studied. Higher Mea solution pH resulted in higher Cu extraction efficiencies until pH 10. Cu extraction efficiency increased moderately to 10 % Mea concentration but not significantly above this. Mea (10–15 %) extraction at the original pH (around 12) was fast, and the effect of extraction temperature was insignificant for small particles of treated wood and detrimental for larger pieces. Based on empirical data and application of theoretical diffusion models with larger specimens, extraction was faster in the longitudinal direction than for the other wood directions. Since the extract solution containing ACQ components can potentially be reused as fresh treating solution after the proper supplement of Cu–amine solution, this approach is the most straightforward procedure for the recycling of chemicals removed from ACQ-treated wood.