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

Abstract

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 . 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/cm² with an initial H₂O₂ concentration of more than 30 mg/L in the absence of nitrate. Nitrate hindered the DEHP oxidation by acting as OH scavengers. The adverse effect by nitrate in the UV/H₂O₂ process was significantly greater than that in the UV oxidationalone, 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/cm² with an initial H₂O₂ concentration of 50 mg/L while considering the nitrate scavenging effect.

Keywords:

• DEHP
• Hydroxyl radical
• Nitrate
• Scavenger
• UV/H₂O₂

Notes

Challenges in Environmental Science and Engineering, CESE 2011 25–30 September 2011, Tainan City, Taiwan