Photodegradation of nonylphenol by simulated sunlight

The photodegradation of nonylphenol (NP) was studied to simulate its photolysis process in natural seawater. The effects of the initial NP concentration, the light intensity, the temperature, the initial pH, the dissolved oxygen content and the presence of common water constituents (i.e., Fe(III), NO₃⁻ and HCO₃⁻) on the photodegradation of NP in pure water have been assessed. The degradation rate increased in the presence of Fe(III), NO₃⁻ or HCO₃⁻, and the photolysis rate of 4-NP was more rapid in alkaline solution than in an acidic medium. The DO content is a key factor in the photodegradation, and the rate of the photoreaction depended on the O₂ concentration. The degradation rate was slower in natural seawater than in pure water. 4-Nonylcatechol was identified as the intermediate of photodegradation of nonylphenol in natural seawater. The proposed pathway involved a reaction between irradiated NP and the reactive oxygen species that existed in the seawater.