Degradation of 17 alpha-ethinylestradiol in aqueous solution by ozonation

This study investigates the ozonation of 17 alpha-ethinylestradiol (EE2) in aqueous solution. The affecting factors on the degradation of EE2 were studied and described in details, such as initial EE2 concentration, initial pH value and ozone concentration. In addition, some parameters such as pH. electrical conductivity, mineralization efficiency and degradation products were monitored during the process. The mineralization efficiency of EE2 could reach 53.9%. During the ozonation process the rapid decrease of pH and the sharp increase of electrical conductivity indicated the fort-nation of acidic by-products, small fragments and ions which were confirmed by high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GUMS) analysis. Results showed that there were intermediate products of smaller molecule with higher polarity produced during the course of EE2 degradation. Then a possible reaction pathway for EE2 degradation involving all intermediates detected is proposed. During the ozonation process EE2 was first oxidized into hydroxyl-semiquinone isomers which were subsequently degraded into low molecular weight compounds such as oxalic acid, malonate, glutarate, and so on. Furthermore. these organic acids are easily oxidized by ozone into carbon dioxide (CO2). This work shows that ozonation process is promising for the removal of EE2. The results can provide some useful information for the potential treatment of EE2 by ozonation in aqueous solution. (c) 2005 Elsevier B.V. All rights reserved.

Ozonation of the purified hydrolyzed azo dye Reactive Red 120 (CI)

The combination of chemical and biological water treatment processes is a promising technique to reduce recalcitrant wastewater loads. The key to the efficiency of such a system is a better understanding of the mechanisms involved during the degradation processes. Ozonation has been applied to many fields in water and wastewater treatment. Especially for effluents of textile finishing industry ozonation can achieve high color removal, enhance biodegradability, destroy phenols and reduce the COD. However, little is known about the reaction intermediates and products formed during ozonation. This work focuses on the oxidative degradation of purified (>90%), hydrolyzed Reactive Red 120 (Color Index), a widely used azo dye in the textile finishing processes with two monochlorotriazine anchor groups. Ozonation of the dye in ultra pure water was performed in a laboratory scale cylindrical batch reactor. Decolorization, determined by measuring the light absorbance at the maximum wavelength in the visible range (53 5 nm), was almost complete after 150 min with an ozone concentration of 12.8 mg/l. The TOC/TOC0 ratio was about 74% and the COD was diminished to 46% of the initial value. The BOD5/COD ratio increased from 0.01 to 0.14. To obtain detailed information on the reaction processes during ozonation and the resulting oxidation products organic and inorganic anions were analyzed. Oxidation and cleavage of the azo group yielded nitrate. Cleavage of the sulfonic acid groups of aromatic rings caused an increase in the amount of sulfate. Formic acid and oxalic acid were identified as main oxidation products by high performance ion chromatography (HPIC). The concentrations of these major products were monitored at defined time intervals during ozonation.