Sorption of a triazol derivative by soils: importance of surface acidity

The sorption of a triazol derivative, 1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1, 2,4-triazol-1-yl) penten-3-ol with a common name of S3307D, on fifteen soils and three H2O2-treated soils was investigated. The sorption isotherm for each untreated and treated soil was nonlinear, and was best fitted to Freundlich sorption equation. Soils containing high amount of clay content or organic matter or both sorbed much higher amounts of the chemical than soils that had low contents of these soil constituents. H2O2-treated soils showed considerable sorptive affinity for S3307D. It was concluded that both organic matter and mineral fraction in natural soils contributed to the sorption of the basic compound. Sorption by the H2O2 treated soils increased as suspension pH decreased, but all suspension pHs exceeded the pKa of the compound by more than two units. This implies that organic base protonation can occur on-surfaces of soil components, and surface acidity (exchangeable acidity) is important in sorption process of the organic base rather than suspension pH.