Distribution coefficients for the liquid-liquid extraction of 2,3-butanediol (5 wt%) in aqueous solutions with binary mixtures of 4-nonylphenol (0-67 vol%), toluene and several alcohols, (2-ethyl-1-hexanol, 1-octanol and 1-decanol) at 25 degrees C are reported. The distribution coefficients were in the following ranges: 4-nonylphenol + toluene (0-0.23), 4-nonylphenol + 2-ethyl-1-hexanol (0.23-0.27), 4-nonylphenol + 1-octanol (0.21-0.33) and 4-nonylphenol + 1-decanol (0.22-0.37). The largest distribution coefficient was found to be 0.37 for the mixed solvent 4-nonylphenol + 1-decanol (50 vol%), which shows a slight decrease in the separation factor. Activity coefficients at infinite dilution were determined using the MOSCED model and a similar trend for all the solvent mixtures of 4-nonylphenol and alcohols was found.