Effects of nitrate on the advanced UV photolysis of di(2-ethylhexyl) phthalate degradation in aqueous solution

One of the objectives of this study was to delineate the effect of nitrate on the oxidation of di (2-ethylhexyl) phthalate (DEHP) by conducting bench-scale UV/H2O2 operations under a variety of UV doses and initial concentrations of H2O2 and NO3--N. Also, this study evaluated the two processes, UV alone and UV/H2O2, for DEHP oxidation. DEHP separation and quantification were performed using liquid chromatography-electrospray ionization tandem mass spectrometry system (LC-ESI-MS/MS). It was found that the UV photolysis of H2O2 is a more effective method of DEHP oxidation than the direct UV photolysis. It was observed that the DEHP oxidation efficiency of about 85.0% or higher could be achieved at a UV dose of 800 mJ/cm(2) with an initial H2O2 concentration of more than 30mg/L in the absence of nitrate. Nitrate hindered the DEHP oxidation by acting as (OH)-O-center dot scavengers. The adverse effect by nitrate in the UV/H2O2 process was significantly greater than that in the UV oxidation-alone, and its oxidation was almost reduced to half by nitrate under some operating condition. However, it is noted that the DEHP oxidation efficiency of more than 70% could be expected at a UV dose of 600 mJ/cm(2) with an initial H2O2 concentration of 50mg/L while considering the nitrate scavenging effect.