The influence of cation and anion structure of new quaternary ammonium salts on adsorption and leaching

This study examined the effect of cation and anion chemical structure of new quaternary ammonium and imidazolium compounds (QAC, bis-QAC, IC, bis-IC) on the adsorption onto Scots pine wood (Pinus sylvestris L.) and resistance to water leaching. The group of copper (II) modified QACs, containing copper-chloro-acetate complexes in the anion structure, was also examined. The length of alkyl hydrophobic substituents in the cation structure significantly influences adsorption. The adsorption characteristics were statistically related to the alkyl chain length of new quaternary ammonium salts (quantitative correlations between CMC and adsorption values). Bis-ICs adsorb onto Scots pine wood with the greatest difficulty and the slowest and are also leached to the greatest degree. A varied adsorption of chloride ion cations and a several times higher leaching of chlorides than cations of the examined salts from the saturated wood were observed. The anion modification of bis-QAC and bis-IC of copper-chloro-acetate complexes causes decreased adsorption and resistance to the leaching of these salts. As a result of the performed regression analysis of Langmuir and Freundlich adsorption isotherms, it was found that the adsorption of the examined compounds onto wood was governed by both chemical and physical processes. New quaternary ammonium and imidazolium compounds represent potential wood preservatives.