The performances of aqueous mixtures of the model nonionic surfactant Triton X-100 (TX100) and chitosan (CS) for the solubilization of the hydrophobic organic compound phenanthrene (PHE) were evaluated by varying mixture compositions. The addition of minute amounts of CS into TX100 solutions above the critical micelle concentration significantly increased PHE solubility. The PHE solubility was maximized at certain optimal concentrations of CS increasing in proportion to the TX100 concentrations, which were 2, 10, and 20 mg/L CS for 5, 10, and 20 g/L TX100, respectively. At each optimal concentration of CS, PHE solubility was increased by 46%, 39%, and 43% for the 5, 10, and 20 g/L TX100 solutions, respectively. The enhanced solubilization of PHE by the addition of CS to TX100 solutions may be attributable to multiple factors, such as an increase of micellar size and hydrophobicity as well as to the formation of variously configured micelle-polymer aggregates. (C) 2010 Elsevier B.V. All rights reserved.