Background: Naphthalene is a polyaromatic hydrocarbon (PAH_s) present in many water sediments. This study evaluated the performance of UV/H₂O₂ reaction to decompose naphthalene in the aqueous solution.

Materials and Methods: It was an experimental-laboratory study. A one liter cylindrical glass reactor was used for performing all degradation experiments. The radiation source was a low pressure mercury UV lamp emitting at 254 nm (30 W, UV-C) which was placed above a batch photoreactor for UV/H₂O₂ experiments and different concentrations of H₂O₂ (5, 10, 15, 20, 25 and 30 mg/L) were tested.

Results: In 15 mg/L naphthalene in UV/H₂O₂ system and reaction times 5, 10, 20, 30, 40, 50, 60, 100 and 120 minutes, 15, 28, 31 , 36, 42, 52, 56, 73 and 59.5% naphthalene removal efficiencies were observed and COD removal efficiencies in reaction times 5, 10, 20, 30, 40, 50, 60, 100 and 120 minutes, 22, 38, 45, 61.5, 67.5, 70, 80, 88.5 and 76 % were observed. When the initial pH values were 3, 4, 5, 6, 7,9, 10 and 12 the naphthalene removal efficiency was approximately 75.8, 63.4, 62, 58.5, 44.8, 35.8 and 30%, respectively, with UV/H₂O₂ system.

Conclusion: The experimental results of this study suggested that the dosages with 20 mg/L H₂O₂ at pH= 3 with 2.8 W/cm² UV intensity (254 nm) provided the optimal operation conditions for the mineralization of naphthalene yielding a 73% mineralization efficiency after 100 minutes of reaction time.