Correlation and prediction of environmental properties of alcohol ethoxylate surfactants using the UNIFAC method

Environmental properties of one type of nonionic surfactants, the alcohol ethoxylates (polyoxyethylene alcohols), are predicted using the UNIFAC (universal quasi-chemical functional group activity coefficient) method. Various properties are considered; the octanol-water partition coefficient (K-ow), the bioconcentration factor (BCF), and the toxicity. K-ow values of alcohol ethoxylates are difficult to measure. Existing methods such as those in commercial software like ACD,(13) Clogp,(14) and KowWin(15) have not been applied to surfactants, and they fail for heavy alcohol ethoxylates (alkyl carbon numbers above 12). Thus, the K-ow, values are predicted here via UNIFAC and compared to the few available experimental data. Based on the predicted Kow values, a correlation between Kow and hydrophilic-lipophilic balance (HLB) is established because HLB is a widely used parameter in surfactant applications. Finally, BCF and toxicity of alcohol ethoxylates are correlated with their K-ow. The proposed approach can be extended to other families of nonionic surfactants.