Degradation of trace aqueous 4-chloro-2-nitrophenol occurring in pharmaceutical industrial wastewater by ozone |
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Authors: | P. Gharbani M. Khosravi Ph.D S. M. Tabatabaii Ph.D K. Zare Ph.D S. Dastmalchi Ph.D A. Mehrizad |
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Affiliation: | 1. Department of Chemistry, North Tehran Branch, Islamic Azad University, Tehran, Iran 2. Department of Chemistry, Ahar Branch, Islamic Azad University, Ahar, Iran 3. Department of Chemistry, Science and Research Branch, Islamic Azad University, Tehran, Iran 4. School of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran
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Abstract: | Degradation of 4-chloro-2-nitro phenol by ozonation in aqueous solution was studied in a semi batch reactor under constant ozone dosage and variable pH conditions. The effectiveness of the process was estimated based on the degree of conversion of 4-chloro-2-nitro phenol. It was observed that ozonation is more effective at alkaline reaction of medium than other conditions. The degree of conversion achieved (at the first 5 minutes of the process)at pH 9 was 99.64% compared to 99.03% and 77.35% at pH 7 and 3, respectively. Another parameter used to quantify the 4-chloro-2-nitrophenol during ozonation was the pseudo first order rate constant k [min?1]. Results showed that the rate constant of the process was approximately much higher at the alkaline pH compared to acidic ones. A considerable improvement in chemical oxygen demand removal was observed at pH above 7. At pH 9, the reduction in chemical oxygen demand at the end of the process reached 56.9 %. The degree of organically bounded nitrogen conversion to nitrate was higher at pH 3. Of the total organic carbon reduction, 15.89 % was observed at pH 9. The 4-chloro-2-nitro phenol degradation intermediate products were analyzed by mass- spectrometry. The main intermediate product was chlorophenol. |
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