This paper provides new insights into modelling the distribution of hydroph
obic compounds between soil and water phases in the presence of nonionic su
rfactant micelles. Experimental measurements were made of various systems c
omprising a non-ionic surfactant, five soils of different fractional organi
c carbon contents, and a hydrophobic (disperse) dye. Soil-washing performan
ce was quantified using reciprocal surfactant-soil solubilization coefficie
nts (1/K-d). Two stages of partitioning were identified. In stage 1, the dy
e concentration increased slightly with increasing surfactant dose until su
rfactant monomers saturated the bulk solution at the critical micelle conce
ntration (cmc). The washing performance was 1:1 proportional to the surfact
ant monomer concentration, Most of the surfactant in this stage is sorbed.
In stage 2, above the cmc, soil-washing performance increased linearly with
increasing available surfactant micelles in the bulk solution. Reciprocal
surfactant-soil solubilization coefficients (1/Kd), octanol-water partition
coefficients (K-ow), fractional organic carbon content of the soil (f(oc))
and surfactant concentration were correlated for each stage in the soil-wa
shing process using two simple equations. (C) 2001 Elsevier Science Ltd. Al
l rights reserved.