Background and aims: Polycyclic aromatic hydrocarbons (PAHs) are among the most toxic and carcinogenic, made up of two or more benzene ring. Also, due to low solubility and viable pollutants in the environment, they are in class Organic Pollutants Persistent (POPs). The most hazardous compound of this group is benzo (a) pyrene, the carcinogenicity of which has been approval by the World Health Organization. In this study, degradation of benzo (a) pyrene was examined using Photo-Fenton Oxidation Process and optimization of treatment conditions using experimental design.

Methods: In this experimental study, the effect of initial concentration benzo (a) pyrene 0.5, 1.5, 2.5, 3.5, 4.5 mg/L, optimal pH 3, exposure time 5, 15, 25, 35, 45 min, the amount of iron sulfate, 0.05, 0.15, 0.25, 0.35, 0.45 mM, and H₂O₂ levels 0.5, 1.5, 2.5, 3.5, 4.5 mM in Photo-Fenton process. 31 samples were determined using the central composite testing method. The concentration of benzo (a) pyrene was measured by high performance liquid chromatography (HPLC) device equipped with column C18. Data were analyzed using the software Design Expert.

Results: Results showed that the removal efficiency of benzo (a) pyrene increased with increases in iron sulfate, H₂O₂ ,and Exposure Time but it reduced with elevating benzo (a) pyrene concentration. A maximum removal efficiency of 93 percent was obtained in the following conditions: 3.5 mg/L of benzo (a) pyrene, 0.35 mM of iron sulfate, 2.9 mM of hydrogen peroxide, and an exposure time of 45 min.

Conclusion: According to the results, Photo Fenton process is an effective method to remove benzo (a) pyrene from the queous solution; with optimizing the effective operational parameters, these clean processes can be implemented in large-scale.