Effect of amine ligand, copper/amine ratio, and pH on copper adsorption into wood

Abstract

Abstract To measure the chemical adsorption capacity of wood for copper (Cu) and amine in Cu-amine solution, Cu was formulated with different ratios of mono- (Mea), di- (Dea), tri- (Tea) ethanolamine, ethylenediamine (En) and ammonia (Am), and the Cu adsorption was compared with the cation exchange capacity (CEC) of red pine (Pinus resinosa Ait.). The chemisorption capacity of the wood for Cu was highly pH dependant and varied with ligand types investigated in this study. Although wood chemisorption capacity increases with pH, high amine ratio Cu-ethanolamine complexes showed very limited adsorption at high pH owing to competition with free ethanolamine in combination with the formation of uncharged ion complexes. During Cu-Mea treatment, negligible Cu2+ was converted to Cu+ and no significant delignification was detected even at very high Mea ratios. Cu appeared to be adsorbed as if it were singly charged, even though most of the complexes present are 2+ charged. The three ethanolamine ligands generally showed similar adsorption tendencies, although their pH dependencies differed. Cu in En was much less adsorbed at intermediate pH compared with the CEC, but had higher adsorption at high pH. Cu in Am also showed higher adsorption at high pH compared with Mea and the [Cu(NH3)(H2O)5]2+ form of Cu might be fixed in wood.