Background and purpose: Phthalate esters (PEs) are a large family of industrial chemicals widely used as plasticizers. Phthalates can cause endocrine disruption and cancers. Nowadays, phthalate esters are commonly used in cosmetics, adhesives and toy industries and simply get into the surface water and groundwater. The aim of this study was to evaluate the performance of UV / Na₂S₂O₈ / Fe²⁺ in DEP removal from aqueous solution.

Materials and methods: In this study the effect of pH, concentration of persulfate, Fe²⁺ concentration and contact time on removal of diethyl phthalate were studied in laboratory scale using a cylindrical-shaped reactor containing a UV-C lamp (16 watts) by batch method. The residual concentrations of Diethyl phthalate )DEP( were determined by HPL. The effects of independent parameters on DEP removal were evaluated by Multi simplex and the response surface method (box Behnken method).

Results: In this study the optimum condition was obtained at pH = 11, persulfate concentration of 0.4 Mmol/L, 0.07 Mmol/L Fe²⁺ and 90 minutes contact time. The results showed that the DEP removal by UV / Na₂S₂O₈ / Fe²⁺ process followed a first-order reaction kinetic.

Conclusion: The results indicated high efficiency of UV / Na₂S₂O₈ / Fe²⁺ process (95% removal under optimal condition) in removal of DEP from aqueous solutions. This efficiency demonstrates that this method is acceptable in DEP removal on industrial scale.