Adsorption of ACQ components in wood

IRG/WP 10-30522

Myung Jae Lee, P Cooper

To investigate the chemical adsorption capacity of copper-monoethanolamine (Cu-Mea) components on wood, the Na+ cation exchange capacity (CEC) of red pine (Pinus resinosa Ait.) was determined and compared to the adsorption capacity of free Mea and Cu-Mea complexes. The CEC increased with increasing pH. Free Mea adsorption as a function of pH followed the sodium adsorption curve except at pH over 9, when it exceeded the CEC. Cu-Mea adsorbed up to the CEC at pH 9.0-9.5 apparently as Cu(Mea)+, whereas the complex in solution is predominantly of the form Cu(Mea)2+. For the quaternary ammonium compound, alkyl dimethyl benzyl ammonium chloride (ADBAC) adsorption isotherm showed two different adsorption mechanisms into wood: ion exchange reaction at low concentration and hydrophobic interaction at high concentration. ADBAC adsorbed at solution concentrations below a critical concentration (hemi-micelle concentration) had high leaching resistance while ADBAC adsorbed into wood at above the critical micelle concentration (CMC) had low leaching resistance. The CMC decreased with addition of Mea and Cu-Mea. The anion, Cl- of ADBAC was only adsorbed at solution concentrations above the CMC and was easily leached out. The adsorption capacity of ADBAC into wood by cation exchange reaction did not achieve the cation exchange capacity (CEC) of wood. However, the total adsorption of ADBAC and Cu achieve the CEC of wood in the presence of copper amine, and ADBAC competes with copper to occupy the same sites in wood.

Keywords: cation exchange capacity (CEC), copper amine, ethanolamine, alkyl dimethyl benzyl ammonium chloride (ADBAC), critical micelle concentration (CMC), quaternary ammonium compound (quat)

Conference: 10-05-09/13 Biarritz, France

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